M. LAKSHMI PRASAD - Shodhgangashodhganga.inflibnet.ac.in/bitstream/10603/33375/1/srama... · 2018-07-02 · Embedded C is a popular programming language for microcontroller based

DESIGN AND DEVELOPMENT OF EMBEDDED BASED PHOTOACOUSTIC

SYSTEM FOR THE MEASUREMENT OF AIR POLLUTANTS IN

INDUSTRIAL AND AUTOMOBILE EMISSIONS

Thesis submitted to

SRI KRISHNADEVARAYA UNIVERSITY ANANTAPUR - 515 003 (A.P) INDIA

By

M. LAKSHMI PRASAD

In partial fulfillment for the award of the degree of

DOCTOR OF PHILOSOPHY IN

INSTRUMENTATION

Under the Supervision of

Prof. K. MALAKONDAIAH

DEPARTMENT OF INSTRUMENTATION SRI KRISHNADEVARAYA UNIVERSITY ANANTAPUR – 515 003

JANUARY 2013

“I have heard articulate speech by sunlight! I have heard a ray of the sun laugh

and cough and sing! ...I have been able to hear a shadow and I have even

perceived by ear the passage of a cloud across the sun's disk”

-Alexander Graham Bell

DEDICATED

TO

MY FATHER

SRI KRISHNADEVARAYA UNIVERSITY Anantapur - 515 003, A.P., INDIA

Prof. K. MALAKONDAIAH, M.Sc., Ph.D. (Retd)

Department of Instrumentation and

University Science Instrumentation Centre

Sri Krishnadevaraya University

Anantapur -515 003

Office : 08554 -255881

Res : 08554 -244150

Email : [email protected]

CERTIFICATE

This is to certify that the thesis entitled “Design and Development of Embedded

Based Photoacoustic System for the Measurement of Air Pollutants in Industrial

and Automobile Emissions” submitted by Mr. M. Lakshmi Prasad is a bonafied

record of the research work done by him during the period of study under my

supervision, and that it has not previously performed the basis for the award of any

degree, diploma, associateship, fellowship or other similar titles to the candidate.

Date : Prof.K. MALAKONDAIAH

Place : Anantapur Research Supervisor

DECLARATION

I declare that the thesis entitled “Design and Development of Embedded Based

Photoacoustic System for the Measurement of Air Pollutants in Industrial and

Automobile Emissions” submitted for the award of Doctor of Philosophy in

Instrumentation is entirely new and original and has not submitted to any other

University for the award of any other degree or diploma.

Date :

Place : Anantapur (M. LAKSHMI PRASAD)

Research Scholar

Department of Instrumentation

Sri Krishnadevaraya University

Anantapur-515 003

CONTENTS

PREFACE i

Chapter 1 : Introduction

1.1 Introduction to air pollutants 1

1.2 Introduction to photoacoustic spectroscopy 6

1.3 A brief review of earlier experimental techniques 8

1.4 Role of embedded systems in Instrumentation 18

1.5 Purpose and scope of the present study 28

References 30

Chapter 2: Design and Development of Embedded Based Photoacoustic

Measurement System: Hardware Design

2.1 Principle 33

2.2 Functional block diagram 35

2.3 Radiation source 36

2.4 Modulator for radiation source 39

2.5 Photoacoustic cell 42

2.6 Acoustic detector 49

2.7 Low noice pre-amplifier 51

2.8 Lock-in amplifier unit 53

2.9 Temperature sensing unit 58

2.10 Pressure sensing unit 60

2.11 Analog to digital converter 62

2.12 ARM Microcontroller unit 65

2.13 Liquid crystal display 68

2.14 Power supply unit 72

2.15 Schematic diagram and working 73

2.16 Sample handling unit 75

References 76

Chapter 3 : Design and Development of Embedded Based Photoacoustic

Measurement System: Software Development

1. Salient features of embedded C language 78

2. Software development 87

3. Program in detail 93

3.4 Calibration and measurement procedure 102

References 104

Chapter 4 : Standardization of Embedded Based Photoacoustic Measurement

System

4.1 Introduction to standardization 105

4.2 Response of the photoacoustic resonant cell 106

4.3 Standardization of the system with nitrogen dioxides 108

4.4 Results and discussion 110

References 117

Chapter 5 : Measurement of Nitrogen Oxides in Industrial Emissions

Industrial emissions 118

Nitrogen oxides pollutant 122

Experimental procedure 126

Results and discussion 127

References 130

Chapter 6 : Measurement of Carbon Soot Pollutant in Automobile

Emissions

Automobile emissions 131

Carbon soot pollutant 133

Calibration and measurement procedure 136

Results and discussions 139

References 142

Chapter 7: Measurement of Carbon Monoxide Pollutant in Industrial and

Automobile Emissions

1. Industrial and automobile emissions 143

2. Introduction to carbon monoxide 146

3. Calibration and measurement procedure 149

4. Results and discussion 152

References 157

PREFACE

Instrumentation, a central feature for all scientific and technological activities, plays a

pivotal role in all aspects of human endeavor. The photoacoustic spectroscopy, a new

impetus to the field of analytical sciences, with the combined features of laser sources

and sensitive photoacoustic detection system offers a great potential for pollution

monitoring. The advent of embedded processors further has enhanced the design of

these instruments which improves their quality and versatility.

One of the most concerning problems faced by the modern society is the

atmospheric pollution which causes dangerous environmental hazards such as the

degeneration of air quality, acid rain, photochemical smog, ozone layer depletion, health

diseases and the global warming. Air pollution in India has been aggravated over the

years due to the growing cities, increasing traffic, rapid economic development and

industrialization and higher levels of energy consumption. In India, air pollution is

restricted mostly to urban areas, where automobiles are the major contributors, and to a

few other areas with a concentration of industries and thermal power plants. The major

sources of air pollution in the country are industries (toxic gases), thermal power plants

(fly ash, oxides of nitrogen, carbon monoxide and sulphur dioxide), and motor vehicles

(carbon monoxide, soot particles, hydrocarbons and oxides of nitrogen).

No doubt, several investigators have developed the techniques for measurement

of air pollutants in different emission zones and several manufacturers produced a

variety of instruments for different pollutant estimations. But these are conventional,

indirect methods and suffer from many disadvantages. Hence, in the present study, an

attempt is made to design and fabricate an embedded based photoacoustic system for

measurement of air pollutants such as nitrogen oxides, carbon soot and carbon

monoxide in industrial and automobile emissions.

The work presented in the thesis is divided into seven chapters, each chapter

being sub-divided into several sections. The first chapter is introductory. In section

1.1, the air pollutants and their environmental and health effects are discussed. The

section 1.2 explains the basic principles and brief history of photoacoustic

spectroscopy. A brief review of earlier experimental techniques for air pollutants is

presented in section 1.3. The role of embedded instruments in instrumentation is

given in section 1.4. The section 1.5 deals with the purpose and scope of the present

study.

Chapter 2 deals with the hardware design aspects of embedded based

photoacoustic system for measurement of air pollutants. The principle of working of the

system is explained in section 2.1. The functional block diagram of the system is

presented in section 2.2. The laser radiation sources employed in the present study are

described in section 2.3. The XR 2206 is an on-chip function generator which serves as

a modulator for laser source is designed in the present study. The details are given in

section 2.4. The photoacoustic cell is the heart of the photoacoustic spectrometer that

deserves a special attention in its design. The design and fabrication details of a

photoacoustic cell are explained in section 2.5. A high sensitive professional electret

microphone is used as an acoustic detector in the present study whose details are

presented in section 2.6. The design features of low noise preamplifier are presented in

section 2.7. The lock-in amplifier which contains four different sections - preamplifier,

bandpass filter, phased lock loop and phase sensing detector plays a significant role. The

design features are described in section 2.8. The sections 2.9 and 2.10 are devoted for

temperature and pressure sensing units which are essential to monitor temperature and

pressure in the system. The details of high speed analog to digital converter and its

salient features are given in section 2.11. The ARM 32-bit microcontroller LPC2106 is

used as an embedded processor in the present study. The hardware details along with its

interfacing mechanism are explained in section 2.12. The section 2.13 gives the details

of 20x4 characters liquid crystal display unit and its interfacing with the embedded

microcontroller. The regulated power supply which supplies the required power to all

the functional units of the system is designed in the present study and it is explained in

section 2.14. The schematic diagram, construction and its working details are presented

in section 2.15. The section 2.16 gives the details of sample handling system.

Chapter 3 is devoted for software development of the present study.

Embedded C is a popular programming language for microcontroller based systems.

The section 3.1 deals with the salient features of embedded C language. The section 3.2

describes the software development such as software routines and flow charts of the

system designed in the present study. The program, in detail, is given in section 3.3.

The calibration and measurement procedures are explained in section 3.4.

Chapter 4 deals with the calibration of the system. The section 4.1 is

introductory. The response of photoacoustic resonance cell is discussed in section

4.2. The standardization of the system with standard nitrogen dioxide samples is

explained in section 4.3. The results of measurements are presented section 4.4.

Chapter 5 deals with the application of the system for measurement of nitrogen

oxides (NOx) pollutant in industrial emissions. NOx is one of the most prominent air

pollutants and poison by inhalation. Some of the industries of Hyderabad and Ranga

Reddy district area are chosen for the measurement of nitrogen oxides with the system

developed in the present study. The common industrial emissions and their contribution

to pollution are discussed in section 5.1. The significance of nitrogen oxides as

pollutants is given section 5.2. The experimental procedure for nitrogen oxides pollutant

is described in section 5.3. The results of measurements are presented in section 5.4.

Chapter 6 deals with the application of the system for measurement of carbon

soot pollutant in industrial and automobile emissions. Carbon soot plays a major role in

environmental degradation and global warming. Some of the industries and automotive

vehicles emissions of Hyderabad and Ranga Reddy district area are chosen for the

measurement of carbon soot with the system developed in the present study. The section

6.1 gives the introduction about automobile emissions. The significance of carbon soot

as pollutant is given section 6.2. The calibration and measurement procedure for carbon

soot pollutant is described in section 6.3. The results of measurements are presented in

section 6.4.

Chapter 7 deals with the application of the system for measurement of carbon

monoxide pollutant in industrial and automobile emissions. Carbon monoxide is a

colorless, odorless and tasteless gas which is highly toxic to human being and animals.

Some of the automotive vehicles of Hyderabad area are chosen for the measurement of

carbon monoxide with the system developed in the present study. The industrial,

automobile emissions and their contribution to pollution are discussed in section 7.1.

The significance of carbon monoxide as pollutant is given section 7.2. The calibration

and measurement procedure for carbon monoxide pollutant is described in section 7.4.

The results of measurements are presented in section 7.5.

The embedded based photoacoustic system designed and developed in present

study is quite successful in the measurement of air pollutants - nitrogen oxides, carbon

soot and carbon monoxide in the given samples of industrial and automobile emissions

with an accuracy of ±1ppm.

I convey my deep sense of gratitude to my beloved teacher and research

supervisor Prof. K. Malakondaiah (Retd), University Science Instrumentation Centre

and Department of Instrumentation, Sri Krishnadevaraya University, Anantapur for his

valuable guidance and constant encouragement in carrying out my research work.

I am very thankful to Prof. C. Nagaraja, Head, Department of Instrumentation,

Sri Krishnadevaraya University, Anantapur for his help and encouragement. I am

thankful to Dr. S. Allahbaksh (Retd), Prof. B. Rama Murthy and Prof. K. Nagabhushan

Raju, Department of Instrumentation and University Science Instrumentation Centre,

Sri Krishnadevaraya University, Anantapur for their helpful suggestions. I am grateful

to Prof. P. Bhaskar, Gulbarga University Postgraduate Center, Raichur, Karnataka state

for his valuable suggestions and help.

I convey my deep sense of gratitude to Sri Ramesh Datla, Managing Director,

ELICO Limited, Hyderabad for his kind cooperation, encouragement and generous

support to carry out my research work. My sincere thanks are due to Sri K.V.S.N. Raju,

Sri J.P. Reddy, Dr. Gayatri Hela, Sri K.V.S.K. Prasad and Sri N.J.R. Srinvas,

Department of Technology Services, ELICO Limited, Hyderabad for their helpful

suggestions. I am thankful to Dr. G. Satheesh Babu, BPL Limited, Bangalore for his

valuable suggestions.

I am thankful to my beloved wife Mrs. P. Anuradha and other family members for

their continuous cooperation and support in carrying out my research work. Words

cannot express my deep sense of gratitude to my mother and brother for their support

and encouragement.

I express my sincere thanks to my research colleagues in the Department of

Instrumentation - Mr. Ramana, Mr. Raja Rao, Mrs. Anjulatha, Mr. Ashok, Mr. Anand,

Mrs. P. Sushama, Miss V. Sailaja and other research scholars for their cooperation and

help..

I am very grateful to the authorities of Sri Krishnadevaraya University,

Anantapur and M/s ELICO Limited, Hyderabad for providing me the necessary

facilities to carry out my research work.

M. LAKSHMI PRASAD

CHAPTER 1

Introduction

Section 1.1

INTRODUCTION TO AIR POLLUTANTS

Clean air is most important to human beings, because we cannot live without air for

more than a few minutes. There are many substances in the air which are harmful to the

health of human being, animals and plants. Harmful substances are arising day-to-day

from human activities and natural processes. However these substances are found

greater concentration in the air as a result of human activities which are generally

referred as air pollutants1. The air pollutants cause severe health disorders in human

being. It is necessary to analyze the air pollutants and take the necessary precautions.

The measurement of air pollutants in air is very essential to warn and educate the people

on its toxic effects.

The air pollutants can be classified into two categories primary air pollutants and

secondary air pollutants. The primary air pollutants are substances that directly emit into

the atmosphere from volcanic2 explosion and secondary air pollutants do not emit

directly which form when the primary pollutants interact with other pollutants. The

most of air pollutants produce from human activities which are briefly described.

1. Nitrogen dioxide pollutant

Nitrogen dioxide (NO2) is one of the several nitrogen oxides. It is a reddish-brown,

pungent and acidic gas which is corrosive and strongly oxidizing. Nitrogen dioxide (3,4)

is one of the most prominent air pollutants and poison by inhalation. It does not usually

release directly into the air, which forms in the air when nitrogen oxide react with other

chemicals. The main source of nitrogen dioxide is the combustion of fossil fuel such as

coal, oil, gas etc. In cities, motor vehicles are contributing about 80% of ambient

nitrogen dioxide. Nitrogen dioxide causes smog and acid rain.

2. Carbon monoxide pollutant

Carbon monoxide(5,6)

is a colorless, odorless and tasteless gas which is highly toxic to

human beings and animals. It consists of one carbon atom and one oxygen atom. It

produces from incomplete combustion of carbon based fuels such as petrol, diesel,

wood etc. Motor vehicles produce carbon monoxide about 60 percent of carbon

monoxide nationwide. In cities, it may be as high as 90 percent. Other sources include

industrial processes, non-transportation fuel combustion and wildfires.

Carbon monoxide enters the bloodstream through the lungs and reduces oxygen

delivery to the body's organs and tissues. The health threat7 from carbon monoxide at

low levels is most serious for those who suffer from cardiovascular disease, such as

angina pectoris. At much higher levels, carbon monoxide can be poisonous. Even

healthy people may be affected. Visual impairment, reduced work capacity, reduced

manual dexterity, poor learning ability and difficulty in performing complex tasks are

all associated with exposure to carbon monoxide.

3. Sulfur dioxide pollutant

Sulfur dioxide (SO2) is a colorless gas. It belongs to the family of sulphur oxides(8,9)

.

Sulfur dioxide reacts on the surface of airborne solid particles. It is soluble in water and

it can be oxidized within airborne water droplets. The most important man-made

sources of sulphur dioxide are fossil fuel combustion, smelting, manufacture of sulfuric

acid and conversion of wood pulp to paper production. The coal burning is largest man-

made source of sulphur dioxide accounting for about 50% of annual emissions. The

major health effects are respiratory illness, pulmonary disease and cardiovascular

disease. In the atmosphere, sulphur dioxide mixes with water vapor producing sulphuric

acid which can be transported by wind over many hundreds of kilometers and

deposited. Sulfur dioxide causes acid rains.

4. Carbon dioxide pollutant

Carbon dioxide (CO2) is a colorless gas. It contains two oxygen atoms and single carbon

atom. CO2 is a odorless at low concentrations. It has a sharp and acidic odor at higher

concentrations. Carbon dioxide10

is obtained from the combustion of coke/coal or other

carbon containing fuels

C + O2 → CO2

In most of the areas, carbon dioxide is generated as a by-product of the combustion of

fossil fuels such as coal, oil, natural gases and other chemical processes. Carbon dioxide

acts as an asphyxiant and an irritant when inhaled at higher concentrations than usual

atmospheric levels. It can produce a sour taste in the mouth and a stinging sensation in

the nose and throat.

5. Carbon soot pollutant

Carbon soot is one of the air pollutants. It is a general term that refers to impure carbon

particles resulting from the incomplete combustion of a hydrocarbon. Carbon soot(11,12)

is in the general category of airborne particulate matter which is considered hazardous

to the lungs and general health, when the particles are less than five micrometers in

diameter such particles are not filtered out by the upper respiratory tract. Carbon soot

emits from various sources such as internal combustion engines, power plant boilers,

ship boilers, central steam heat boilers, waste incineration, local field burning, house

fires, forest fires, furnaces etc.

6. Ozone pollutant

Ozone (O3) is a triatomic molecule which consists of three oxygen atoms. The

ozone(13,14)

occurs naturally in the upper layers of the atmosphere. Ozone is an

important gas which shields the earth from harmful ultraviolet rays of the sun. However,

ozone is an air pollutant and highly toxic gas at the ground level. It causes itching and

burning of our eyes. It also reduces our resistance to cold and pneumonia. The motor

vehicles and industrial emissions are the major cause to increase the ground-level

ozone.

7. Suspended particulate matter

Suspended particulate matter(11,15)

are tiny particles of solid or liquid matter suspended

in air. The tiny particles are less than 10µm in diameter which tend to stay suspended in

the atmosphere for a long period of time. These fine particulates (16-17)

are small enough

to bypass the screening of the nose. They can penetrate alveoli and deposit in the upper

respiratory tract. The large number of deaths and other health problems are associated

with particulate matter. Particulate matter has been emitting from fuel combustion in

motor vehicles, process combustion and industrial exhaust. They also are formed from

reactions of other pollutants like NOx, SO2 and hydrocarbons.

Emission sources of air pollutants

The different emission sources emit air pollutants into atmosphere in the form of gases.

They can be classified into the following two major categories

2. Anthropogenic emission sources

3. Natural emission sources

Anthropogenic emission sources

Anthropogenic describes something that is made by human beings. Anthropogenic

emission sources are mostly related to burning of various kinds of fuel which are

described as follows

(i) Stationary sources18

, which include smoke stacks of power plants,

manufacturing industries and municipal waste furnaces.

(ii) Mobile sources19

such as motor vehicles, aircraft, container ships and related

port air pollution.

(iii) Fumes, which generates from paint, hair spray, varnish, aerosol sprays and other

solvent manufacturing industries.

(iv) Military such as nuclear weapons, toxic gases, germ warfare and rocketry.

Natural emission sources

(i) Methane, which emits from the digestion of food of animals.

(ii) Smoke and carbon monoxide, which emit from wildfires.

(iii) Volcanic activity, which produces sulfur, chlorine and ash particulates.

(v) Dust, which can form from natural sources usually large areas of land with little

or no vegetation

Section 1.2

INTRODUCTION TO PHOTOACOUSTIC SPECTROSCOY

Photoacoustic spectroscopy (PAS) is based on the absorption of electromagnetic

radiation by analyte molecules. Non-radiative relaxation processes20

lead to local

warming of the sample matrix. The pressure fluctuations are generated by thermal

expansion, which can be detected in the form of acoustic waves.

The photoacoustic effect was discovered by Alexander Graham Bell(21-22)

in

1880. He found that thin discs emit sound when exposed to a rapidly interrupted beam

of sunlight. By placing different absorbing substances in contact with the ear using a

hearing tube, he was able to detect absorption in both the visible and the invisible

regions of the solar spectrum. This spectrophone was used in his experiments on

wireless transmission of sound. After additional experiments are done by Tyndall and

Rontgen and some initial analytical applications in the year of 1930 and interest in the

photoacoustic effect declined over the following decades. The first applications of the

effect to trace gas monitoring were reported in the late 1960. Important steps leading to

this rediscovery of the effect for analytical purposes were the invention of the laser as

an intense light source and the development of highly sensitive sound detectors such as

condenser microphones and piezoelectric transducers. The first comprehensive

theoretical description of the photoacoustic effect was found in solids by Rosencwaig

and Gersho23

(R&G) theory.

In the 1970s and 1980s photoacoustic gas detection24

is boomed. The high

sensitivities are achieved by using the gas lasers and solid state laser such as CO, CO2

and DPSS lasers in photoacoustic systems. The high output power and their line

tunability to be ideal sources to push the sensitivity of photoacoustic (PA) gas detection

into the ppbV (parts per billion volume) concentrations or even below.

Photoacoustic effect

The photoacoustic effect is a conversion between light and acoustic waves due to

absorption and localized thermal excitation25

. When rapid pulses of light are incident on

a sample of matter, they can be absorbed and the resulting energy will be radiated as

heat. This heat causes detectable sound waves26

due to pressure variation in the

surrounding medium. With the invention of the microphone and laser, the photoacoustic

effect took on new life as an important tool in spectroscopic analysis and continues to

be applied in an increasing number of fields. The mechanism and sequence steps of the

photoacoustic signal generation process is shown in Fig. 1.1 and Fig1.2.

Section 1.3

A BRIEF REVIEW OF EARLIER EXPERIMENTAL TECHNIQUES

Photoacoustic Spectroscopy (PAS) works on the photoacoustic effect discussed in

earlier section. Photoacoustic spectroscopy is a new technique recently being used as a

potential tool which finds applications in almost all disciplines of Science and

Technology.

A variety of methods have been employed for the estimation of air pollutants

such as nitrogen oxides27

(NOx), carbon monoxide (CO), carbon soot16

, sulfur oxides

(SOx), carbon dioxide (CO2), volatile organic compounds17

(VOC), particulate matter

(PM) and toxic metals. Traditional methods for estimation of air pollutants are photo-

ionization, IR spectrophotometer, chromatography, gas analyzers etc.. Many of these

methods suffer from interferences, selectivity, sensitivity and dynamic range. They can

be labor intensive and often difficult to automate. Multiple elements can be determined

by adding additional channels to the system. However, this adds complexity and cost to

the instrument.

The analysis of air pollutants is a very difficult task despite the appearance of

new methods. The following are different methods that are in use for the estimation of

air pollutants.

1. Photo-ionization detector

2. Flame ionization detector

3. Infrared spectroscopy

4. Fourier Transform Infrared analyzer

5. Gas chromatography

6. Metal oxide semiconductor sensors and

7. Aethalometer

Photo-Ionization Detector

Photo-ionization detector is an instrument which is used to detect the volatile organic

contaminants28

(VOCs). It is an efficient detector for many gases and vapor analytes.

High energy light sources typically ultraviolet (UV) range are used to break molecules

into positively charged ions. The targeted gas molecules absorb the energy of UV light

and are ionized, which forms as positively charged ions. The process of ionization is

as follows

RH + hυυυυ RH+ + e-

hυυυυ is a photon energy, which has greater or equal than ionization energy of species RH.

The targeted gas molecules get electrically charged and produce the ions as an electric

current, which is the final output signal of the detector. The greater concentration of the

element produces more current. The output current is amplified and final data presented

on the display. This method is expensive and time-consuming.

Flame Ionization Detector

Flame ionization detector29

(FID) is a powerful analytical instrument which is employed

to detect organic and inorgnic compounds. Hydrogen flame is used as the source of

ionization energy. FID is able to detect nearly all-organic compounds. In clean air, the

hydrogen flame is free from ions and non-conducting. Organic contaminants containing

either a carbon-hydrogen or carbon-carbon bond break down according to the following

reaction when exposed to the hydrogen flame in the ionization chamber.

RH + O RHO+ + e- + CO2 + H2O

Positively charged carbon containing ions are collected on a negatively charged plate.

The ion current is proportional to the hydrocarbon concentration.

A major difference between FID and PID detection is the amount of variance in

sensitivity from one organic substance to another. The amount of energy (ionization

potential) is necessary to remove an electron to create a charged fragment which

determines the sensitivity of a PID detector to a specific molecule. The shape, size

and specific chemical bonds present within the molecule determine the Ionization

potential (IP). Ionization potential varies widely from one substance to the next. For

these reasons, the sensitivity of a PID detector also varies widely from one substance

to the next.

FID sensitivity does not vary as significantly from one organic substance to

another because the amount of energy necessary to break specific carbon-carbon or

carbon-hydrogen bonds is relatively constant. For this reason FID sensitivity is more

generalized and varies much less significantly between one hydrocarbon and another.

Another very important difference between the two detection techniques is that FID can

detect methane while PID can not detect. FID has traditionally been the preferred

instrument for detection of methane and other saturated alkanes as well as unsaturated

hydrocarbons and alkenes at parts per million levels. Hydroxyl (OH-) or chloride (Cl-)

functional groups tend to reduce sensitivity while inorganic contaminants such as

chlorine, ammonia and hydrogen cyanide are not detected. FIDs are best for easily

flammable components. However, FID destroys most of components and no further

detection is possible.

Infrared Spectroscopy

Infrared spectroscopy(30,31)

is one of the most powerful analytical techniques, which

offers the possibility of chemical identification. IR technique when coupled with

intensity measurements may be used for quantitative analysis. Infrared spectroscopy has

been of tremendous use to chemists and it is currently more popular as compared to

other physical techniques (X-ray diffraction, electron spin resonance, etc.,) in the

elucidation of the structure of unknown compounds. The infrared radiation refers

broadly to that part of the electromagnetic spectrum which lies between the visible and

microwave regions. The infrared region of the spectrum encompasses radiation with

wave numbers ranging from about 12,800 to 10 cm-1

or wavelengths from 0.78 to 1000

urn. From instrumentation and application point of view, the infrared region has been

subdivided into near IR region32

(overtone region), mid IR region (vibration rotation

region) and far IR region (rotation region). The techniques and the applications of

methods based upon the three infrared spectral regions differ considerably. An infrared

spectrum shows downward peaks corresponding to absorption, plotted against

wavelength (λ) or wave number (ϋ). In the infrared spectrum, apart from the prominent

modes of vibrations, there are other vibrations due to coupling and overtones that may

lead to additional bands in the spectrum.

The various bands can be interpreted according to the characteristics functional groups

present in the compound. Infrared absorption, emission and reflection spectra for

molecular species can be rationalized by assuming that they all arise from various

changes in energy state brought about by transitions of molecules from one vibrational

or rotational energy state to another.

Absorption of infrared radiation is thus confined largely to molecular species

that have small energy differences between various vibrational and rotational states. In

order to absorb infrared radiation, a molecule must undergo a net change in dipole

moment as a consequence of its vibrational or rotational motion. Only under these

circumstances can an alternating electrical field of the radiation interact with the

molecule and cause changes in the amplitude of one of its motions.

The basic components of an infrared spectrometer are radiation source,

monochromator, detector, amplifier and recorder. A radiation source provides radiation

over the entire range of the infrared spectrum. The monochromator disperses33

the light

and then selects a narrow wave number range. The detector measures the energy and

transforms it into an electric signal. This signal is further amplified and registered by the

recorder. The IR spectra of most of the contaminant air samples were recorded in mid

and far IR region and are used for the investigation. Typical applications of IR

spectrometer include monitoring for the presence of anesthetic gases and organic

solvents such as nitrous oxide, nitrogen dioxide, halothane, toluene, carbon dioxide,

carbon monoxide as well as many other organic compounds. This method consumes

time for sample preparation and it cannot give information in detailed.

Fourier Transform Infrared Spectroscopy

Fourier transform infrared (FTIR) spectroscopy is a technique which is used to obtain

an infrared spectrum of absorption and emission of a liquid or gas. FTIR spectrometer

simultaneously collects spectral data in a wide spectral range. The fourier transform

infrared34

spectrograph have replaced the conventional infrared spectrograph. A FT-

Infrared spectrometer consists of two parts: (a) An optical system, which uses an

interferometer and (b) A dedicated computer which stores data, performs computations

on data and plots the spectra. It consists of two perpendicular mirrors; one of which is a

stationary mirror and other a movable mirror which can be displaced perpendicularly to

the fixed mirror at a constant velocity. Between these two mirrors is beam splitter set at

45° from the initial position of the movable mirror. A parallel beam of radiation from an

infrared source is passed to the mirrors through the beam splitter. The beam splitter

reflects about half of the beam to the fixed mirror, which reflects it back to the beam

splitter and transmits the other half to the movable mirror, which reflects it back to the

beam splitter. The returning beams are again split and mixed about half going back to

source and half passing through the sample compartment. The composition of the beam

splitter depends on the spectral region of interest. For example in the mid-infrared

region (4000-400 cm-1

), a beam splitter of germanium coated on KBr plate (substrate) is

often used. Germanium reflects the radiation while Kbr transmits most of the desirable

radiation. In the far infrared region, germanium coated on CSI (800-200 cm-1

) or

germanium coated on Mylar (polyethylene terephthalete) (650-10 cm-1

) are used as

beam splitters. A thin film of the beam splitter material is coated on an optically flat

substrate. The return beams from both the mirrors along the same path length as their

incident path are recombined into a single beam at the beam splitter. The path length of

one of the return beams is changed in order to create phase difference to cause an

interference pattern. The recombined radiation is then directed through the sample and

focused on to the detector. The detector measures the amount of energy at discrete

intervals of mirror movement. The movable mirror can be moved in a range of say ± 5

cm. The mirror velocities from 0.05 to 5 cm-1

are used. Interferometer instruments need

detectors with response times short enough to detect and transmit rapid changes to the

recorder. The detector used in conjunction with rapid scanning interferometers in the

mid-infrared region is triglycine sulfate with KBr windows as pyroelectric bolometer. It

has a high response time. Other most common detectors used such as thermocouples,

bolometers and Golay detectors which have short response time. This method is not

suitable to measure spectra. It measures interferogram only.

Gas Chromatography

Gas chromatography

35 is a method for separating the components of a gas or liquid and

measuring their relative quantities. It is a useful technique for chemicals that do not

decompose at high temperatures and when a very small quantity of sample is available.

The use of gas chromatography is limited by the decomposition temperature of the

components of the mixture and the composition of the column. Most columns cannot

withstand temperatures greater than 250-350°C.

In gas chromatography, a sample is rapidly heated and vaporized at the injection

port. The sample is transported through the column by a mobile phase consisting of an

inert gas. Sample components are separated based on their boiling points and relative

affinity for the stationary phase, which is most often a viscous liquid within the column.

The higher a components affinity for the stationary phase, the slower it comes off the

column. The components are then detected and represented as peaks on a

chromatogram. This method is time taking. Also, it is difficult to measure and inject

such small samples (approx 0.3microlitres) accurately without evaporation of the

sample.

Metal oxide semiconductor sensors

Metal Oxide Semiconductor36

(MOS) sensors are application specific gas sensors which

use metal oxide based sensing thick films deposited onto a Si-micro-machined

substrate. The substrate contains electrodes which measure the resistance of the sensing

layer, and a heater that heats the sensing layer from 200°C to 400°C. The sensor

responds to changes in the composition of the ambient atmosphere with a change in the

resistance of the sensing layer. A large number of toxic and explosive gases can be

detected even at very low concentrations. MOS sensors detect a wide range of gases

such as carbon monoxide (CO), nitrogen oxides (NO2), ammonia (NH3), hydrogen

sulfide (H2S), methane (CH4) and a wide variety of volatile organic compounds

(VOCs).

The working principle of the MOS is the changes in composition of the ambient

atmosphere will determine changes in resistance of the sensing layers. In practice, the

relationship between sensor resistance and concentration of the target gas usually

follows a power law. Over a large range of concentrations, it can be described as

follows

R= Kc+n

R is the resistance of the sensing layer, c is the concentration of the target gas, K is a

measurement constant and n has values between 0.3 and 0.8. The positive sign of n is

used for oxidizing gases and the negative sign for reducing gases.

MOS sensors have been used extensively to measure and monitor trace amounts

of environmentally important gases such as carbon monoxide and nitrogen dioxide.

They are susceptible to humidity which cause drift on analysis. Low stability and long

range drift are important issue in this method.

Aethalometer

The aethalometer is an instrument which offers a real-time readout of the concentration

of black or elemental carbon particles in the air stream. The carbon particles emit from

all types of combustion most notably from diesel engine exhaust. The aethalometer uses

a continuous filtration and optical measurement method to give a continuous readout of

real-time data. It contains a sampling port that may be preceded by size-selective inlet

for the measurement of elemental particles in a specified aerodynamic size fraction.

The optical measurement method for black carbon is consistent and

reproducible. A wide body of published research shows that the aethalometer black

carbon measurement is closely proportional to filter-based elemental carbon

measurements. The aethalometer performs the optical analysis and data readout on-site.

However, this method is expensive and time consuming.

In the present system, a simple, significant photoacoustic cell, novel

acoustic detectors and 32-bit microcontroller based system for the measurement of air

pollutants are designed and developed. Photoacoustic is direct technique for trace gas

analysis. It is novel in the sense of low-level concentrations while most of the existing

techniques such as conventional and indirect methods. This technique plays an

important role in increase signal to noise ratio and plays significant role in

instrumentation.

Section 1.4

ROLE OF EMBEDDED SYSTEMS IN INSTRUMENTATION

Instrumentation(37-38)

is a technology of measurement and control which serves not only

science but also all branches of engineering, medicine and etc. Now a days embedded

system is a very powerful tool in instrumentation (measurement and control) systems.

The advanced embedded based measurement is fast, highly reliable, precise, accurate

and all flexible to make it perfectly for any given task. An embedded system is a

computing system that is embedded inside of a product, for example a computing

system is dedicated to controlling some non-computing hardware like washing machine,

a car engine or a missile. Computing machines were always the attraction for fast

development of science and technology in the field of automation for industrial and

domestic products. Automation being one of the objectives, the computational needs

was the motivation for the development of computing machines and devices. The

computing system is part of procedure or process. The most important component in an

embedded system is the microprocessor or microcontroller.

Microcontroller

39 is an electronic single chip microcomputer that is more

suited for measurement and control of instruments. Microcontroller has been treated as

a tool for computing and communication with other devices. Knowledge of

microcontrollers is meaningful and very rewarding if it is applied to design a product

that is useful in the industry or for the society in general. Microcontrollers are more

suited for control and automation of process, analytical, biomedical industries and etc.

There are two types of architectures available namely, Harvard architecture and Von

Neumann architecture.

Harvard architecture

Harvard architecture uses separate memories for program and data with their

independent address and data buses. Because of two different streams of data and

address, there is no need to have any time division multiplexing of address and data

buses. The more designs of microcontrollers are followed by Harvard architecture. Not

only the architecture supports parallel buses for address and data, but also it allows a

different internal organization such that instruction can be pre-fetched and decoded

while multiple data are being fetched and operated on. Further, the data bus may have

different size than the address bus. This allows the optimal bus widths of the data and

address buses for fast execution of the instruction. The examples of Harvard

architecture are MCS-51 from Intel corporation and PIC from Microchip.

Von Neumann Architecture

In Von Neumann architecture, program and data share the same memory space. Von

Neumann architecture allows storing or modifying the programs easily. However, the

code storage may not be optional and requires multiple fetches to form the instruction.

Program and data fetches are done using time division multiplexing which affect the

performance. The example of Von Neumann architecture is 68HC11 from Motorola.

An embedded system can be defined as a computing device that does a specific

focused job. Appliances such as the air-conditioner, VCD player, DVD player, printer,

fax machine, mobile phone etc. are example of embedded systems. Each of these

appliances will have a processor and special hardware to meet the specific requirement

of the application along with the embedded software that is executed by the processor

for meeting that specific requirement. The embedded software40

is also called firmware.

The desktop/laptop computer is a general-purpose computer. We can use it for a variety

of applications such as playing games, word processing, accounting, software

development and so on. In contrast, the software in the embedded systems are always

fixed. Some of special features are listed below

Embedded systems do a very specific task.

Embedded systems have limited resources that have particularly in the memory.

A specific job has to be completed within a specific time. In some embedded

systems is called real-time systems.

Embedded systems consume very low power. Many embedded systems have

been operating thorough a battery power.

Embedded systems are highly reliable.

Some of embedded systems operate in extreme environmental conditions such

as very high temperatures and humidity.

More embedded systems are addressed to the consumer market for example,

electronic toys, mobile phones, home appliances etc.

The embedded system market is one of the highest growing areas as these

systems are used in consumer electronics, office automation, industrial automation,

biomedical engineering, wireless communication, data communication,

telecommunication, transportation, military etc.

Areas of Embedded systems

1. Consumer appliances

At home we use a number of embedded systems, which include digital camera, digital

dairy, DVD player, electronic toys, microwave oven, remote controls for TV and air-

conditioner, VCD player, video game consoles, video recorders etc. Today’s high-tech

car has about 20 embedded systems for transmission control, engine spark control, air-

conditioning, navigation etc. Even wristwatches are now becoming embedded systems.

The palmtops are powerful embedded systems using which we can carry out many

general-purpose takes such as playing games and word processing.

2. Office automation

The office automation products using embedded systems are copying machine, fax

machine, key telephone, modem, printer, scanner etc.

3. Industrial automation

A lot of industries use embedded systems for process control. These include

pharmaceutical, cement, sugar, oil exploration, nuclear energy, electricity generation

and transmission. The embedded systems for industrial use are designed to carry out

specific tasks such as monitoring the temperature, pressure, humidity, voltage, current

etc., and then take appropriate action based on the monitored levels to control other

devices or to send information to a centralized monitoring station. In hazardous

industrial environment, where human presence has to be avoided, robots are used,

which are programmed to do specific jobs. The robots are now becoming very powerful

and carry out many interesting and complicated tasks such as hardware assembly.

4. Medical electronics

Almost all medical equipments in the hospital are an embedded system. These

equipments include diagnostic aids such as ECG, EEG, blood pressure measuring

devices, X-ray scanners; equipment used in blood analysis, radiation, colonoscopy,

endoscopy etc. Developments in medical electronics have paved way for more accurate

diagnosis of diseases.

5. Computer networking

Computer networking products such as bridges, routers, Integrated Services Digital

Networks (ISDN), Asynchronous Transfer Mode (ATM) and frame relay switches are

developed with embedded systems, which are implemented to the necessary data

communication protocols. A router interconnects two networks, which may be running

different protocol stacks. The router’s function is obtain the data packets from incoming

ports, analyze the packets and sends them towards the destination after doing necessary

protocol conversion. Most networking equipments, other than the end-systems (desktop

computers) we use to access the networks, are embedded systems.

6. Telecommunications

In the field of telecommunications, the embedded systems can be categorized as

subscriber terminals and network equipment. The subscriber terminals such as key

telephones, ISDN phones, terminal adapters, web cameras are embedded systems. The

network equipment includes multiplexer, multiple access systems, Packet Assemblers

Disassembers (PADs), satellite modems etc. IP phone, IP gateway, IP gatekeeper etc. are

the latest embedded systems that provide very low-cost voice communication over the

Internet.

7. Wireless technologies

Advantages in mobile communications are paving way for many interesting

applications using embedded systems. The mobile phone is one of the marvels of the

last decade of the 20th century. It is a very powerful embedded system that provides

voice communication while we are on the move. The personal Digital Assistants and the

palmtops can now be used to access multimedia services over the Internet. Mobile

communication infrastructure such as base station controllers, mobile switching centers

are powerful embedded systems.

8. Instrumentation

Testing, measurement and controlling are the fundamental requirements in all scientific

and engineering activities. The measuring equipment in laboratories are used to measure

the physical parameters such as weight, temperature, pressure, humidity, voltage,

current etc. The test equipments such as oscilloscope, spectrum analyzer, protocol

analyzer, radio communication test set etc. are developed with the embedded systems.

9. Security

Security of persons and information has been a major issue. We need to protect the

information, transmit and also store the data. Developing embedded systems for security

applications is one of the most profitable businesses nowadays. Security devices at

homes, offices, airports and authentication are developed using embedded systems.

Encryption devices are used to encrypt the data/voice being transmitted on

communication links such as telephone lines. Biometric systems using

fingerprintandface recognition are now being extensively used for user authentication in

banking applications as well as for access control in high security buildings.

10. Finance

Financial dealing through cash and cheques are now slowly paving way for transactions

using smart cards and ATM (Automatic Teller Machine) machines. Smart cards and

credit card have a small microcontroller and extra memory and also it interacts with the

smart card reader/ATM machine and acts as an electronic wallet. Smart card technology

has the capability of ushering in cashless society.

Recent trends in embedded systems

Most of the embedded software was written only in assembly language and hence

writing, debugging and maintaining the code were very different and time consuming.

With the availability of powerful processors and advanced development tools,

embedded software development is no longer ‘rocket science’.

(i) Processor

The growing importance of embedded systems can be gauged by the availability of

processors. Powerful 8-bit, 16-bit, 32-bit and 64-bit microprocessors and

microcontrollers are available to provide the different market segments. The clock speed

and the memory addressing capability of the processor are also increased. Very

powerful digital signal processors are also available for real-time analysis of audio and

video signal.

(ii) Memory

The cost of memory chips is reducing day by day. As a result, the embedded systems

can be made functionally rich by incorporating additional features such as networking

protocols and even graphical user interface. The cost of memory chips used to

discourage developers from porting an operating system onto target hardware. As the

memory chips are becoming cheaper, porting an operating system is no longer an issue.

Now, wristwatches with embedded Linux operating system are available.

(iii) Operating system

A variety of operating systems are available which can be ported onto the embedded

system. The main advantage of embedding on operating system is that the software

development to be very fast, multitasking and maintaining the code is very easy. The

software can be developed in a high-level language such as C and C++. Linux operating

system is available as an open source in Internet. It is very useful to an embedded

systems and real time operating system applications. The complete source code is also

available for specific application. Just we can customize the software as per our

application needs.

(iv) Programming languages

Development of embedded systems software was mostly in assembly language.

However due to the availability of cross-compilers, most of the developers are done in

high level languages such as C and C++. The object-oriented languages like VC++, C++

and Java are catching up for more applications now. The main attraction of java

language is the platform independence. In fact, the development of java programming

languages was initiated mainly to address the embedded systems market.

(v) Development Tools

Availability of a number of tools for development, debugging and testing as well as for

modeling the embedded systems is now paving way for fast development of robust and

reliable systems. Development tools such as KEIL, RIDE, MATLAB and simulink can

be used to model embedded systems as well as to generate code, substantially reducing

the development time.

(vi) Programmable devices

Programmable logic device (PLDs) and field program beal gate arrays (FPGAs) pave

the way for reducing the components on embedded systems, leading to small, low-cost

systems. After developing the prototype of embedded systems, for mass production, the

FPGA can be developed which will have all the functionality of the processor,

peripherals as well as the application-specific circuitry. Systems-on-chip is the

catchword that reflects the current developments of programmable hardware in a single

chip embedded systems.

Applications

In our lives we come across many devices having a certain amount of intelligence

embedded systems that include automobiles, communications, military, medical,

consumer, entertainment appliances and personal digital assistances. In desktop

computers, we can find out more applications using microcontrollers such as keyboard,

modems, printers and other peripherals. In test equipment, microcontrollers make it

easy to add futures such as the display, store the data and display messages as well as

graphs. In consumer products the microcontrollers are essential inside of cameras, video

records, disk players and ovens. Embedded systems are playing a major role in

mentioned below fields

Analytical Instrumentation

Aeronautical Instrumentation

Bio-medical Instrumentation

Electronic Instrumentation

Industrial Instrumentation

Laser Instrumentation

Optical Instrumentation

Process Instrumentation etc.

Embedded system41

plays a pivotal role in instrumentation. The interfacing

of instruments with microcontroller has vastly increased our ability to measure and

compact in size. The attempt to design and develop of embedded based systems for the

measurement is rather scarce particularly in India though they offer many advantages.

Hence, the need to design and develop of embedded based system for measurement. In

the present study, an embedded based photoacoustic system is developed for the

measurement of air pollutants in industrial and automobile emissions.

Section 1.5

PURPOSE AND SCOPE OF THE PRESENT STUDY

Nowadays, air pollution is presented as a serious threat to the planet. The concentration

of gases from anthropogenic activities such as transport, cause consequences ranging

from local to global scale, effecting the climate, the environment and the human health.

It is necessary to detect and monitor of a large number of gas species emitted by these

source of pollutants. The photothermal techniques, specially photoacoustic

spectroscopy, allow the detection of many gaseous species. The estimation of air

pollutants such as nitrogen dioxide, carbon monoxide and carbon soot concentrations in

industrial and automobile emissions give valuable information to ecologists,

agriculturists, chemists, biochemists etc. The excess of these elements causes severe

health disorders in human beings, animals and plants. It is necessary to analyze these air

pollutants and to take necessary precautions. The measurements of concentration of

these pollutants are very essential to warn and educate the people on its toxic effects in

the corresponding fields.

Modern measuring instruments are the fruits of science and technology. New

discoveries in science provided new instruments for the study of nature and matter. The

precise and accurate measurement of physical and chemical parameters plays an

important role in unraveling the mysteries of nature.

No doubt, several investigators developed the techniques for the measurement of

air pollutants concentration in different samples and several manufacturers are

producing a variety of instruments for different pollutant estimation. But these are

conventional, indirect and suffer from many disadvantages. But the attempts to design

and develop the embedded based systems for the measurement of air pollutants are

rather scarce particularly in India though they offer many advantages. Hence, in the

present study, an attempt is made to design and development of embedded based

systems for measurement of air pollutants in industrial and automobile emissions.

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CHAPTER 2

Design and Development of Embedded

Based Photoacoustic Measurement

System - Hardware Design

Section 2.1

PRINCIPLE

In the present study, an embedded based photoacoustic system is designed and

developed. It works on the principle of photoacoustic effect1. The photoacoustic effect

is shown in Fig. 2.1. The embedded based photoacoustic system consists of a laser as

radiation source, a photoacoustic resonant cell as acoustic signal generator, acoustic

detector and the pollutant air whose pollutant concentration is to be estimated. The

photoacoustic cell2 generates the acoustic waves proportional to the concentration of the

air pollutant. The acoustic detector produces a voltage proportional to the acoustic

waves. The voltage produced is in the order of micro volts.

Different types of modulated laser sources are used as a exciting sources

corresponding to the air pollutant to be detected. These lasers offers high spectral

brightness and narrow spectral line widths. A square wave of function generator is used

to modulate the laser source at fixed frequency. The XR2206 is a function generator

chip. It acts as a square wave generator which is used to modulate the laser as well as

reference to the lock-in amplifier. The lock-in amplifier is a narrow bandpass filter and

amplifier which is used to measure very low level signal of about nano-volt (nV)

amplitude obscured by noise.

The voltage produced in the acoustic detector is given to a low noise

preamplifier of lock-in amplifier and the output of the lock-in amplifier in converted

into digital form with the help of an analog to digital converter. The embedded system is

used to acquire, process

and display the digital information corresponding to the air pollutant concentration with

appropriate interfacing devices. The necessary software to operate the system is

developed in embedded C language.

Section 2.2

FUNCTIOINAL BLOCK DIAGRAM

The functional block diagram of embedded based photoacoustic system for the

measurement of air pollutants is shown in Fig. 2.2. The block diagram consists of the

following different functional modules and sub-modules.

4. Radiation source

5. Modulator for radiation source

6. Photoacoustic cell

7. Acoustic detector

8. Low noise Pre-amplifier

9. Lock-in amplifier

10. Temperature sensing unit

11. Pressure sensing unit

12. Data acquisition system

13. ARM 32-bit microcontroller

14. LCD display

15. Power supply unit

16. Sample handling system

Each individual functional module is designed and implemented in the present study.

The details are presented in this chapter.

Section 2.3

RADIATION SOURCE

The two categories of radiation sources are used for photoacoustic studies3. The first

category has broad wavelength radiation sources such as arc lamps, halogen tungsten,

filaments, glowbar sources etc. which have low spectral brightness, incapability of fast

modulation and necessitate the use of external selective elements like prism or grating to

get tunable wavelength output. The second category has narrow wavelength radiation

sources such as lasers or monochromatic light sources. The advantages of laser sources

are high spectral brightness, narrow spectral line widths and intra or extra cavity

modulation. The different lasers such as solid state lasers, gas lasers and dye lasers are

developed and which are available in the market for scientific studies.

In present study, diode pumped solid-state (DPSS) lasers SDL-532, SLD-870

and SLD-1600 are used for the detection of nitrogen oxides, carbon soot and carbon

monoxide pollutants in industrial and automobile emissions. The lasers are obtained

from Dream lasers technologies limited, China. The diode pumped solid-state lasers are

solid state lasers which are made by pumping a solid gain medium with a diode laser.

They offer compactness, efficiency over other types and high power. The specifications

of DPSS laser sources are shown in Table 2.1(a), Table 2.1(b) and Table 2.1(c).

Table 2.1(a): Technical specifications of diode pumped solid state laser SDL-532

Table 2.1(b) : Technical specifications of diode pumped solid state laser SDL-870

S. No Parameter Value

1 Wavelength 870nm±1

2 Output power 20Mw

3 Operation mode CW

4 Modulation (TTL/Analog) frequency

range

0-5kHz

5 Operating temperature 5-50o C

6 Expect life time 10000 hours

S. No Parameter Value

1 Wavelength 532nm±1

2 Output power 20mW

3 Operation mode CW

4 Be Beam diameter 2mm

5 Beam roundness >95%

6 Modulation (TTL/Analog) frequency

range

0-5kHz

7 Operating temperature 5-50o C

Table 2.1(c) : Technical specifications of diode pumped solid state laser SDL-1600

S. No Parameter Value

1 Wavelength 1600nm±5

2 Output power 10mW

3 Operation mode CW

4 Modulation (TTL/Analog) frequency

range

0-5kHz

5 Operating temperature 5-50o C

6 Expect life time 10000 hours

Section 2.4

MODUALTOR FOR RADIATION SOURCE

It is necessary to modulate the laser beam for photoacoustic measurements. The various

techniques are used to modulate the laser sources which are described in detail in this

section. The suitable technique for modulation is essential to modulate the laser

accurately. The modulating techniques such as Q-switching, pulsating flash lamp,

frequency modulation, amplitude modulation, electro-optic modulation and mechanical

modulation have been used in photoacoustic studies. In those techniques, the amplitude

modulation technique is the most popular and suitable technique to use in present study.

The amplitude modulation techniques are commonly used in two ways which are briefly

described as follows.

(i) Mechanical amplitude modulation

Mechanical amplitude modulation is one of the techniques used in photoacoustic

measurement system which is generally called as mechanical chopper. The mechanical

chopper consists of a slotted disk and DC motor which places in the path of light beam.

It chops the light beam in form of 50% duty cycle. The chopper offers 100% modulation

within a range of frequency from few Hz to 500Hz only. The disadvantage of the

mechanical chopper is mechanical vibrations take place at higher frequencies (kHz) and

sound noise associate with the fast rotating blades.

(ii) Electronic amplitude modulation

The electronic amplitude modulation is one of the simple modulating techniques. It

operates a range of frequency from few Hz to MHz. The signal of function generator is

used to modulate the laser source in the present study. The function generator is a signal

generator which is used to modulate the laser source. The XR-2206 is a monolithic

function generator which produces high quality sine, square, triangle, ramp and pulse

waveforms. The output waveforms have high stability and good accuracy. The function

generator XR-2206 operates a range of frequency from 0.01Hz to 1MHz. The frequency

of operation can be selected by simple external resistor and capacitor. The salient

features of XR-2206 function generator are as follows

4. Sine wave distortion typically 0.5%

5. Temperature stability 20ppm/°C

6. Linear amplitude modulation

7. TTL Compatibility

8. Wide supply range

9. Adjustable duty cycle from 1% to 99%

The frequency of oscillator (Fo) of function generator is determined by the external

timing capacitor C and resistor R. The capacitor is connected across pin 5 & 6 and the

timing resistor is connected across pin 7&8 of function generator XR 2206 which are

shown in the circuit diagram. The output signal frequency of function generator XR

2206 is calculated as follows

Frequency, Fo = 1/ RC Hz

= 1/ 4.87K x 0.1µF

= 2.053 kHz

The signal frequency of function generator can be adjusted by varying a variable

resistor. The circuit diagram of square wave generator is shown in the Fig. 2.3. The

generated square wave of function generator XR22064 is used to modulate the diode

pumped solid state (DPSS) laser source. The modulated laser beam is applied to

generate the photoacoustic signal in the present study.

Section 2.5

PHOTOACOUSTIC CELL

The photoacoustic (PA) cell5 serves as a container for the sample. It is the heart of

photoacoustic spectrometer which is carefully designed and fabricated in present study.

The design of the PA cell depends on the nature of sample to be studied. A typical PA

cell should have the following characteristics

Proper acoustic shielding is required from ambient atmosphere.

Minimized unwanted signals due to interaction of the excitation light with cell

walls, windows and acoustic detectors or microphones.

Properly configured and placement microphones, sample inlet and outlet.

Increase the signal to noise ratio.

Two types of photoacoustic cells are used in photoacoustic studies which are as

follows

1. Resonant photoacoustic cell

2. Non-resonant photoacoustic cell

Resonant photoacoustic cell

The resonant photoacoustic cell is used to enhance the photoacoustic signal and signal

to noise ratio. The resonant6 frequency depends both on the shape of the resonator and

velocity of sound of the gas sample. The advantages of resonant photoacoustic cell are

simple to increase PA signal and eliminate unwanted signals. The different types of

acoustic resonant cells are shown in Fig. 2.4.

Table 2.2 : Types of acoustic resonators

S. No Name of acoustic resonator Mode of operation

1 Simple pipe Longitudinal

2 Pipe with two buffer volumes Longitudinal

3 Helmholz resonator Longitudinal

4 Coaxial resonator Radial

The acoustic noise creates a major problem in single cavity acoustic resonant

cell. The single cavity resonator is not sufficient to suppress the spurious noise. For this

reason, a differential or dual cavity7 (dual pipe with buffers) acoustic resonant cell is

designed and constructed in present study which can suppress back ground noise, flow

fluctuations and gives a relatively noise free photoacoustic signal. The differential

photoacoustic resonant cell is shown in Fig. 2.4(a) & 2.4(b). It consists of two copper

tubes, microphones, acoustic buffers and optical windows. The inner surface of copper

tubes polished and gold plated which can reduce the absorption of incident laser beam

and also withstand corrosion samples. The miniature microphones are sealed in PVC

holders and mounted centrally onto the sides of each tube which are well isolated

acoustically from the surroundings. The copper tubes are placed centrally in a aluminum

enclosure which has 120mm of length and 10mm of wall thickness. Each of the copper

tubes opens into a bigger acoustic buffer such as 50mm of length and 60mm of diameter

on either side. The volume of acoustic buffer is much larger than the cavities. The

acoustic buffers are used to reduce the window absorption noise, detector noise and

turbulence flow of a gas. The acoustic buffers consist of inlet port and outlet port. The

needle valve is used in the inlet line for controlling the flow of inlet gas sample. The

optical windows (BK7) are fixed to the both sides of acoustic buffers which are good in

quality and transmission of light. The dimensions of glass windows are 12.5mm of

diameter and 3mm of thickness which allow the wavelengths of visible region such as

380nm to 800nm. The glass windows are fixed with silicon ‘O’ rings and sealed tightly.

The enclosure of the resonant cell is made-up of aluminum material. The resonant cell is

mounted on a chassis which has a size of 500mm in length, 300mm in

width and 4mm in thickness which is shown in Fig.2.4(c). Finally, the resonant cell is

tested at its resonant frequency.

Characteristics of the photoacoustic resonant cell

The photoacoustic resonant cell characteristics are quite important in photoacoustic

measurements which depend on its acoustic resonant mode. The characteristics of the

photoacoustic resonant cell are enhancement of the PA signal, noise suppression and

increases signal to noise ratio, which are necessary to study the response of PA resonant

cell. Photoacoustic resonant cell is operated in longitudinal mode in present study.

In longitudinal mode8, the resonant frequency depends on the length and inner

diameter of copper tube, density and viscosity of the gas sample. The acoustic resonant

characteristics of the PA resonant cell are determined with air sample at atmospheric

pressure. A simple loud speaker kept close to one of the windows of the PA resonant cell

and the frequency is applied to the loud speaker from function generator, which is tuned

within a range of frequency from 100 to 4000Hz. The acoustic detector obtained the

signal and normalized against the amplitude of the audio signal being applied. The

fundamental and the first harmonic of the resonant frequencies are clearly seen with the

slight variations induced by the influence of other aspects such as buffer volume and

resonator cavity in the PA cell. Sub-resonant frequencies are shown before the

fundamental resonant frequency, but they are weaker than fundamental resonant

frequency.

Construction and working

A differential photoacoustic resonator is designed and constructed for the measurement9

of air pollutants in the present study. A differential acoustic resonator is a proper

solution of background noise, windows noise and flow fluctuations which contains two

acoustic resonators, one is signal sensitive resonator and another is reference resonator.

The signal sensitive resonator detects the actual acoustic signal and reference resonator

detects the photoacoustic background signal, windows noise and flow fluctuations. The

two longitudinal resonator tubes are placed in parallel and near to each other. The

resonator tubes are made of copper and polished with gold coating. They contain

excellent heat-conducting properties that absorb heat quickly and disperse in the copper

tube. The gold coating has been served not only to optimize the reflection of laser

radiation, but also to obtain a noncorrosive surface to withstand aggressive gases. The

two miniature professional microphones are equipped in acoustic resonators. An end of

acoustic resonators are opened and coupled with acoustic buffers. The acoustic buffers

are made of stainless steel which can withstand with corrosive gases which minimize

the acoustic noises such as background noise and inlet/outlet flow fluctuations.

Table 2.3 : Specifications of differential photoacoustic resonant cell

S. No Name of Parameter Designed value

1 Resonator length 80mm

2 Resonator diameter 5mm

3 Buffer length 50mm

4 Buffer diameter 60mm

5 Resonant frequency 2085 Hz

6 Quality factor 21 + 0.5

The resonant frequency and quality factor of acoustic resonator are expressed as

Resonant frequency, Fres = NC / 2(L+∆l) -------- (1), N= 1,2,3,4,5…

= 340 / 2(0.08+0.0015)

= 2085 Hz at 20 deg C

Quality factor (Q) = Fres / ∆f = ~ 21 -------- (2)

Where C is the velocity of sound in air, N is the acoustic longitudinal modes in

cylindrical resonator, L is the length of the resonant tube, ∆∆∆∆l is an end correction factor

and ∆∆∆∆f is the full width half maximum of resonant frequency. The theoretical resonator

frequency can be calculated as per equation (1) and expressed, but practical resonant

frequency is found at 2055Hz. A small variation is occurred due to made up of small

holes on resonators for acoustic detectors. The resonant frequency of photoacoustic

resonant cell is tested with a loud speaker which is explained in detail in chapter 4.

Section 2.6

ACOUSTIC DETECTOR

Acoustic detector or microphone is a transducer which is used to convert acoustic wave

into an electrical signal. The microphones use capacitance change to produce an

electrical voltage from mechanical vibration. The diaphragm of microphone acts as one

plate of a capacitor and the vibrations produce changes in the distance between the

plates. The constant DC voltage is applied to the microphone plates that the plates are

biased with a fixed charge (Q). The voltage (V) maintains across the capacitor plates

changes with the vibrations in the air according to the capacitance. The charging

capacity is given as

C = Q/V

Where Q is charge in coulombs, C is capacitance in farads and V is potential difference

in volts. The capacitance of the plates is inversely proportional to the distance between

them for a parallel-plate capacitor.

The input impedance of microphone is very high at audio frequencies and its

output is low thus it needs to interface high input impedance. Microphone is usually a

FET based buffer which is built in the microphone capsule. It acts as an impedance

transformer typical the output impedance is in order of few ohms. The sensitivity of the

microphone is typically 17mV/Pa and the frequency response is flat from less than 100

Hz to 10 kHz within 3dB which is an ideal detector for photoacoustic detection system.

The acoustic detector is shown in Fig.2.5. The specifications of the microphone are

shown in Table 2.4

Table 2.4 Specifications of Acoustic (Microphone) detector

S. No Parameter Value

1 Supply voltage range 0.9 to 1.6VDC

2 Current drain @ 1.3VDC 24mA typical, 50mA maximum

3 Frequency response/sensitivity 100 to 10 kHz

4 Sensitivity 10dB/Pascal

5 Sensitivity tolerance ± 3dB @ 1kHz

6 Dynamic output impedance 4.4 ohms typical

7 DC Output voltage Range 0.2 to 0.7VDC

8 Input-referred self-noise level 27dB typical, 30dB maximum

9 Output self-noise -100dBV maximum

Section 2.7

LOW NOISE PREAMPLIFIER

Normally acoustic detector produces very low voltage in the range of nano-volts to

micro volts. To measure such voltage from the acoustic detector, an ordinary

amplifier cannot be used. Hence, a low noise instrumentation amplifier INA 163 is

used which offers very low noise, low distortion, wide bandwidth, high input

impedance and dynamic response over a wide range of gain. It is ideal for low-level

audio signals of balanced low-impedance acoustic detectors or microphones.

The instrumentation amplifier INA 16310

amplifies the acoustic signal from micro

volts to few volts without noise. INA 163 maintains very low input bias current and

precise input characteristics over its full input common-mode voltage range. It offers

a very low drift of ±10µV/oC and high open loop gain of 100dB. The INA 163 is

unique in distortion cancellation circuitry and also reduces distortion in extremely

low level signals even at high gain. The INA 163 provides near to theoretical noise

performance at source impedance 200Ω and a simple external resistor sets the gain

up to 2000. The differential inputs of instrumentation amplifier provide superior

performance in professional microphone applications. The INA163 operates wide

supply voltage +4.5 to +18V, an excellent output voltage swing and drives high

output current. The outstanding performance characteristics of INA 163 allow its use

in the most critical instrumentation applications.

GAIN-SET RESISTOR

A simple single resistor is used to set the required gain of instrumentation amplifier

INA 163. The INA 163 has two internal 3k ohm feedback resistors with laser-

trimmed. The gain of amplifier is calculated as follows

Gain, G =1+6000/ RG

where RG is a gain resistor. An external gain resistor is used to adjust the gain up to

2000. The low noise instrumentation amplifier circuit is shown in the Fig. 2.6.

Section 2.8

LOCK-IN AMPLIFIER

For several applications lock-in amplifier requires the measurement of very low level

signal of about nano-volt (nV) amplitude obscured by noise. To achieve this task a lock-

in amplifier is normally used. The lock-in amplifier for embedded based photoacoustic

system is designed and implemented in the present study. It is a type of amplifier and a

narrow bandpass filter which can extract the signal from extremely noise environment.

Lock-in amplifier eliminates the noise even bandwidth is less than 0.1Hz and provide

the quality factor more than 103. It can amplify up to 180 dB. Lock-in amplifier11 is

used to measure the amplitude and phase of acoustic signal.

The lock-in amplifier consists of input amplifier, bandpass filter, phase locked

loop (PLL), phase sensing detector (PSD), low pass filter and output amplifier. The

block diagram of the lock-in amplifier is shown in Fig.2.7. The input amplifier amplifies

the acoustic signal from micro volts to milli volts and applies to the phase sensing

detector through a bandpass filter. The PLL uses the square wave of function generator

as the reference signal and it applies to the phase sensing detector through the phase

shifter. The phase shifter is employed to define a zero phase. The output of phase locked

loop consists of precise square wave and in-phase to the reference frequency. The PSD

output produces the result of phase difference and amplitude of the acoustic signal. The

sub-modules of lock-in amplifier are described.

Low offset operational amplifier

Operational amplifier OPA 177 is a low noise and high input impedance amplifier. It

offers very low offset voltage 25µV, low drift voltage 0.3µV/deg C and good accuracy.

The high performance makes ideally suited to precision instrumentation. The low

quiescent current of the OPA177 dramatically reduces warm-up drift and errors due to

thermoelectric effects in input interconnections.

The low offset operation amplifier12 OPA177 is used to amply the output signal

of phase sensing detector. The OPA177 is employed in the configuration of non-

inverting amplifier. The output voltage of OPA177 is calculated by the following

equation.

Vout = 1+R2/R1 x Vin

Where R2 is feedback resistance, R1 is input resistance and Vin is input voltage of

OPA117.

Bandpass filter

The bandpass filter of lock-in amplifier is employed to pass the frequencies within

certain range and rejects the frequencies outside of the range. The two types of bandpass

filters are generally used such as Active bandpass filter and passive bandpass filter. The

active bandpass filter requires an external power supply to make the use of active

components such as transistors or integrated circuits. The external source is not required

to make use of passive components such as capacitors, resistors and inductors etc. The

active bandpass filter is used to implement the lock-in amplifier in the present study.

The bandpass filter circuit is shown in Fig. 2.8.

The integrated circuit MAX 749013 is a universal switched capacitor filter,

which is used to design a band pass filter in the present study. It offers low power, low

operating voltage, Rail-to-Rail and wide dynamic range. The two clocking options are

available in the MAX9490, one is self-clocking and another is external clocking for

tighter cutoff frequency control. The ratio of clock to center frequency is 100:1. The

maximum center frequency of bandpass filter is 40kHz. MAX9490 operates a single

power supply which is available in SOP package of 16 pins. The center frequency of the

bandpass filter is calculated as follows.

Fo = fclk/100

= 205300/100

= 2053 Hz

Phase-Locked Loop

The modulating signal of the laser source is to be controlled. Hence the need to use the

phase -locked loop (PLL). In the present study, the phase-locked loop (PLL) HC7046 of

Texas instruments is used. The PLL HC7046 is a closed-loop frequency control system

based on the phase difference between the input clock signal and the feedback clock

signal of a controlled oscillator. The HC704614 offers excellent frequency linearity, high

speed,

wide range of operating voltage. The HC7046 consist of a voltage controlled oscillator

(VCO), comparator and low pass filter. The phase-locked loop circuit diagram is shown

in Fig. 2.9.

The phase comparator of PLL HC 7046 compares two input signal phases and

produces an error signal which is proportional to their phase difference. The error signal

controls the phase of voltage controlled oscillator15

. The VCO produces a negative

feedback if the output phase is drift, the error signal will increase and drive the VCO

phase in the opposite direction so as to reduce the error. Thus the output phase of VCO

is locked to other input phase. The capture frequency of VCO is calculated as follows

VCO frequency, Fosc = M (VCO/R) / 2C Vramp

= 6.2 (2.5/34.2k) / 2x600pf x 1.8

= 209.82k Hz

where M is multiplication factor and Vramp is ramp voltage.

Phase Sensitive Detector

Phase sensitive detector (PSD) is the heart of the lock-in amplifier. To measure the

phase difference of acoustic signal and reference signal, the need to use the phase

sensing detector16 A precision phase sensing detector AD630 in demodulator

configuration is used in present study. The AD630 consists of comparators, amplifiers

and laser trimmed capacitors. It offers wide bandwidth, low offset voltage and high

precision. The AD630 operates within a range of voltage from 5 to 16 volts. High slew

rate and fast settling time allow accurate signal processing in pulse conversion

applications.

The reference signal of laser source and acoustic signal through PLL and

bandpass filter17

are given to phase sensing detector AD 630. The phase sensing detector

processes these signals and produces DC voltage through a low-pass filter which is

proportional to the amplitude of acoustic signal18

and phase difference of inputs signals.

If these input signals are 90o out of phase, the output voltage of AD630 will be zero.

The low frequency noises of AD630 are removed by low-pass filter. The AD630 circuit

is designed and developed in present study which is shown in Fig. 2.10.

Section 2.9

TEMPERATURE SENSING UNIT

In order to measure the temperature in photoacoustic gas cell, the temperature is to be

sensed and measured. This unit consists of a temperature sensor LM3519

and the

associated circuitry which is shown in Fig. 2.11. The LM35 is a precision integrated-

circuit temperature sensor whose output voltage is linearly proportional to the

centigrade temperature. The LM35 does not require any external calibration or trimming

to provide typical accuracies of ±.0.5 °C at room temperature and ±1°C over a

temperature range from −40 to +120°C. The circuit has a dynamic impedance of less

than 1 ohm and operates within a range of current from 100 µA to 5mA. The LM35 has

a very low self-heating 0.08°C in the air. It operates linearly over a temperature range of

−40 to +120°C. The output of the LM 35 is calculated as follows.

Vo= 10mV / OC

The temperature measurement unit is designed and constructed. The circuit is

tested for different temperature measurements The results are presented in Table 2.5.

Table 2.5 : Temperature measurements

S. No. Temperature in

Thermometer ( oC)

Temperature in the

present system (oC)

Temperature in milli

volts

1 4.0 4.0 40.20

2 6.0 6.0 60.10

3 8.0 8.0 80.00

4 10.5 10.5 105.00

5 12.2 12.2 122.01

6 14.5 14.5 145.20

7 16.0 16.0 160.00

8 18.0 18.0 180.00

9 20.5 20.5 205.01

10 25.2 25.2 252.10

11 30.0 30.0 300.10

12 35.0 35.0 353.10

13 40.0 40.0 400.10

14 50.0 50.0 500.10

15 60.0 60.5 605.10

16 70.0 70.0 700.15

17 80.0 80.0 800.30

Section 2.10

PRESSURE SENSING UNIT

In order to maintain the sufficient pressure in photoacoustic gas cell, the pressure is to

be sensed and measured. This unit consists of a pressure sensor MPXV505020

and the

associated circuitry which is shown in Fig. 2.12. The MPXV5050 is a precision

integrated silicon pressure sensor which consists of on-chip temperature compensation

and calibration. In the present study, the MPX5050 pressure sensor is used to measure

the pressure of gas sample in photoacoustic cell.

The single element of pressure sensor combines advanced micro machining,

thin-film materialization and bipolar processing to provide an accurate and high-level

analog signal. The output voltage of pressure sensor is directly proportional to the

applied pressure. The MPXV5050 operates within a range of voltage from 4.75 to

5.25V. Unlike other sensors, the MPX5050 have a linear output. It operates linearly over

a pressure range of 0Kpa to 50Kpa.

The pressure measuring unit is designed and constructed. The circuit is tested for

different pressure measurements. The results are tabulated in Table 2.7

Table 2.6 : Specifications of pressure sensor MPX5050

S. No Parameter Value Unit

1 Pressure range 0 to 50 kPa

2 Supply current 7 mA

3 Pressure offset voltage 0.2 Volt

4 Full scale span @ 0-85 deg C 4.5 Volt

5 Accuracy @ 0-85 deg C 2.5 %V

6 Response time 1 mS

7 Offset stability +0.5 Vfss

Table 2.7 : Performance of pressure sensor

S. No Input pressure

(kPa)

Corresponding output

(Volts)

1 0 0.20

2 5 0.45

3 10 0.90

4 15 1.35

5 20 1.80

6 25 2.25

7 30 2.70

8 35 3.15

9 40 3.60

10 45 4.05

11 50 4.50

Section 2.11

ANALOG TO DIGITAL CONVERTER

The analog voltage corresponding to the air pollutant is converted into digital signal that

the microcontroller can understand. The analog to digital converter (ADC) is a device

that transforms data in the form of continuous analog variable into a discrete binary

code suitable for digital processing and is the core of any data acquisition system. In the

present study, 16-bit analog to digital converter AD7655 is used.

The Analog devices corporation AD7655 is a precision analog to digital

converter and combines successive approximation conversion. It operates a single 5V

power supply. It offers 16-bit resolution, dual channel, low noise, wide bandwidth,

simultaneous sampling, high-speed, internal conversion clock, error correction and both

serial and parallel ports. The track-and-hold of ADC has a 4-channel multiplexer and

one control input (A0). The control input A0 allows the simultaneously sampling of

input pairs INA1/INB1 (A0=low) or INA2/INB2 (A0=high). AD7655 operates within a

range of temperature from -25°C to 85°C. The features of analog to digital converter

AD7655 are as the follows

• Built-in track-and-hold amplifiers.

• 1 MSPS of Sampling Speed.

• Wide range of analog input voltage from 0 V to 5 V.

• No pipeline delay.

• SPI / QSPI / MICROWIRE / DSP compatible

• Power dissipation less than 5 mW

The component values are selected for optimum performance of the ADC for full-scale

voltage as recommended by the manufacturer’s data sheet which will result in a

resolution of 0.07mV/LSB.

Interfacing of ADC 7655 analog to digital converter wit

microcontroller

The Interfacing circuit of analog to digital converter AD7655 is shown in Fig. 2.13. The

output of the ADC AD7655 is in digital data form on pin D0 to D15, which is the

corresponding voltage of analog input. The digital data is placed on port pins of ARM

microcontroller. The D0 is the most significant bit and D15 is the least significant bit of

the ADC. The control pins of ADC converter are serial or parallel (SEP/PAR), end of

conversion (EOC), busy bit (BUSY), chip selection (CS), read (RD), channel selection

(A/B) and byte swapping (BYTESWAP) used to control the ADC while the conversion

of analog to digital data. In this present study, the ADC AD7655 is used in parallel

mode to get the digital output simultaneously and interfaced with the ARM

Microcontroller. The clock for ADC of frequency 24 MHz is derived from the external

crystal.

The detailed program, developed in C language on these lines, finds as a

subroutine in the main program which is presented in software development sections.

The performance of the analog to digital converter is tested and the results are shown in

Table 2.8.

Table 2.8 : Performance of data acquisition system

S.No. Input Voltage

(Volt)

Corresponding ADC Output

(Volt)

1 0.00 0.000

2 0.25 0.250

3 0.50 0.500

4 0.75 0.750

5 1.00 0.999

6 1.50 1.500

7 2.00 2.099

8 2.50 2.498

Section 2.12

ARM MICROCONTROLLER UNIT

The role of ARM microcontroller unit in the present study is to perform the following

tasks

• To measure the voltage of acoustic detector.

• To measure inside temperature of the photoacoustic cell.

• To measure inside pressure of photoacoustic cell.

• To process the measurement data.

• To display the measured data on LCD display.

The general purpose I/O lines P0.16 - P0.31 of microcontroller are used to data

lines D0-D16 of ADC for measurement of air pollutants, temperature and pressure. The

control lines of ADC such as Data channel selection (A0), Multiplexer selection (A/B),

Serial/Parallel selection (SER/PAR), Parallel mode selection (BYTESWAP), Busy bit

(BUSY), End Of Conversion (EOC), Read Data (RD) and Chip Select (CS) are used to

control the conversion of analog to digital converter by microcontroller. To display the

measurement data, the LCD display is interfaced with microcontroller. The data lines

D0-D7 and control lines P.28-P.30 (RS, R/W and EN) of LCD display and port lines of

P0.20-P.27 of microcontroller are used for measurement data of air pollutants,

temperature and pressure, the microcontroller. The LCD display is interfaced with

microcontroller through a latch 74HC573. For these tasks we used LPC2106

microcontroller which is shown in Fig.2.14.

The ARM Microcontroller is a 32-bit RISC22

processor architecture which is

developed by ARM Limited that widely used in embedded systems nowadays. The

power saving features of ARM CPU is dominant in where the critical design goals of

low power consumption. Today, the ARM family accounts for approximately 90% of all

embedded 32-bit RISC CPUs. The LPC210623

is a 32-bit Microcontroller,

ARM7TDMI-S CPU with real-time emulation. The 128-bit wide memory interface and

a unique accelerator architecture enable 32-bit code execution at maximum clock rate.

For critical code size applications, the alternative 16-bit Thumb mode reduces code by

more than 30 % with minimal performance penalty. Due to their tiny size and low

power consumption, this microcontroller is ideal for embedded applications where

miniaturization is a key requirement such as measurements, access control and point-of-

sale. The PWM channels and 32 GPIO lines make this microcontroller particularly

suitable for industrial control, analytical and medical systems. The salient features of

LPC microcontroller are as follows

32-bit ARM7TDMI-S processor.

64 KB on-chip Static RAM.

128 KB on-chip Flash Program Memory.

128 bit wide interface/accelerator.

Enables high speed 60 MHz operation.

In-System Programming (ISP) and In-Application Programming (IAP) via on-

chip boot-loader software.

Vectored Interrupt Controller with configurable priorities and vector addresses.

Multiple serial interfaces including two UARTs, Fast I2C and SPI.

Two 32-bit timers, PWM unit (6 outputs), Real Time Clock and Watchdog timer.

32 general purpose I/O pins in a tiny LQFP48 package.

On-chip crystal oscillator with an operating range of 1 MHz to 30 MHz.

Processor wake-up from Power-down mode via external interrupt.

Individual enable/disable of peripheral functions for power optimization.

Dual power supply: CPU operating voltage range of 1.65 V to 1.95 V.

I/O power supplies range of 3.0 V to 3.6 V with 5 V tolerant I/O pads.

Section 2.13

LIQUID CRYSTAL DISPLAY

In the present study, the LCD display FDCC200424 is used for displaying the measured

air pollutant, temperature and pressure of the emission gas. The display is a 5x8 dot

matrix liquid crystal display that display alphanumeric, character and special symbols. It

is a 20 characters and 4 line LCD display unit. The LCD consists of in-built controller

and driver that provide connectivity between a dot matrix LCD and microcontroller. The

LCD FDCC2004 is manufactured by Fordata Electronic Corporation Pvt. Limited,

China. The features of the LCD display FDCC2004 are as follows

5x8 dots with cursor.

Easy interface with 8 –bit mode.

Built-in controller in LCD module.

Display data RAM contains 80 characters.

5 Volts power supply.

Low power Consumption.

High contrast and wide viewing angle.

The liquid crystal display is interfaced with the ARM Microcontroller LPC2106

in the present study. Microcontroller reads the data from each channel of analog to

digital converter and displays the data on LCD display. The concentration of air

pollutant is displayed on first line; the sample pressure in photoacoustic cell is displayed

on second line and the sample temperature is displayed on third line of LCD display.

The pin and interfacing detail of LCD with the microcontroller are given in Table 2.7

and Table 2.8.

Table 2.7 : Pin assignment of LCD display

Pin Symbol Function

1 Vss GND

2 Vdd Power supply

3 V0 Contrast Adjust

4 RS Register Select

5 R/W Data Read/Write

6 E Enable signal

7 – 14 D0 – D7 Data lines

15 LED + Power supply (+)

16 LED - Power supply (-)

Table 2.8 : Interfacing of Microcontroller with LCD display

Microcontroller

I/O pins

LCD display

P0.20 – P0.27 Data byte (D0 – D7)

P0. 28 Register selection (RS)

P0.29 Read/Write(R/W)

P0.30 Enable (E)

The 74HC57325 is a high-speed octal transparent latch. It is used as a line driver

between the microcontroller and LCD display. The input lines D0-D7, output enable OE

and output lines Q0 – Q7 of 74HC573 are used for LCD display. The interfacing of

LCD display with ARM microcontroller LPC 2106 is shown in Fig. 2.15. The pin

details of 74HC573 are given in Table 2.9.

Table 2.9 : Pin assignment of latch 74HC573

Pin Symbol Function

1 OE Output enable

2-9 D0 – D7 Data inputs

10 GND Ground

11 LE Latch enable

12 – 19 Q7 – Q0 Data outputs

20 VCC Supply

Section 2.14

POWER SUPPLY UNIT

The embedded based photoacoustic system requires the following D.C supply voltages

to operate the system.

± 5V/500 mA

± 12V/500 mA

The transformers with secondary ratings 15–0–15V/1A are selected to meet the required

specifications.

The circuit diagram of the power supply unit is shown in Fig.2.16. Three pin IC

regulators 7805 and 7905 are used to get the 5V and -5V power supply and 7812, 7912

for +12V and –12V power supplies. The diodes 1N4007 used for rectification and the

filter capacitors C1and C2 are 330µF/25V used to eliminate the fluctuations. The C3,

C4, C5 and C6 of 0.lµF are used to eliminate the high frequency components. The

power supplies designed in the present study gives required voltages within ± 0.01%

line and load regulation. The individual blocks of the present study are tested with the

power supply.

The hardware circuits of the present system are tested with the various gas

samples. The detailed schematic diagram of the embedded based measuring system is

shown in schematic diagram.

Section 2.15

SCHEMATIC DIAGRAM AND WORKING

The schematic diagram of design and development of embedded based photoacoustic

system is designed and implemented. The modulated laser source is used to generate the

acoustic signal in photoacoustic resonant cell. The Photoacoustic (PA) resonant cell is

specially designed and fabricated for gas analysis, which is used to generate an acoustic

signal in order of milli volts (amplitude) at 2055 Hz of frequency. Generated acoustic

signal is detected by professional microphone, which is connected to the PA cell. The

low noise pre-amplifier INA163 is used to amplify the signal of acoustic detector. The

output signal of pre-amplifier is used to bandpass (MAX7490) filter, which eliminates

the noise of low and high pass frequencies and allow specific bandwidth of frequency.

The output signal of bandpass filter is used as input to phase sensitive detector (PSD).

The function generator (XR2206) is constructed to generate the square wave

about 2055 Hz of frequency, which is used to laser source. The laser is electronically

modulated at given frequency, it is also used as a reference signal to the phase-locked

loop and the phase sensitive detector. The PA signal and reference signals are used to

the phase sensing detector (PSD). The PSD picks up only the signal from the noises,

which is the same frequency of the reference signal. The output signal of the PSD is

used to the channel 1 of Analog to digital converter through the gain operational

amplifier.

The output signal of temperature sensor LM35 is used to the channel 2 of

Analog to digital converter through operational amplifier OPA117. The output signal of

pressure

sensor MPX5050 is applied to the channel 3 of analog to digital converter through

operational amplifier OPA117. The analog to digital converter AD7655 contains 4

analog input channels, which are used to PA signal, temperature sensor and pressure

sensor. The output digital data of ADC is connected to the microcontroller LPC2106.

The microcontroller sends the data to the 4-line LCD display. The final data is displayed

line by line on 4-line LCD display. The schematic diagram and PCBs of the embedded

based photoacoustic system are shown in Figs. 2.17, 2.17(a), 2.17(b), 2.17(c), 2.17(d)

and 2.18.

Section 2.16

SAMPLE HANDLING UNIT

The sample handling unit is used to collect the gas samples from various industrial

emissions. It consists of a suction pump, connecting tubes, dust particle filter, buffer

tank and flow regulator. The inlet tube of suction pump21

is connected to stainless steel

pipe and outlet is connected to the input of buffer tank. The stainless steel pipe can

withstand at high temperatures. The buffer tank stores the gas sample and supplies to the

photoacoustic cell without flow fluctuations through a dust filter and air flow

regulator22

. The dust filter is used to collect the dust particles and allow very fine

particles to the photoacoustic cell through a flow regulator. The flow regulator

maintains a required flow rate about 1.5 Lt/min of gas sample. The photoacoustic cell

maintains the pressure up to 20 KPa of gas sample at room temperature.

After completion of the gas sampling process, the complete photoacoustic

system will be ready to measure the air pollutants in the industrial and automobile

emissions which is shown in Fig.2.19.

REFERENCES

1. C Haisch and R Niassner, Spectroscopy Europe, 14, 11 (2002).

2. Andra Miklo and Peter Hess, Review of Scientific Instruments, 72 (2001).

3. V Deepak Bageshwar, S Avinash Pawar and V Khanvilkar, Eurasian J. Anal.

Chem.,5, 187, (2010).

4. The datasheet of Function Generator XR2206 (www.bucek.name/pdf/xr2206.pdf).

5. J M Frans Harren, Gina Cotti, Jos Omens and Sacco Hekkert, “Photoacoustic

Spectroscopy in Trace Gas Monitoring”, John Wiley & Sons Ltd. (2006).

6. F J M Harres, F G C Bijnen, 30, 137, Netherlands (1990).

7. Frank Muller, Alexander Popp and Frank Kuhnemann, Optical Society of America,

11, 2820,Germany (2003).

8. A Tavakoli, M Taheri and H Saghafifar, “Design, Simulation and Structural

Optimization of a Longitudinal Acoustic Resonator for Trace Gas Detection using

Laser Photoacoustic Spectroscopy”, ICOP 2009-International Conference on Optics

and Photonics, India (2009).

9. Zoltan Bozoki, Janos Sneider, Zoltan Gingl and Gabor Szab, Measurement Science

Technology, 10, 999 (1999).

10. The Data sheet of Preamplifier INA163,

http://www.ti.com/lit/ds/symlink/ina163.pdf.

11. H Scofield John, American Journal of Physics, 62, 129 (1994).

12. The Datasheet of Low Noise Preamplifier

(http://www.ti.com/lit/ds/symlink/opa177.pdf).

13. Kerry Lacanette, “Basic Introduction to Filters—Active, Passive and Switched-

Capacitor”, National Semiconductor, Application note 779, (2010).

14. Garth Nash, “Phase-Locked Loop Design Fundamentals”, Freescale Semiconductor

Application note, Document number: AN535, Rev. 1.0, (2006).

15. The Datasheet of Phase Locked Loop (http://www.alldatasheet.com/datasheet-

pdf/pdf/ 15655/PHILIPS/74HC7046A.html).

16. G Bradley Armen, “Phase Sensitive Detection: The lock-in Amplifier”, Department

of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee

(2008).

17. Jim Karki, “Active Band-pass Filter Design”, Application Report, Texas

Instruments (2000).

18. Jimmy Ng and A H Kung, Optics Letters, 29, 1206, Taiwan (2004).

19. The Datasheet of Temperature Sensor (http://www.ti.com/lit/ds/symlink/lm35.pdf).

20. The datasheet of Calibrated Pressure Sensor, web link :

http://www.datasheetcatalog.org/ datasheet2/e/0z5dil0g15741p7huyq7xj1e8a3y.pdf.

21. Suction Pump, Model No. HS-WP-1, High Speed Appliances, Manufacture,

Mumbai,

India.

22. Flow Regulator, TRAC Model No. 35BO, Transducers and Controls Pvt. Limited,

Hyderabad, India.

CHAPTER 3

Design and Development of Embedded

Based Photoacoustic Measurement

System - Software Development

Section 3.1

SALIENT FEATURES OF EMBEDDED C LANGUAGE

The C language is a general-purpose computer programming language developed in

1972 by Dennis Ritchie at the Bell Laboratories. The C programming language is the

most popular programming language for programming desktop computers. The

embedded C language1 is a subset of C language. It is a popular programming

(1,2)

language for microcontroller based systems. The embedded C is growing in importance

for embedded systems and real-time operating system applications. Exactly as the PC is

the standard for personal computing, the ARM microcontroller is the standard for 32-bit

microcontroller. The concept of embedded C compiler3 for ARM microcontroller

executing on a PC is familiar now. Embedded C language is an inherent language,

flexibility and portability across a wide range of hardware. The specific reasons are

mentioned below for use of embedded C

Embedded C language is a programming language for microcontrollers.

It is developed for embedded system programming and also used for real

time application programming4.

Embedded C language is a mid-level with high-level features such as

support for functions and modules in embedded systems.

It is code flexibility, efficiency and ability to access specific hardware

via pointers.

Using embedded C library functions and header files ensure that application

source code can be recompiled for different microcontroller targets.

Well-established embedded C compilers are available for embedded systems

such as KEIL5 and RIDE compilers for 8-bit to 32-bit microcontrollers.

Embedded C language breadth of expression is brief and powerful.

Debugging and maintaining code written in embedded C is much easier than

code written in assembly language.

Characteristics of embedded C language

Embedded C is a language of functions, data types6, assignments and flow controls. To

program in embedded C, one must call a function and most functions return values. The

value returned from a function, the value of data variable or the value of constant could

be used in an assignment statement to change the value of another variable. With the

addition of flow is control if, while, for and do-while in embedded C.

Embedded C language contains a small set of data types: Signed and unsigned

integers, characters, floating point numbers7, characters, bit fields and enumerated

types. In embedded C, one can declare a pointer variable that points to any data type.

The address arithmetic of embedded C is sensitive to the properties of the pointer being

adjusted. Pointers to functions are also supported in embedded C. The data types can be

extended by building structures that are hierarchies of members, each member being

one of the data types or an earlier-declared structure. Arrays of data types can be

declared. An array consists of any data type, including a structure or union. Arrays can

have multiple dimensions.

Some of the important decision making statements, control instructions,

functions, arrays and pointers of embedded C language8 used in developing the present

project software are described as fellows

(a) if statement

if statement is available in embedded C. It is a powerful decision making statement and

used to control the flow of execution of statements. The general of if statement is as

follows

if (expression)

Statement -1

Statement -2

Statement -3

It is two-way statement. An expression is valid which executes the following statement-

1 and statement-2 otherwise expression is false control comes out from the loop and

executes the outside statement-3.

(b) while loop

The while loop evaluates the test expression before every loop, it can execute non-zero

times if the condition is initially true. The general form of while loop is shown as

follows

while (expression)

Statement

Example :

int x =1;

while (x<20)

Printf (“%d\t”, x);

x = x+1;

(c) for loop

The for loop in embedded C is the most general looping construct. The loop header

contains three parts such as initialization, continuation condition and action. The

general form of for loop is as shown below

for (initialization; continuation; action)

Statement

The initialization is executed once before the body of the loop is entered. The loop

continues to run as long as the continuation condition remains true. After every

execution of the loop, the action is executed.

The following example executes 10 times by counting 0 to 9. Many loops look very

much like the following

Example :

int i;

for (i = 0; i < 10; i ++)

printf (“%d \n”, i);

(d) Function

A function6 in embedded C language is a block of code or statements that performs a

specific task. It has a name and it is reusable i.e. it can be executed from as many

different parts in a embedded C program as required. It also optionally returns a value

to the calling program. Function has obtained some of special properties which are as

follows.

(i) Every function has a unique name. This name is used to call function from “main

()” function. A function can be called from within another function.

(ii) A function is independent and it can perform its task without intervention from or

interfering with other parts of the program.

(iii) A function performs a specific task. A task is a distinct job that your program must

perform as a part of its overall operation.

(iv) A function returns a value to the calling program.

Example :

address ();

printf(“\n SK University, Anantapur, India”);

address ()

printf (“ \n Dept. of Instrumentation");

(e) Array

An array in embedded C language is a collection of similar data-type. It can hold value

of a particular data type, which has been declared. Arrays can be created from any of

the embedded C data-types such as int, float and char. An integer array can only hold

integer values and cannot hold values other than integer. When we declare an array, it

allocates contiguous memory location for storing values whereas 2 or 3 variables of

same data-type can have random locations. It is the most important difference between a

variable and an array.

Syntax : data_type array_name[width];

Example:

int array[6];

int sum = 0; sum = array[0] + array[1];

printf (“\n%d”, sum);

(f) Pointer

A pointer6666 is a secondary data type also known as derived data type in

embedded CCCC. It is built from one of the primary data types available in

embedded C C C C language. Basically pointer contains memory address of other

variable or function as their value. As pointer deals with memory address, it can

be used to access and manipulate data stored in memory.

Benefits of pointer in embedded C program

Pointer is one of the most exciting features of embedded C language and it has added

power and flexibility to the language. Pointer offers following benefits to the

programmers

Pointers can handle arrays and data tables efficiently.

Pointers can support dynamic memory management.

Pointer helps to return multiple values from a function through function

argument.

Pointer increases program execution speed.

Pointer is an efficient tool for manipulating structures, linked lists, queues

stacks etc.

Syntax : data_type* pointer name;

Example:

int i=9,*ptr;

ptr=&i;

printf("Value of i : %d\n",i);

printf("Address of i : %u\n",&i);

printf("Address of ptr : %u\n",&ptr);

printf("Ptr pointing value :%d",*ptr);

getch();

The outputs are

9

65524

65520

9

KEIL embedded C CROSS COMPILER

Keil is a embedded C cross compiler which is used to translate high-level program to a

low-level language. It is a 32-bit integrated development environment9 which supports a

set of development tools for ARM 32-bit microcontroller10

applications. Keil was

founded in 1986. Keil developers have built up many years of experience to develop

embedded C cross-compilers. The development tools of Keil are a complete solution to

developing software for ARM 32-bit and 8051 8-bit families of microcontrollers. It can

be used to create a source file, compile, link and covert options with an easy to use user

interface. Keil cross compiler contains a real view compilation tool, micro vision IDE

and debugger(3,9)

.

In present work, embedded C language is chosen to develop the software for

embedded based photoacoustic system for measurement of air pollutants.

Section 3.2

SOFTWARE DEVELOPMENT

The software is developed in embedded C language using KEIL cross compiler for

measurement of air pollutants in automobile and industrial exhausts. The main role of

the software in the present study is to govern the following activities using ARM 32-bit

microcontroller.

17. To acquire the data from various detectors through the ADC such as acoustic

detector, temperature detector and pressure sensor.

18. To make the data acquisition system and convert the analog to digital data.

19. To compute and display of air pollutants, photoacoustic cell temperature and

pressure measurements.

20. To make the different functional units of system work in a systematic and

sequential manner.

21. The necessary software in the present study is developed in embedded C

language to implement these tasks for effective functioning of the system.

Software Routines

The software program developed in the present study is divided into five parts using the

functions in embedded C language. Each routine is described as follows.

1. Display the name of measurement on LCD routine

Initialization of microcontroller (General I/O Port, Pin direction, clock).

Send the command for register selection (RS).

Send the command for Read / Write (R/W).

Write the name of display on I/O port.

High the enable pin of LCD then Low.

Call delay.

2. Detection of air pollutant routine

Initialization of microcontroller (General I/O Port, Pin direction, clock).

Select the channel-1 of ADC.

Write the command for start of conversion of ADC.

Read the busy bit until it is low.

Equate the digital data to analog data.

Display the analog data on LCD display.

Call delay.

3. Measurement of Temperature routine

2 Initialization of microcontroller (General I/O Port, Pin direction, clock).

3 Select the channel-2 of ADC.

4 Write the command for start of conversion of ADC.

5 Read the busy bit until it is low.

6 Equate the digital data to analog data.

7 Display the analog data on LCD display.

8 Call delay.

4. Measurement of Pressure routine

Initialization of microcontroller (General I/O Port, Pin direction, clock).

Select the channel-3 of ADC.

Write the command for start of conversion of ADC.

Read the busy bit until it is low.

Equate the digital data to analog data.

Display the analog data on LCD display.

Call delay.

5. Simultaneous display of all parameters on LCD display routine

10. Initialization of microcontroller (General I/O Port, Pin direction, clock).

11. Display the name of instrument on first line.

12. Display the concentration of Air pollutant in ppm on second line.

13. Display the temperature in degree centigrade on third line.

14. Display the pressure in Kilo Pascal (KPa) on fourth line.

15. Display the analog data on LCD display.

16. Call delay.

The software program (hex code) is dumped into flash memory of LPC2106 by

using the Philips flash programmer11

through RS232 communication protocol12

. The

program is ready to execute in LPC2106 microcontroller for real time applications. The

detailed flow charts of software program of the present system is developed as follows

Fig. 3.1 : Flow chart diagram of embedded based photoacoustic system for

measurement of air pollutant

Clean & Purse the PA

gas cell

Inject the sample to the PA cell

Switch ON the measurement

system

Run the software to measure

the air pollutant

Start

Select channel 1

Read ADC output corresponding to the

air pollutant concentration

Compute and display on LCD

Fig. 3.2: Flow Chart diagram for Temperature and Pressure measurement

Select channel-2

from ADC

Read ADC output corresponding

to the existing temperature

Compute the temperature

value

Display in degree

centigrade on LCD

Start

Select channel- 3

from ADC

Read ADC output corresponding

to the existing pressure

Compute and the display of the

pressure value on LCD

Section 3.3

PROGRAM IN DETAIL

The software is developed for the measurement of air pollutants such as nitrogen

dioxide, carbon soot and aerosols. The temperature and pressure of the gas sample in

PA cell are also measured simultaneously. In present study, the program is developed in

embedded C language using KEIL C cross compiler. The program in detail is given

below.

Program Details

***** Program for the measurement of air pollutants *****

-------------------------------------Header files -------------------------------------------------

#include<stdio.h>

#include<LPC210X.H>

#include<stdlib.h>

------------------------------------- Definitions --------------------------------------------------

#defineLCD_INIT 0X38 //LCD initialization

#defineDispOn_CursorBlink 0x0C

#defineClrDisplay 0x01

#defineCursrRightShift 0x06

#define rs 0x10000000 // Register selection

#define rw 0x20000000 // Read/Write

#define en 0x40000000 //Enable

#define Latch 0x80000000

#define Clear 0xFFF00000 // Clear controller port pins

#define busy 0x08000000 // Busy bit of ADC

#define RESOL 0.000076 //76 µV resolution-16bit adc

------------------------------------- Functions --------------------------------------------------

void clk_int(void);

void lcd_int(void);

void lcd_string(char *senpoint);

//void lcd_string1(char *senpoint1);

//void lcd_string1();

void lcd_line1(void);

void lcd_line2(void);

void lcd_line3(void);

//void lcd_line4(void);

void DataSend();

void DataSend1();

void DataSend2();

void lcd_display();

void lcd_display1();

void lcd_display2();

void lcd_display3();

void lcd_display4();

void lcd_line1_m(void);

void lcd_line2_m(void);

void lcd_line3_m(void);

void lcd_line4_m(void);

void delay_ms();

void delay_us();

void lcd_cmd(unsigned int letter);

void lcd_char(unsigned int letter);

//void lcd_char1();

void lcd_busy(void);

void cmdwrt(void);

void datawrt(void);

-----------------------------------Initialization -----------------------------------------------------

unsigned char OUTPUT1[5];

float Gfltfs_temp;

unsigned int Ddata;

int DIGITAL_DATA1,DIGITAL_DATA2;

----------------------------------Delay function ----------------------------------------------------

void delay_ms(int x)

int a,b;

for(a=0;a<x;a++)

for(b=0;b<3500;b++);

---------------------------------LCD command writes function ----------------------------------

void cmdwrt()

IOSET = Latch;

IOCLR =rs;

delay_ms(5);

IOCLR =rw;

delay_ms(5);

IOSET =en;

delay_ms(20);

IOCLR =en;

delay_ms(5);

-------------------------------- LCD command initialization function ---------------------------

void lcd_cmd (unsigned int letter)

IOCLR = 0x0FF00000;

IOSET = Latch;

Ddata =(letter<<20 );

Ddata=Ddata & 0xFFF00000;

//lcd_busy();

IOCLR = en;

IOSET =Ddata;

IOCLR = ~ Ddata;

delay_ms(5);

cmdwrt();

----------------------------------LCD data write function -----------------------------------------

void datawrt()

IOSET = Latch;

IOSET =rs;

// delay_ms(5);

IOCLR =rw;

// delay_ms(5);

IOSET =en;

delay_ms(10);

IOCLR =en;

// delay_ms(5);

------------------------------ LCD Character display ------------------------------------------

void lcd_char(unsigned int letter)

//delay_ms(5);

IOSET = Latch;

IOCLR = 0x0FF00000;

Ddata =(letter<<20);

Ddata=Ddata & 0xFFF00000;

IOSET =Ddata;

IOCLR = ~ Ddata;

//delay_ms(5);

datawrt();

//delay_ms(5);

----------------------------------------- LCD string display ----------------------------------------

void lcd_string (char *senpoint)

while (*senpoint != '\0')

lcd_char(*senpoint);

//delay_ms(5);

senpoint++;

--------------------------------------- ADC Conversion -------------------------------------------

floatToString(float Gfltfs_temp)

Gfltfs_temp = Gfltfs_temp;

OUTPUT1[0] = Gfltfs_temp /1000 + '0';

Gfltfs_temp = (int)Gfltfs_temp % 1000;

OUTPUT1[1] = Gfltfs_temp /100 + '0';

Gfltfs_temp = (int) Gfltfs_temp % 100;

OUTPUT1[2] = Gfltfs_temp /10+ '0';

Gfltfs_temp = (int)Gfltfs_temp % 10;

OUTPUT1[3] = Gfltfs_temp + '0';

OUTPUT1[4] = '\0';

-------------------------------------- Line Address commd ------------------------

void lcd_line3_m(void)

lcd_cmd(0x9f);

void lcd_line2_m(void)

lcd_cmd(0xca);

void lcd_line1_m(void)

lcd_cmd(0x88);

/---------------------------LCD line 4 Initialization -------------------------------/

void lcd_line4(void)

lcd_cmd(0xd4);

//delay_ms(5);

/---------------------------LCD line 3 Initialization--------------------------------/

void lcd_line3(void)

lcd_cmd(0x94);

//delay_ms(5);

/---------------------------LCD line 2 Initialization----------------------------------/

void lcd_line2(void)

lcd_cmd(0xc0);

//delay_ms(5);

/----------------------------LCD line 1 Initialization------------------------------------/

void lcd_line1(void)

lcd_cmd(0x80);

//delay_ms(5);

/------------------------------------------LCD display 1 function------------------------/

void lcd_display1(void)

// lcd_line1();

lcd_cmd(0x80);

//delay_ms(5);

lcd_string(" PA GAS ANALYZER ");

//delay_ms(5);

//lcd_line2();

lcd_cmd(0xc0);

//delay_ms(5);

lcd_string("PA Signal-");

//delay_ms(5);

/-----------------------------------------LCD display function------------------------------/

void lcd_display2(void)

lcd_line3();

//lcd_cmd(0x99);

//delay_ms(5);

lcd_string("Concent -");

//delay_ms(5);

lcd_line4();

//lcd_cmd(0xd6);

//delay_ms(5);

lcd_string("Tempertr -");

//delay_ms(5);

/-------------- Concentration of Air pollutant display function------------/

void lcd_display3(void)

delay_ms(5);

lcd_cmd(0xCB);

//delay_ms(2);

DIGITAL_DATA1=IOPIN;

Gfltfs_temp=(float)RESOL* DIGITAL_DATA1*1000;

floatToString(Gfltfs_temp);

lcd_string(OUTPUT1);

lcd_string(" mV ");

lcd_cmd(0x9F);

floatToString(Gfltfs_temp/1.2);

lcd_string(OUTPUT1);

lcd_string(" PPM ");

/----------------------------------Temperature display function--------------------/

void lcd_display4(void)

delay_ms(5);

lcd_cmd(0xDF);

DIGITAL_DATA2=0X0e65;

Gfltfs_temp=(float)RESOL*DIGITAL_DATA2/10 *1000;

floatToString(Gfltfs_temp);

lcd_string(OUTPUT1);

lcd_string(" oC ");

/-------------------------------------------LCD display function---------------------------/

void lcd_display(void)

lcd_display1();

lcd_display2();

while (1)

lcd_display3();

lcd_display4();

//lcd_cmd(0x01);

/---------------------------------------LCD Initialization-------------------------------------/

void lcd_int(void)

lcd_cmd(LCD_INIT); //set 8-bit mode and 2 lines

lcd_cmd(LCD_INIT);

lcd_cmd(DispOn_CursorBlink); //display on - cursor blink on

lcd_cmd(ClrDisplay); //clear display

lcd_cmd(CursrRightShift); //cursor move & shift right

delay_ms(5);

/----------------------------LCD clock Initialization ---------------------/

void clk_int(void)

PLLCON =0x00; // Disenable and disconnect the PLL

delay_ms(5);

PLLFEED=0xAA;

delay_ms(5);

PLLFEED=0x55;

delay_ms(5);

/------------------------------------Main program start------------------------------------/

int main(void)

delay_ms(300);

clk_int();

PINSEL0 = 0x00000000;

PINSEL1 = 0x00000000;

IODIR = 0xFFFFFFFF;

IOCLR = 0xFFFFFFFF;

IOSET = Latch;

lcd_int();

while(1)

lcd_display();

/---------------------------------------Program end -------------------------------------------/

Section 3.4

CALIBRATION AND MEASUREMENT PROCEDURE

The individual blocks of the embedded based photoacoustic system for the

measurement of air pollutants are designed and constructed. The necessary software is

developed in embedded C language. The software details are already discussed. Before

using the photoacoustic system for real samples, the system must be calibrated by

measuring a series of known standard gas samples. In the present study, the system is

calibrated using the standard samples obtained from Chemtron Science Laboratories

Pvt. Limited, Mumbai, INDIA. Initially the software program of photoacoustic system

is run for calibration. After the execution of the program, the photoacoustic system

measurements are displayed on LCD display as shown below

(vi) Air pollutant concentration measurement.

(vii) Temperature measurement.

(viii) Pressure measurement.

The measurement procedures are also needed to consider in advance of making any

measurements. The measurement procedures of photoacoustic system are mentioned as

follows.

Clean the Photoacoustic (PA) resonance cell and keep it dry.

Connect the PA cell and Laser source to the electronic circuit.

Close inlet and outlet valves of PA cell tightly.

Purge the PA cell with nitrogen gas.

Switch ON the system and activate the software.

Switch ON the laser source in electronic modulation mode.

Fill the sample gas into PA cell according to the required pressure.

The system measures and displays the concentration of the sample along

with pressure and temperature.

Repeat the steps from 4 to 8.

Note the readings of the air pollutants concentration along the temperature and

pressure.

REFERENCES

1 S Michel Pont, “Programming Embedded Systems”, Addison Wesley

Publications, University of Leicester (2003).

2 E Balaguruswamy, “Programming in ANSI C” 2nd

Edition, TATA McGraw Hill

Publishing Company Limited, New Delhi (1998).

3 The User Manual, C cross Compiler, V7.2, Altium Publishers (2006).

4 K V K Prasad, “Embedded/Real-Time Systems”, Dream Tech Publishers, India

(2009).

5 The Keil Cross Compiler, ARM Company (Website: www.keil.com).

6 Yashavant Kanethkar, “Let Us C”, 5th Edition, BPB Publications, New Delhi

(2003).

7 The Training Manual of Chltenham Training Program, Gloucestershine, UK

(1998).

8 Brian W Kernighan, “The C Programming Language”, 2nd

Edition, AT&T Bell

Laboratories, Murray Hill, New Jersy (1998).

9 The Integrated Development Environment, ARM Company

(Website:www.keil.com/arm/asp).

10 IC LPC2106 32-bit Microcontroller, Datasheet, Philips Electronics, USA (2004).

11 Flash Programmer, "LPC2000 Flash Utility", Version 2.1, Philips

Semiconductors, USA (2003).

12 IC MAX232 Driver/Receiver, Datasheet, Maxim Integrated Products,

Sunnyvale, CA (1999).

CHAPTER 4

Standardization of Embedded based

Photoacoustic Measurement System

Section 4.1

INTRODUCTION TO STANDARDIZATION

The embedded based photoacoustic system for the measurement of air pollutants in

automobile and industrial emissions is designed and constructed in the present study.

The various concentrations of calibrated nitrogen dioxide samples are used to

standardize the embedded based photoacoustic measurement system.

For standardization1

of the photoacoustic measurement system, a diode pumped

solid-state laser source SDL-532 is used as a light source which is the maximum single

frequency and output of 20mW centered at 532nm wavelength. A square wave generator

is used to modulate(2,3)

the laser source at fixed frequency which is specially designed by

XR2206 Integrated circuit. The same modulating frequency is used to the lock-in

amplifier as a reference signal. The photoacoustic resonant cell4 is used to generate the

acoustic signal5 which is detected by microphone. The acoustic signal is applied to the

pre-amplifier6. An amplified signal is given to the lock-in amplifier. The lock-in

amplifier is specially designed to eliminate the noise in photoacoustic detection system.

The lock-in amplifier output is used to the analog to digital converter which is converted

analog signal into digital data. The digital data is applied to the microcontroller. The

microcontroller is used to process the data and display the resultant data on LCD

display. The standard NO2 samples are used to standardize the developed photoacoustic

measurement system.

Section 4.2

RESPONSE OF THE PHOTOACOUSTIC RESONANT CELL

The frequency response7 of photoacoustic resonant cell is required to study before the

standardization of the photoacoustic measurement system. In present study, the acoustic

resonant characteristics are determined with the air sample. The air sample is injected

into photoacoustic resonant cell which is tested with a simple loudspeaker at room

temperature. The loudspeaker is kept very close to one of the windows place of the

photoacoustic resonant cell. The signal of frequency 100Hz to 4000Hz is applied to the

loudspeaker from a function generator in steps of 100 Hz. The audio signal response is

obtained from the microphone detectors in photoacoustic resonant cell. The response of

the PA cell is plotted in the graph against applied frequency of loudspeaker. The

resonant frequency is clearly seen with very slight variation induced by the influence of

other aspects like buffer volume, inlet port, outlet port and microphone holes which tend

to distort the resonance profile.

The resonant frequency characteristics of photoacoustic resonant cell are studied

using a simple loudspeaker. The maximum resonant frequency is obtained at 2055 Hz of

speaker frequency which is shown in Fig. 4.1.

Table 4.1 : Frequency response of photoacoustic resonant cell using a loudspeaker

S. No

Frequency (kHz)

PA amplitude (Volts)

1 0.10 0.152

2 0.20 0.176

3 0.30 0.176

4 0.40 0.176

5 0.50 0.184

6 0.60 0.184

7 0.66 0.250

8 0.70 0.192

9 0.80 0.192

10 0.90 0.200

11 1.00 0.200

12 1.10 0.224

13 1.20 0.224

14 1.30 0.236

15 1.40 0.248

16 1.50 0.262

17 1.60 0.263

18 1.70 0.265

19 1.85 0.360

20 1.90 0.550

21 1.95 0.860

22 2.00 1.100

23 2.05 1.180

24 2.10 0.700

25 2.30 0.320

26 3.00 0.240

27 4.00 0.180

Section 4.3

STANDARDIZATION OF THE SYSTEM WITH NITROGEN DIOXIDES

Standard nitrogen dioxide (NO2) gas samples of various concentrations such as 10ppm,

100ppm, 500ppm and 1000ppm obtained from Chemtron Science Laboratory, Mumbai,

India are used for standardization. The experimental setup for measurement of standard

samples is shown in Fig. 4.2.

Measurement Procedure

22. Clean the Photoacoustic resonant cell and keep it dry.

23. Connect the PA cell detectors to the electronic circuit.

24. Select TTL modulation mode of laser source8.

25. Switch ON the hardware system and activate the software.

26. Switch ON the laser source and align the beam to resonant cell.

27. Purge the PA cell with nitrogen gas.

28. Fill the sample gas into PA cell according to the required pressure.

29. Close inlet and outlet valves of PA cell tightly.

30. The system detects, measures and displays9 the gas concentration along with

temperature10

and pressure.

31. Repeat the steps from 6 to 9.

32. Note the readings and draw the graph of PA amplitude as a function of sample

concentration.

The various concentrations of nitrogen dioxide are tested and results are shown in Figs.

4.4 to 4.7. The PA signal behavior is qualitatively in good agreement with the standard

gas samples.

Section 4.4

STANDARDIZATION OF EMBEDDED BASED PHOTOACOUSTIC

SYSTEM - RESULTS AND DISCUSSION

In the present study, various standard concentrations of nitrogen dioxide are chosen for

the standardization of an embedded based photoacoustic measurement system. The

standard NO2 samples - 10 ppm, 100 ppm, 500 ppm and 1000ppm are collected from

Chemtron Science Laboratory, Mumbai, India. The concentration of nitrogen oxides of

these standands are measured with the designed and developed in present study. The

results of the measurements are presented in Table 4. 8. These measurements are also

made with the Standard Gas Analyzer, Model No.T200H used in Ramky Laboratory,

Hyderabad. The results are presented in the same table for comparison. The individual

results of measurements of standard gases are also presented in Tables 4.4 to 4.7 and

Figs. 4.4 to 4.7.

The baseline of the system is also tested with the nitrogen sample which has

almost stable baseline throughout the range of modulating frequencies. The baseline

profile is shown in the Fig. 4.3. All samples are tested at constant pressure 20kPa and at

room temperature10

. The system is quite successful in the measurement of nitrogen

dioxide in the given standard samples with an accuracy of ±1ppm.

Table 4.3 : Baseline measurement of nitrogen sample

S. No

Frequency (kHz)

PA amplitude (mV)

1 0.20 0.36

2 0.30 0.40

3 0.40 0.42

4 0.50 0.40

5 0.60 0.44

6 0.66 0.52

7 0.70 0.39

8 0.80 0.40

9 0.90 0.40

10 1.00 0.39

11 1.10 0.40

12 1.20 0.42

13 1.30 0.41

14 1.40 0.42

15 1.50 0.40

16 1.60 0.41

17 1.70 0.43

18 1.80 0.46

19 1.90 0.50

20 2.00 0.60

21 2.05 0.70

22 2.10 0.66

23 2.50 0.43

24 3.00 0.40

25 4.00 0.39

Table 4.4 : Measurement of standard NO2 (10ppm)

S. No

Frequency

(kHz)

PA Amplitude

(Volts)

1 0.10 0.0030

2 0.20 0.0030

3 0.30 0.0040

4 0.40 0.0050

5 0.50 0.0040

6 0.66 0.0055

7 0.70 0.0050

8 0.80 0.0040

9 0.90 0.0040

10 1.00 0.0040

11 1.50 0.0040

12 1.60 0.0040

13 1.70 0.0040

14 1.80 0.0040

15 1.90 0.0040

16 1.95 0.0070

17 2.00 0.0130

18 2.05 0.0170

19 2.10 0.0140

20 2.20 0.0050

21 2.50 0.0040

22 3.00 0.0040

23 4.00 0.0040

Table 4.5 : Measurement of standard nitrogen dioxide (100 ppm)

S. No Frequency

(kHz)

PA amplitude

(Volts)

1 0.10 0.012

2 0.20 0.012

3 0.30 0.012

4 0.40 0.015

5 0.50 0.013

6 0.66 0.029

7 0.60 0.016

8 0.70 0.012

9 0.80 0.015

10 0.90 0.014

11 1.00 0.010

12 1.60 0.012

13 1.70 0.014

14 1.80 0.015

15 1.90 0.020

16 1.95 0.024

17 2.00 0.050

18 2.02 0.112

19 2.05 0.182

20 2.08 0.110

21 2.10 0.034

22 2.30 0.020

23 2.50 0.019

24 3.00 0.013

25 4.00 0.014

26 5.00 0.013

Table 4.6 : Measurement of standard nitrogen dioxide (500ppm)

S. No Frequency (kHz) PA amplitude (Volts)

1 0.10 0.06

2 0.20 0.06

3 0.30 0.06

4 0.40 0.07

5 0.50 0.08

6 0.66 0.10

7 0.60 0.08

8 0.70 0.06

9 0.80 0.08

10 0.90 0.07

11 1.00 0.05

12 1.60 0.06

13 1.70 0.07

14 1.80 0.08

15 1.90 0.10

16 1.95 0.12

17 2.00 0.25

18 2.02 0.56

19 2.05 0.86

20 2.08 0.60

21 2.10 0.17

22 2.30 0.10

23 2.50 0.09

24 3.00 0.09

25 4.00 0.07

Table 4.7 : Measurement of standard nitrogen dioxide (1000ppm)

S. No Frequency (kHz) PA amplitude (Volts)

1 0.10 0.121

2 0.20 0.121

3 0.30 0.128

4 0.40 0.152

5 0.50 0.136

6 0.66 0.296

7 0.60 0.163

8 0.70 0.128

9 0.80 0.156

10 0.90 0.144

11 1.00 0.104

12 1.60 0.128

13 1.70 0.144

14 1.80 0.152

15 1.90 0.200

16 1.95 0.248

17 2.00 0.502

18 2.02 1.120

19 2.05 1.720

20 2.06 1.000

21 2.10 0.340

22 2.50 0.200

23 3.00 0.196

24 4.00 0.136

25 5.00 0.144

Table 4.8 : Measurement of NO2 samples at various concentrations

*Gas Analyzer Model No. T200H, Teledyne, Instruments, CA, USA.

S. No

Input standard

NO2 concentration

(ppm)

Present study

Standard Gas

Analyzer*

(ppm)

Corresponding

output

(Volts)

1 10 9.80 9.85 0.017

2 100 98.50 99.20 0.182

3 250 247.00 248.40 0.450

4 500 496.00 498.00 0.870

5 750 745.50 747.00 1.320

6 1000 989.00 993.50 1.720

REFERENCES

17. K M Adams, Applied Optics, 27, 4052 (1988).

18. Frank Muller, Alexander Popp and Frank Kuhnemann, Optical Society of

America, 11, 2820 (2003).

19. C Haisch and R Niassner, Spectroscopy Europe, 14, 11 (2002).

20. Andra Miklo´s and Peter Hess, Review of Scientific Instruments, 72, 1937

(2001).

21. Frans Harren, Gina Cotti, Jos Omens and Sacco Hekkert, “Photoacoustic

Spectroscopy in Trace Gas Monitoring”, John Wiley & Sons Publishers (2006).

22. IC INA163 Low Noise Preamplifier, Datasheet, Texas instruments company,

Texas (2005).

23. Harren, Bijnen and Reuss, Applied physics, 50, 137, Netherlands (1990).

24. DPSS Laser (SDL-532-020), Shanghai Dream Lasers Technologies Co., Ltd,

China.

25. LCD module (FDCC2004), Datasheet, FORDATA Electronic corporation

Limited, China.

26. IC LM35 Precision Centigrade Temperature Sensor, Datasheet, National

Semiconductors (2000).

CHAPTER 5

Measurement of Nitrogen Oxides in

Industrial Emissions

Section 5.1

INDUSTRIAL EMISSIONS

India is one of the ten most industrialized nations of the world. But this status

has risk of accidents. Industrial emissions are rapidly increasing in India. These

pollutants are usually harmful to the health of human beings, animals, plants and

environment. brought with it unwanted and unanticipated consequences such as

unplanned, industrialization, urbanization, air pollution1 and the risk of accidents.

Industrial emission are rapidly increasing in india.

Seven categories of industries in Andhra Pradesh such as pharma industries,

cement plants, thermal power plants, oil refineries, petrochemicals, integrated iron and

steel plants, pesticides and fertilizer units are identified as significant air polluting

industries. These industries are distributed in Hyderabad, Ranga Reddy, Medak and

Visakhapatnam areas. The list of industries in Hyderabad, Ranga Reddy district area is

given in Table 5.1. The pharma sector has the maximum number of industries followed

by thermal plants, cement and fertilizer plants. It indicates that pharma-based and

process industries have major shares of 45% and 32% of the total number of industries

respectively.

Table 5.1 : List of industries in Hyderabad and Ranga Reddy districts

S. No. Name of industry Type of industry District

1 Mylan Pharma Pharmaceutical Ranga Reddy

2 Aurobindo Pharma Limited Pharmaceutical Hyderabad

3 Zenotech Labs Ltd. Pharmaceutical Hyderabad

4 Dr. Reddy’s Laboratory Pharmaceutical Hyderabad

5 Divis Laboratory Ltd. Pharmaceutical Hyderabad

6 SMS pharmaceutical Pharmaceutical Hyderabad

7 Gulf oil corporation Process Ranga Reddy

8 Natco Pharma Pharmaceutical Hyderabad

9 Matrix Laboratory Ltd. Pharmaceutical Ranga Reddy

10 Aptuit Laurus Ltd. Pharmaceutical Hyderabad

11 Hyderabad rubber products Rubber plant Hyderabad

12 Genix Pharma Ltd. Pharmaceutical Hyderabad

13 Gland pharma Ltd Pharmaceutical Ranga Reddy

14 Glochem industries Pharmaceutical Hyderabad

15 Hetero drug Ltd. Pharmaceutical Ranga Reddy

16 Neuland Laboratories Ltd. Pharmaceutical Hyderabad

17 SH Pharma Ltd. Pharmaceutical Hyderabad

18 Agri-lifie Fertilizer plant Ranga Reddy

19 Erythro Pharma Pvt. Ltd. Pharmaceutical Hyderabad

20 Indian Genomix Pvt. Ltd. Pharmaceutical Hyderabad

21 Joflo industries Pharmaceutical Ranga Reddy

22 Ravoos Laboratory Ltd. Pharmaceutical Ranga Reddy

23 Saraca Laboratories Ltd. Pharmaceutical Hyderabad

24 Thermax industries Power plant Ranga Reddy

25 Vamshi rubber Limited Rubber plant Hyderabad

26 ATS GeneTech Pvt.Ltd. Pharmaceutical Hyderabad

27 Co-Gen power plant Power plant Hyderabad

28 Likhitha industries Process plant Hyderabad

29 Rastria chemical & fertilizer Ltd. Chemical plant Ranga Reddy

30 RCC Lab. India Ltd. Pharmaceutical Hyderabad

31 Suven Life Sciences Ltd. Pharmaceutical Hyderabad

32 Pains industries Process Ranga Reddy

33 Hyderabad Chemical

Products Ltd.

Chemical plant Ranga Reddy

34 Nayagara Industries Ltd. Process plant Ranga Reddy

35 Poly Hi Solidur Plastics

India Ltd.

Plastic plant Ranga Reddy

The following are the major air pollutants of these industrial emissions.

• Nitrogen oxides

• Carbon soot

• Carbon monoxide

• Sulphur dioxides

• Carbon dioxide

• Volatile organic components etc.

Section 5.2

NITROGEN OXIDES POLLUTANT

Nitrogen oxides (NOx) are a mixer of nitric oxide (NO) and nitrogen dioxide (NO2). It

is one of the most prominent air pollutants and a poison by inhalation. NOx is a reddish-

brown, pungent and acidic gas which is strongly corrosive. The combustion of fuel such

as coal, gasoline and oil engines produces NOx pollutant. NOx is generating usually

from reaction of nitrogen and oxygen atoms during combustion process at high

temperatures. The oxygen and nitrogen do not react at ambient temperatures, but they

can react at high temperatures and produce various oxides of nitrogen into atmosphere

which are as follows.

N2 + O2 → 2NO

2O2 + N2 → 2 NO2

In most of the cities, the industries and motor vehicles contribute high amount of

nitrogen oxides in the atmosphere. The industries and motor vehicles such as thermal

power plants, pharmaceutical industries, rubber industries, diesel engine generators,

diesel motor vehicles etc. are contributing about 80% of ambient nitrogen dioxides in

the city environment. Nitrogen dioxide is also produced from the industrial processes of

nitric acid, metals, welding, refining of petrol and explosives. The main source of

nitrogen oxides is the result of industrial activities2. The emissions of nitrogen oxides

(3-

5) from various fuels used in the industries are presented in the Table 5.1.

Table 5.2: Emission levels of nitrogen oxides from various fuels

S. No Name of Fuel

Emission of NOx

(g/kg fuel)

1 Oil 3.0

2 Kerosene 3.0

3 Coal 4.5

4 Propane 2.3

5 Gasoline 27.0

6 Natural Gas 1.0

7 Butane 2.3

8 Wood 0.7

Effects on health

The NOx is a poison by inhalation. The long-term exposure to NOx at concentrations

above 100µg/m³ causes adverse health effects. Nitrogen dioxide irritates the lungs and

lower resistance to respiratory infections6 such as flu and grippe. The effects of short-

term exposure are still unclear, but continued exposure to concentrations is typically

much higher than those normally found in the ambient air. Children are more sensitive

to the effects of nitrogen oxides. The health effects in children are as follows

• Short-term exposure to NOx concentrations (>3 ppm) can decrease lung

function.

• Frequent exposure to low concentrations (<3 ppm) can irritate lungs.

• Concentrations as low as 0.1 ppm cause lung irritation and measurable decreases

in lung function in asthmatics.

• Long-term exposures to lower level concentration can destroy lung tissue and

lead to emphysema.

Effect on the environment

Nitrogen oxides contribute to form ozone7 and can have adverse effects on both

terrestrial and aquatic ecosystems. Nitrogen oxides in the air can significantly contribute

to anumber of environmental effects such as acid rain and biological process in coastal

waters. In biological process, the body of water suffers with nutrients. NOx leads to

reduce in the amount of oxygen in the water and environment which is destructive to

fish and other animal life.

Effects on visibility

Nitrogen oxides can form secondary particles which are called nitrates. It causes haze

and reduces visibility. Nitrogen oxides make summer smog which looks like brownish

in colour.

Thus the nitrogen oxides of these industrial emissions need to be monitored and the

measures to reduce them are to be initiated. Hence, in the present study, it is proposed to

measure the concentration of nitrogen oxides of the industrial emissions of

pharmaceutical and process industries of Hyderabad and Rangareddy districts in Andhra

Pradesh with the instrument developed in the present study.

Section 5.3

EXPERIMENTAL PROCEDURE

The following experimental procedure is followed in the measurement of nitrogen

oxides from the industrial emissions.

1. Clean the photoacoustic resonant cell and keep it dry.

2. Connect the PA cell detectors to the electronic circuit.

3. Select the laser source and use in modulation mode.

4. Switch ON the hardware system and activate the software.

5. Switch ON the laser source and align the beam to resonant cell.

6. Purge the PA cell with nitrogen gas.

7. Fill the standard gas sample gas into PA cell according to the required pressure.

8. Close inlet and outlet valves of PA cell tightly.

9. The measurement system measures and displays the gas concentration along

with temperature and pressure.

10. Repeat the steps from 6 to 9.

11. Note the readings of photoacoustic measurement system.

The experimental arrangement is already described in chapter 2.

Section 5.4

MEASUREMENT OF NITROGEN OXIDES OF INDUSTRIAL

EMISSIONS RESULTS AND DISCUSSION

The pharmaceutical and process industries of Hyderabad and Ranga Reddy districts as

indicated in Table 5.3 are chosen for the measurement of nitrogen oxides of the

industrial emissions. The samples are collected from these industries. The concentration

of nitrogen oxides8 of these industrial emissions are measured with the system designed

and developed in the present study. The results of the measurements are presented in

Table 5.4. These measurements are also made with the Standard Gas Analyzer, Model

No.T200H used in Ramky Laboratory, Hyderabad. The results are presented in the same

Table for comparison. The results of the present study are in good agreement with those

values obtained from the standard gas analyzer. The range of these measurements is

1ppm to 1000ppm with the deviation error of ±1%.

The industrial emission samples from Aurobindo pharma, Dr. Reddy’s pharma

and Hyderabad rubber plant have very high nitrogen oxide levels. The emission samples

from Thermax industries contain high concentration of nitrogen oxides. The emission

samples from Gulf oil corporation, Likhita industries, and Mylan pharma are having

moderate NOx and remaining three emission samples from Paint industry, Gland

pharma and Hetero drugs R&D are having below emission standards (120ppm for NOx)

of pollution control board.

Table 5.3 : List of selected industries for measurement of nitrogen oxides

S. No. Name of industry Type of industry Location

1 Mylan pharma limited Pharmaceutical Ranga Reddy

2 Aurobindo pharma industry Pharmaceutical Ranga Reddy

3 Hetero drugs plant Pharmaceutical Hyderabad

4 Gulf oil corporation Process Ranga Reddy

5 Co-gen power plant Process Hyderabad

6 Dr. Reddy’s laboratory Pharmaceutical Ranga Reddy

7 Likhita industries Process Hyderabad

8 Paints industry Process Ranga Reddy

9 Gland pharma Limited Pharmaceutical Ranga Reddy

10 Hyderabad rubber Plant Process Hyderabad

Table 5.4 : Measurement of nitrogen oxides of industrial emissions

S. No Name of industry,

Location

Sample

accumulated from

Present study

(ppm)

Standard Gas

Analyzer*(ppm)

1 Aurobindo Pharma

Industry,

Bachupally, Ranga

Reddy dist.

Reactor exhaust

754.5

756.2

2 Dr.Reddy’s

Laboratory,

Ranga Reddy dist.

Reactors exhaust

679.5

681.5

3 Hyderabad rubber

Plant, Hyderabad.

Exhaust pipe

629.0

630.2

4 Thermax industries,

Ranga Reddy dist.

Boiler chimney

606.7

608.4

5 Gulf oil corporation,

Hyderabad.

Boiler chimney

523.9

525.2

6 Likhita industries,

Hyderabad.

Exhaust pipe

516.5

518.4

7 Mylan pharma,

Ranga Reddy dist.

Exhaust pipe

469.0

470.3

8 Paints industry,

Ranga Reddy dist.

Chimney

314.8

315.2

9 Gland pharma,

Jeedimetla, Ranga

Reddy dist.

Chimney/ exhaust

117.2

118.1

10 Hetero drugs

plant(R&D)

Hyerabad.

Exhaust/chemney

97.6

99.7

*Gas Analyzer Model No.T200H, Teledyne Instruments, CA, USA

REFERENCES

1. Aaron Daly and Paolo Zannetti “An Introduction to Air Pollution- Definitions,

Classifications and History”, The EnviroComp Institute, Fremont, USA (2007).

2. Mark Jacobson, Journal of Geophysical Research, 115, 78 (2010).

3.Schramm, Sthel and Da Silva, Infrared Physics & Technology, 44, 263 (2003).

4.Nancy Marley and Jeffrey Gaffney,” New improved Fast GC-Luminol Instrument

for PAN and Nitrogen Dioxide Measurements”, Environmental Research Division

Argonne National Laboratory, Argonne, Illinois, USA(2001).

5. G J Wendel, DH Steadman, and C. A. Cantrell, Analytical Chemistry, 55, 937 (1983).

6. S Soehodh and S Taufic, Eastern Asia Society for Transportation Studies, 5,

1841 (2005).

7. A Yerramilli, V S Challa and V B R Dodla, “Simulation of Surface Ozone

Pollution in the Central Gulf Coast Region using WRF/Chem model: Sensitivity to

PBL and Land Surface Physics,” Advances in Meteorology, 2011 (2010).

8. T Brugman, “Laser Based Diagnostics on NO in a Diesel Engine”, Ph.D Thesis,

Nijmegen University (1999).

CHAPTER 6

Measurement of Carbon Soot Pollutant

in Automobile Emissions

Section 6.1

AUTOMOBILE EMISSIONS

One of the most concerning problems faced by the modern society is the atmospheric

pollution1, which can cause dangerous environmental consequences such as the

degeneration of air quality, acid rain, photochemical2 smog, ozone layer depletion,

health diseases and the global warming.

Several emission sources such as internal combustion engines of motor vehicles,

power plant boilers, hog-fuel boilers, central steam heat boilers, waste incineration,

local field burning, house fires, forest fires, fireplaces etc. generate huge of carbon

soon3 to the atmosphere which is the resultant of pyrolysis process. The exterior sources

such as smoking substances, oil lamps, candles, wood stoves, quartz/halogen bulbs with

settled dust, fireplaces and defective furnaces also contribute to the indoor environment.

The majority of carbon soot release from automobile emissions4 in cities. The carbon

soot forms in various size and shape during the normal combustion processes5 in diesel

engines. The rate of soot generation in automobile depends on many factors which are

as follows

• Engine type, size and configurations.

• Equipment applications, operating modes and frequencies.

• Fuel delivery and control settings.

• Intake and exhaust gas recirculation (EGR) conditions.

• Wear modes of the engine and fuel delivery components.

• Age of equipment.

The transport is liable for a great part of the damaging soot pollutant emitted by

anthropogenic sources. The greater municipality of Hyderabad located in Andhra

Pradesh has more than seven million inhabitants. Having a great fleet of motor vehicles,

it is summarily important to evaluate automobile emissions of gases harmful to planet

and human health.

About Hyderabad City

Hyderabad, a 400 year old city is the state capital of Andhra Pradesh. It lies on the

Deccan Plateau, 541 meters (1776 ft) above sea level, over an area of approximately

650 square kilometers. Hyderabad, along with its twin city of Secunderabad, is the fifth

largest city in India, with a population nearing 8 million. Due to its prominence as a

major high-tech center, it is one of the fastest growing with a population density of

~17,000 persons per square kilometer. The rapid rate of urbanization with increased

economic activity has encouraged migration to the twin cities, which led to an increase

of personal, public, and para (3 and 6 seat autos) transit vehicles, industrial output and

increasing burden on the cities infrastructure. Hyderabad along with the surrounding ten

municipalities constitutes the Hyderabad Urban Development Authority (HUDA) and

has been growing at an average rate of 9%. Air pollution is a growing health hazard in

the city. Among the many sources of pollution, the transport sector is contributing a

significant amount of carbon soot pollution.

Section 6.2

CARBON SOOT POLLUTANT

Carbon soot is one of the air pollutants. It is a general term that refers to impure carbon

particles resulting from the incomplete combustion of a hydrocarbon. Carbon soot is in

the general category of airborne particulate matter which is considered hazardous to the

lungs and general health, when the particles are less than five micrometers in diameter

such particles are not filtered out by the upper respiratory tract. Carbon soot emits from

various sources such as internal combustion engines, power plant boilers, central steam

heat boilers, waste incineration, local field burning, house fires, forest fires, furnaces

etc.

Characterization of carbon soot

During the last 20 years a large number of studies have allowed a better understanding

of carbon soot and its characterization(5,6)

. In spite of all these efforts a lot has still to be

learned about this unique filler. The mono unit of carbon soot is the aggregate, a sub-

micron object of complex shape. The images of carbon soot are shown in Fig.6.1 which

are taken by Transmission Electron Microscope (TEM) instrument. The type and size of

carbon soot particles7 are given in Table 6.1.

Table 6.1: Carbon soot particle type and sizes of various exhausts

S. No Carbon soot type Size range (nm) Source of

generation

1 Acetylene flame soot 5 to 50 Flame

2 Candle flame soot 10 to 100 Flame

3 Kerosene flame soot 20 to 600 Flame

4 Diesel exhaust soot 20 to 300 Diesel generator

5 Electric arc soot 20 to 300 Palas electric arc

6 Plastic burning soot 10 to 200 Plastic bag

7 Styrofoam burning soot 10 to 200 Styrofoam

8 Wood burning soot 30 to 300 White oak

9 Rice straw burning soot 30 to 600 Rice straw

Two kinds of soot particles are regulated by the Indian government. One is fine

soot particles (PM2.5) which are <2.5 micrometers in diameter another is coarse soot

particles (PM10) which are between 2.5 and 10 micrometers in diameter. Both particles

are smaller than the width of a human hair. The leading-edge research suggests that the

existences of even smaller particles are more damaging to health.

Hence the carbon soot of these automobile emissions needs to be monitored and

the measures to reduce them are to be initiated. Hence, in the present study, it is

proposed to measure the concentration of carbon soot of the automobile emissions of

motor vehicles of Hyderabad city in Andhra Pradesh with the instrument developed in

the present study.

Section 6.3

CALIBRICATION AND MEASUREMENT PROCEDURE

Before using the system for measurement of carbon soot in automobile

emission(8,9)

, the system must be calibrated by measuring a series of known standard

gases. In the present study, the system is calibrated at five concentrations of standard

carbon soot gases 10mg/m3, 50mg/m

3, 100mg/m

3, 200mg/m

3 and 500mg/m

3. The

following calibration procedure is followed in the measurement of carbon soot

pollutant.

1. Clean the photoacoustic resonant cell and keep it dry.

2. Connect the PA cell detectors to the electronic circuit.

3. Select the laser source and use in modulation mode.

4. Switch ON the hardware system and activate the software.

5. Switch ON the laser source and align the beam to resonant cell.

6. Purge the PA cell with nitrogen gas.

7. Fill the standard gas sample gas into PA cell according to the required

pressure.

8. Close inlet and outlet valves of PA cell tightly.

9. The measurement system measures and displays the gas concentration along

with temperature and pressure.

10. Repeat the steps from 6 to 9.

11. Note the readings of photoacoustic measurement system.

After making the appropriate adjustments in the hardware and following the

calibration procedure, the instrument is tested with the standard gases of carbon

soot(7,10)

. The outputs of the carbon soot measuring system are presented in Fig. 6.2.

The results of measurements are presented in Table 6.2. The measurements made are

compared with a Exhaust Gas Analyzer of Neptune Make (Model No.EGA200),

Mumbai, India and the results are presented in the same table. The results of the present

study are in good agreement with those obtained from the Gas analyzer.

Table 6.2 : Carbon soot measurement in standard gases

S. No. Standard values

(mg/m3)

Present study

(mg/m3)

Gas Analyzer*

(mg/m3)

1 10 9.4 9.5

2 50 49.0 49.3

3 100 98.6 99.0

4 200 196.5 197.2

5 500 493.7 495.2

*Exhaust Gas Analyzer (Model No.EGA200), Neptune Equipments, Mumbai, India.

Section 6.4

MEASUREMENT OF CARBON SOOT POLLUTANT

RESULTS AND DISCUSSION

The motor vehicles of Hyderabad as indicated in Table 6.3 are chosen for the

measurement of carbon soot of the automobile emissions. The samples are collected

from these motor vehicles. The concentration of carbon soot of these motor vehicles is

measured with the system designed and developed in the present study. The results of

the measurements are presented in Table 6.4. These measurements are also made with

the standard Exhaust Soot Analyzer (Model No. EGA200), Neptune equipments used in

Vimta Laboratory, Hyderabad. The results are presented the same table for comparison.

The results of the present study are in good agreement with those values obtained from

the standard gas analyzer.

The automobile emission samples from heavy-duty truck and passenger buses

have very high carbon soot levels. The emission samples from mini truck, seven seater

auto and city taxi vehicles comprise high concentration of carbon soot. The emission

samples from passenger auto and personal diesel car are having moderate black carbon

and remaining two emission samples from petrol car and motor cycles are having below

emission standards of pollution control board.

Table 6.3 : List of selected motor vehicles for measurement of carbon soot

S. No.

Motor vehicle

LocationLocationLocationLocation

ManufacturerManufacturerManufacturerManufacturer 1 Heavy-duty Truck

Balanagar, Ranga

Reddy District

Ashok Leyland

2 Metro City Bus Kukatpally, Hyderabad Tata Motors

3 Ordinary City Bus Kukatpally, Hyderabad Ashok Leyland

4 Eicher (Mini truck) Chintal, Hyderabad Eicher Motors

5 Passenger Auto KPHB Colony,

Hyderabad

Mahindra

Corporation

6 City Cabs Bharath nagar,

Hyderabad

Tata Motors

7 Private Diesel Car Sanathnagar,

Hyderabad

Maruthi Suzuki

8 Passenger Auto (Four

Seater)

Balanagar, Ranga

Reddy District

Mahindra

Corporation

9 Petrol Car Sanathnagar ,

Hyderabad

Mahindra

Corporation

10 Motor Cycle Sanathnagar,

Hyderabad

Bajaj Limited

Table 6.4: Carbon soot measurement in automobile emissions

S. No.

Test vehicle

Present study

(mg/m3)

Gas Analyzer*

(mg/m3)

1 Heavy-duty truck

432.5 433.4

2 Ordinary City Bus 385.5 386.2

3 Metro City Bus 340.6 341.1

4 Eicher (mini truck) 290.4 291.8

5 Seven Seater

Passenger Auto

253.2

254.1

6

City Cabs

227.5

228.2

7 Private Diesel Car

155.1 156.1

8 Passenger auto

(Four seater)

150.5 151.2

9 Petrol car 145.0 145.8

10 Motor cycle

115.7 116.6

*Exhaust Gas Analyzer (Model No.EGA200), Neptune Equipments, Mumbai, India.

REFERENCES

1. Ming Zheng, T. Graham Reader, and J. Gary Hawley, Journal of Energy

Conversion and Management, 45, 883, UK (2004).

2. C. F. Bohren and D. R. Huffman, “Absorption and Scattering of Light by Small

Particles”, John Wiley & Sons Publications, New York (1983).

3. C. Haisch and R. Niassner, Spectroscopy Europe, 14, 5, Germany (2002).

4. Ichiro Asano, “Measurement Systems for Diesel Exhaust Gas and Future

Trends”, Future article, Horiba, Japan (2000).

5. Lutz Kramer, Zoltan Bozoki and Reinhard Niessner, Journal of Analytical

Sciences, 17, 46, Japan (2001).

6. Dr. M.Gerspacher, “Carbon Black Characterization”, Sid Richardson Carbon Co.

Publishers, Texas, USA(1998).

7. W. Patrick Arnott, Hans Moosmuller, and John W. Walker, Review Science

Instrumentation, 71, 4545, USA (2000).

8. Dr. Sharad Gokhale, “Air Pollution Sampling and Analysis”, Laboratory

Manual, IIT of Guwahati, India (2009).

9. W. P. Arnott, H. Moosmuller, C. F. Rogers, T. Jin Bruch, Atmospheric

Environment, 33, 2845 (1999).

10. Hayri Serhat Sapmaz, “Soot Measurements in Steady and Pulsed Ethylene/Air

Diffusion Flames Using Laser Induced Incandescence”, Electronic Thesis and

Dissertations, Florida International University, USA (2006).

CHAPTER 7

Measurement of Carbon Monoxide Pollutant in

Industrial and Automobile Emissions

Section 7.1

INDUSTRIAL AND AUTOMOBILE EMISSIONS

Industries play an important role in the process of economic development in the

country. They enhance the economic welfare1 of citizens and supplies the material

goodsthey consume. The way in which society will develop in the future is largely

dependent on how the growth which industry generates in distributed. Industry is also a

major consumer of natural resources2 and a major contributor to the overall pollution

load. The relative contribution to the total pollution load is obviously higher for

industry-related pollutants. The industry sector emits both traditions air pollutants

(NOx, SOx, Organic substances and particulate matter) and newly-recognized pollutants

(specific toxic substances). The air pollutants of different industries emissions3 are

given in Table 7.1.

Automobile emissions are one of the greatest contributing agents of air pollution

in major cities across the globe. Driving a personal vehicle is the most polluting activity

of most citizens. The vehicle emissions4 contain a range of many toxic pollutants such

as carbon monoxide, sulfur dioxide, particulate matter, hydrocarbons, formaldehyde,

nitrogen dioxides, carbon soot and volatile organic compounds. The emission gases of

different vehicles are given in Table 7.2.

Table 7.1: Emission gases of different industries

S. No. Industrial sector Emission gases

1 Thermal power plant NOx, SOx, CO and HC

2 Iron and Steel NOx, SOx, H2S, CO, HC and Toxic chemicals

3 Pharmaceuticals SO2, NOx and CO

4 Rubber plants NOx, SOx, CO

5 Chemicals Organic chemicals

6 Petrochemicals NOx, SOx, H2S, CO, HC and Toxic chemicals

Table 7.2: Emission gases of motor vehicles

S. No. Motor vehicle Emission gases

1 Heavy-duty truck NOx, CO, VOCs and Carbon soot

2 Passenger vehicle (Bus) NOx, CO and Carbon soot

3 Mini truck NOx, CO, Carbon soot and VOCs

4 Passenger auto Carbon soot, CO and NOx

5 Light-duty truck (Diesel car) NOx, CO and Carbon soot

6 Motor cycle NOx, CO and VOCs

Section 7.2

INTRODUCTION TO CARBON MONOXIDE

Carbon monoxide (CO) is a colorless, odorless and tasteless air pollutant. It is widely

known as the silent killer. Carbon monoxide is highly toxic to human beings and

animals. It consists of one carbon atom and one oxygen atom. CO is produced from

incomplete combustion of carbon-containing fuels such as gasoline, natural gas, oil,

coal and wood. The largest anthropogenic5 source of CO in the India is vehicle

emissions. The motor vehicles produce carbon monoxide about 60% nationwide. In

urban areas the percentage exceeded 80%. The other sources are including industrial

processes, non-transportation fuel combustion and wildfires.

Health effects

Carbon monoxide is dangerous because it inhibits the blood's ability to carry oxygen to

vital organs such as the heart and brain. Inhaled CO combines with the oxygen carrying

hemoglobin of the blood and forms carboxyhemoglobin6 (COHb) which is unusable for

transporting oxygen. The health effects of various concentration of carbon monoxide are

given in Table 7.3.

Table 7.3: Health effects of various concentration of carbon monoxide

Exposure

(hours)

CO Concentration

(ppm)

Perceptible Sickness *Deadly

0.5 600 1000 2000

1 200 600 1600

2 100 300 1000

4 50 150 400

6 25 120 200

8 25 100 150

*A CO concentration of 12000 ppm is deadly after 1-3 minutes.

Thus the carbon monoxide of industrial and automobile emissions needs to be

monitored and the measures to reduce them are to be initiated. Hence, in the present

study, it is proposed to measure the concentration of carbon monoxide of automobile

and industrial emissions of motor vehicles, pharmaceutical and process industries7 of

Hyderabad and Rangareddy districts in Andhra Pradesh with the instrument developed

in the present study.

Section 7.3

CALIBRATION AND MEASUREMENT PROCEDURE

Before using the system for measurement of carbon monoxide in industrial and

automobile emissions, the system must be calibrated by measuring a series of known

standard gases. In the present study, the system is calibrated at seven concentrations of

standard carbon monoxide gases such as 10ppm, 50ppm, 100ppm, 200ppm, 500ppm,

1000ppm and 2000ppm. The following calibration procedure is followed in the

measurement of carbon monoxide pollutant.

1. Clean the photoacoustic resonant cell and keep it dry.

2. Connect the PA cell detectors to the electronic circuit.

3. Select the laser source and use in modulation mode.

4. Switch ON the hardware system and activate the software.

5. Switch ON the laser source and align the beam to resonant cell.

6. Purge the PA cell with nitrogen gas.

7. Fill the standard gas sample gas into PA cell according to the required

pressure.

8. Close inlet and outlet valves of PA cell tightly.

9. The measurement system measures and displays the gas concentration

along with temperature and pressure.

10. Repeat the steps from 6 to 9.

11. Note the readings of photoacoustic measurement system.

After making the appropriate adjustments in the hardware and following the

calibration procedure, the instrument is tested with the standard gases of carbon

monoxide. The outputs of the carbon monoxide measuring system are presented in Fig.

7.1. The results of measurements are presented in Table 7.4. The measurements made

are compared with a Gas Analyzer of Fluke Corporation make (CO-220), USA are

presented in the same table. The results of the present study are in good agreement with

those obtained from the Gas analyzer.

Table 7.4 : Carbon monoxide measurement in standard gases

S. No. Standard values

(ppm)

Present study (ppm) *CO Gas Analyzer

(ppm)

1 10 9.5 9.9

2 50 48.5 49.2

3 100 99.0 99.4

4 200 196.5 198.2

5 500 497.0 498.6

6 1000 996.5 998.0

7 2000 1989.0 1992.0

*Fluke CO-220, Fluke Corporation, USA.

Section 7.4

MEASUREMENT OF CARBON MONOXIDE POLLUTANT

RESULTS AND DISCUSSION

The industries and motor vehicles of Ranga Reddy district and Hyderabad as indicated

in Table 7.5 and Table 7.6 are chosen for the measurement of carbon monoxide8 of the

industrial and automobile emissions. The samples are collected from these industries

and motor vehicles(9,10)

. The concentration of carbon monoxide of these samples is

measured with the system designed and developed in the present study. The results of

the measurements are presented in Table 7.7. These measurements are also made with

the standard CO Gas Analyzer (Model No.CO-220), Fluke Corporation used in Ramky

Laboratory, Hyderabad. The results are presented the same table for comparison. The

results of the present study are in good agreement with those values obtained from the

standard gas analyzer. The system is successful for the measurement of carbon

monoxide in industrial and automobile emissions with an accuracy of ±1%.

The industrial emission samples from Thermax industries and Co-gen power

plant have very high carbon monoxide levels. The emission samples from Aurobindo

pharma, Likhita industries and Gulf oil corporations contain high concentration of

carbon monoxide. The emission samples from Paints industry and Mylan pharma are

having moderate CO and remaining one sample from Gland pharma are having below

emission standards of pollution control board.

The automobile emission samples from heavy-duty truck, passengers bus and

eicher truck have very high carbon monoxide levels. The emission samples from

personal diesel car and seven seater passenger auto comprises high concentration of

carbon monoxide. The emission samples from four seater auto and city cab are having

moderate CO and remaining two samples from petrol car and motor cycle are having

below emission standards(4,11)

of pollution control broad.

The embedded based photoacoustic system designed and developed in present

study is quite successful in the measurement of air pollutants - nitrogen oxides, carbon

soot and carbon monoxide in the given samples of industrial and automobile emissions

with an accuracy of ±1ppm.

Table 7.5 : List of selected industries for measurement of carbon monoxides

S. No. Name of industry Type of industry Location

1 Thermax industries Process Ranga Reddy

District

2 Co-gen power plant Power plant Ranga Reddy

District

3 Aurobindo Pharma Pharmaceutical Bachupally, Ranga

Reddy District

4 Likhita industries Process Hyderabad

5 Gulf oil corporation Process Hyderabad

6 Paints industry Paints Hyderabad

7 Mylan pharma Pharmaceutical Ranga Reddy

District

8 Gland pharma Pharmaceutical Ranga Reddy

District

Table 7.6 : List of selected motor vehicles for measurement of carbon monoxides

S. No.

Motor vehicle

PlacePlacePlacePlace

ManufacturerManufacturerManufacturerManufacturer 1 Heavy-duty Truck

Balanagar, Ranga

Reddy District

Ashok Leyland

2 Metro City Bus Kukatpally, Hyderabad Tata Motors

3 Eicher (Mini truck) Chintal, Hyderabad Eicher Motors

4 Passenger Auto KPHB Colony,

Hyderabad

Mahindra

Corporation

5 City Cabs Bharath nagar,

Hyderabad

Tata Motors

6 Private Diesel Car Sanathnagar,

Hyderabad

Maruthi Suzuki

7 Passenger Auto (Four

Seater)

Balanagar, Ranga

Reddy District

Mahindra

Corporation

8 Petrol Car Sanathnagar ,

Hyderabad

Mahindra

Corporation

9 Motor cycle Sanathnagar, Hyd. Bajaj Limited

Table 7.7 : Measurement of carbon monoxide of industrial emissions

S. No

Name of industry,

Location

Present study

(ppm)

CO Gas

Analyzer* (ppm)

1 Thermax industries,

Ranga Reddy District

1875.4 1878.6

2 Co-gen power plant 1823.0 1825.2

3 Aurobindo Pharma,

Bachupally, Ranga

Reddy District

1680.8

1682.6

4 Likhita industries,

Hyderabad.

1610.0

1612.4

5 Gulf oil corporation,

Hyderabad.

1584.0 1586.5

6 Paints industry, Ranga

Reddy District

1496.5 1498.1

7 Mylan pharma, Ranga

Reddy District

1368.5

1371.3

8 Gland pharma,

Jeedimetla, Ranga Reddy

District

1311.8

1313.2

*Gas Analyzer Model No. CO-220, Fluke Corporation, USA.

Table 7.8: Measurement of carbon monoxide of automobile emissions

S. No.

Test vehicle

Location Location Location Location

Present study

(ppm)

CO Gas

Analyzer*

(ppm)

1 Heavy-duty truck

Balanagar,

Hyderabad

1966.0

1968.6

2 Passenger City

Bus

Kukatpally,

Hyderabad

1830.0 1831.1

3 Eicher (mini

truck)

Chintal,

Hyderabad

1730.5 1731.8

4 Seven seater

Passenger auto

KPHB

colony, Hyd.

1533.0

1534.1

5 City cabs Bharath

nagar, Hyd.

1517.5

1518.2

6 Private Diesel Car

Sanathnagar,

Hyderabad

1495.0

1496.1

7 Passenger auto

(Four seater)

Balanagar,

Hyderabad

1480.5 1481.2

8 Petrol car Sanathnagar,

Hyderabad

1354.0 1355.9

9 Motor cycle

Sanathnagar,

Hyderabad

1315.0 1316.1

REFERENCES

1. P. Eugene, Journal of Environmental Economics and Management, 10, 112 (1983).

2. A.N. Fedorow and Konstantinov, Geography and Natural Resources, 30, 146

(2009).

3. Mark Jacobson, Journal of Geophysical Research, 115, 78 (2010).

4. Pranav Raghav Sood, Journal of Energy and Biotechnology, 33, 45, Singapur (2012).

5. Alan Robock, Reviews of Geophysics, 38, 191(2000).

6. J. Lopez-Herce , Borrego, Bustinza and Carrillo , Intensive Care Med. , 31, 1235

(2005).

7. V. Beschkov, “Pollution Control Technologies”, Pollution Control in Industrial

Proces Encyclopedia of Life Support Systems, Vol.III, Bulgaria.(2001)

8. M V L R Anjaneyulu., M Harikrishna and S Chenchuobulu, Journal of World

Academy of Science, Engineering and Technology,17, 135 (2008).

9. C.G.Teodoro, D.U Schramm and M.S. Sthel, “Photoacoustic Detection and

Moniotoring of Pollutant Gases from Urban Public Transport” International

Conference on Photoacoustic and Photothermal Phenomena, IOP Publishing,

Conference Series 214 (2010).

10. Sirajuddin Horaginamani, M Ravichandran, Journal of Science, Engineering and

Technology, 6, 13 (2010).

11. Emission Standards- India : On-Road Vehicles and Engines”, Dieselnet.com,

(2009).

LIST OF PUBLICATIONS AND PRESENTATIONS

1. M. Lakshmi Prasad, K. Malakondaiah and Ramesh Datla, “Design and Fabrication

of the Differential Photoacoustic Resonant Cell for Trace Gas Analysis” Jl. of

Instrum. Soc. Of India, Vol. 39, 231 (2009).

2. M. Lakshmi Prasad, K. Malakondaiah and Ramesh Datla, “Design and Development

of Photoacoustic Spectroscopy for Detection of NO2 using Compact Low Power

DPSS Laser”, International Pitcon Conference, Chicago, USA (2009).

3. M. Lakshmi Prasad, K. Malakondaiah and Ramesh Datla, “Design and Fabrication of

The Differential Photoacoustic Resonant Cell for Trace Gas Analysis” National

Symposium on Instrumentation (NSI) , Visakhapatnam, India (2008).

4. M. Lakshmi Prasad, K. Malakondaiah and Ramesh Datla, “Development of Laser

Based Photoacoustic Gas Analyser for Detection of Environmental Poollutants”,

International Eastern Analytical Symposium, New Jersey, USA (2010).

5. M. Lakshmi Prasad, K. Malakondaiah and Ramesh Datla, “Fabrication of the

Photoacoustic Resonant Cell for Gas Analysis” International Pitcon Conference, USA

(2010).