measurements & instrumentation.

HAI EVERYBODY…

Be the best in ever…

By …

Pavithra.S

SMART SENSORS

UNDER THE TOPIC OF TRANSDUCER

INTRODUCTION DEFINTION USEFULLNESS OF SILICON

TECHNOLOGY IN SMART SENSOR SIGNAL CONVERSION EFFECTS ENHANCEMENT OF APPLICATION SYSTEM RELIABILITY BETTER SIGNAL NOISE RATIO IMPROVEMENT IN

CHARACTERISTICS GENERAL ARCHITECTURE OF

SMART SENSOR

SUMMARY

WHAT IS MEANT BY TRANSDUCER?.... TRANSDUCER IS DEFINED AS A DEVICE THAT RECEIVES ENERGY FROM

ONE SYSTEM AND TRANSMITS TO ANOTHER. (WHICH CONVERTS PHYSICAL QUANTITY

INTO ELECTRICAL SIGNAL)IT’S ALSO CALLED AS ‘PICKUP’

TRANSDUCER

DEFINITION [Sensor means which detects/measures

the device Example: thermometer SMART SENSOR WITH INTEGRATED

ELECTRONICS THAT CAN PERFORM ONE OR MORE OF THE FOLLOWING FUNCTION….

LOGIC FUNCTIONS TWO WAY COMMUNICATION MAKE DECISIONS…..

Usefulness of silicon technology in smart sensor

convincing advantages of using silicon technology as integrated circuits. Sensor is made with a same technology as integrated circuits. it utilizes the properties of silicon (GaAs).

a transduction element either includes thin metal films,zinc oxide & polymeric films

integrated sensors provide significant advantages in terms of overall sizes & the ability to use small signals from the transduction element.

IC (integrated circuit) industry will get involved in smart sensor if a very large market can be captured &the production of smart sensor doesn’t require non-standard processing steps…..

Signal domain examples

Radiant Light intensity,polarization,phase, wavelength

mechanical Force,pressure,flow,vaccum, thickness

thermal Temperature,temp gradient,thickness

chemical Concentration,toxicity,pH

magnetic Field intensity,flux density,permeability

Signal conversion effects

Signal domain examples

Radiant Photo voltaic effect,photo electric effect,photo magneto-electric effect,photo conductivity

mechanical Piezo resistivity

thermal Seebeck effect,temperatre dependence of conductivity

chemical Ion sensitive field effect

magnetic Hall effect,magneto resistance

Radian signal domain:Radiant silicon can be used to connect a sensor for sensing wide range of radiant signal from gamma rays to infrared. Silicon can be used for the fabrication of photoconductors,phototransistor or to detect nuclear radition.

silicon can be used for measuring force and pressure because of the piezo resistance effect.

This effect is large because the average mobility of electrons and holes in siliconis strongly affected by the application of strain

silicon can alo be used for the measurement of air or gas velocities.

Mechanical signal domain

Smart sensor also enhances the following applications:

self calibration- adjusting some parameter of sensor during fabrication.

-calibration is needed bcoz, their adjustments usually change with the time that needs the device to be removed & recalibrated.thee problems are solved by

smart sensor(has the the correction functions in memory).

Enhancement of application

computation- it also allows one to obtain the average, varience & standard deviation for set of measurement.this can be easily done done using smart sensor

- to compensate for the environmental change such as temperature.

communication- communication means of exchanging or conveying information.

multisensing – a single smart sensor can measure pressure ,temperature,humidity, gas flow &infra red….

System reliability System reliability is significantly improved due to the utilization of smart sensors

Non linearity Cross sensitive(shows an un desairable

sensitivity to strain &temperature ) Offset(well reduced by sensitivity reduction

method) Parameter drift & componeent values(these

are functions of time it can be solved by automatic calibration)

Improvement in characteristics

Thermal signal domain- measurement of temperature by using two bipolar transistors with a cons.ratio of emitter current.

Magnetic signal domain-silicon is a non magnetic material. But it can be used for the construction of hallplates &transistor structure that are sensitive to magnetic fields.

Chemical signal domain-ISFET is suitable for such application.

Signal domains

The presence in smart sensor has led to corrections for different un desirable sensor characteristics which include,

input offset &span variation, non linearity & cross sensitivity .as these are carried in software no additional software is required

thus calibration becomes an electronic process

Importance &adoption of smart sensor

Sensor inside hardware is more complex in the sensor on the other hand it is outside the sensor.

Reduced cost of bulk cables & connectors

To reduce the cost of bulk cables & connectors needed to connect different blocks

Cost improvement

Block diagram

General architecture of smart sensor

Transducer 1

Transducer 1

Transducer 1

Transducer 1

A1

A1

A1

A1

S/H1

S/H2

S/H3

S/H4

ANALOG MUX

ADC

Offset correction& temp drift

compensation

sample&Hold control

processor Serial communication

memory DAC