Smart Fuel Measurement System

8/7/2019 Smart Fuel Measurement System

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SMART FUEL

MEASUREMENT SYSTEM

Anand Rangaswamy

6th Semester,Electrical & Electronics

SJCE,[email protected]



2/25/2011 Smart Fuel Measurement System 2

If you're like me, you like to squeeze every last mile

you can out of your tank of fuel .

If you could get 20 useful miles extra from eachtank, that could save you two or three trips to the

gas station over the course of a year .

� Present Day System

*Notoriously inaccurate,analog system

*Shows empty when there are gallons left*Shows full for the first 50 miles

*SMS conceived because students my

age end up pushing their bikes




Present Day Measurement System

� Simplest method

� Based on buoyancy effect� Mechanically coupled to displacement

sensor such as a simple pot

� Error in the instrument is inversely

proportional to the area of the float




Mechanism:The Sending Unit

Basically consists of � Float made of foam connected to a rod

� Mounted onto a variable resistor by meansof a wiper,which is grounded on one side

� The current that flows is proportional to theposition of the wiper which in turn dependson the amount of fuel present

� As the fuel level goes down the float sinksand hence the wiper moves over the potcausing a decrease in current Click Here




Reasons for Inaccuracy

� Fuel has to drop below a certain levelbefore the float starts to drop.Its upwardmovement is limited either by the link it is

connected to or the top of the tank � Similarly,the range of movement does not

extend to the very bottom of the tank

� Shape of the tank ,it may be made of plasticmolded to fit around tight spaces




Disadvantages� The error in measurement is inversely proportional

to the cross sectional area of the float. The

manufacturer does not have the freedom to design

an efficient space saving design of the tank

� The device is not linear,zero on the gauge would

correspond to a few litres in reality

� The float mechanism is affected by the

disturbances to the level of the fluid

� The float mechanism is erroneous on inclines




The New Design� Reads accurately, state of the art technology

� Uses appropriate sensors

� Converts analog signals to digital signals

� Uses a microprocessor




Factors Considered While

Selecting Sensors� Nature of required

measurement

� Nature of output

� Range

� Accuracy

� Linearity

� Speed of response

� Maintenance,life

� Power requirement

� Availability & cost

� Reliability




Probable Pressure Sensors� Bourdon tube

� Piezoelectric Load Cells

� Diaphragm Pressure Sensors

� Bellow pressure sensors

� Load cells




Why Load Cells?� Versatile for this application

� Satisfies all requirements

� Can operate over wide range of forces

� Most popular sensor in the industry




What AreLoad Cells?� Electro mechanical sensors to measure static

and dynamic forces

� Consists of strain gauges

� Load on the load cell causes strain on the

gauge which is measured in volts per unitforce

� Shape and location of the gauge chosen suchthat both compressive and tensile forces act

on it

� The deformation of the load column of transducer causes strain at the surface

changing resistance






Characteristics of A Strain Gauge

� Gauge length,width

� Gauge sensitivity

� Range of measurement

� Accuracy

� Ability to withstand ambient environmentalconditions




Electrical Strain Gauges

� Principle based on measurement of changein R,L,C that are proportional to straintransferred to the specimen

� Usually 4 strain gauges are mounted 2 radially and 2 axially

� This arrangement permits a full wheatstonebridge that allows greater accuracy

� Any change in ambient temperature willaffect all four gauges similarly and willcancel out




Temperature changes

� Changes in temperature affect resistance of

the gauge,can cause an error

� To overcome this an unstrained

compensating gauge having the sametemperature characteristics as the active

gauge is to be used in the bridge

circuit,mounted close to the active gauge




Problems Faced With Strain

Gauges� Gauges are sensitive to temperature,which

increases r,such changes can be falselyinterpreted as pressure change

� The output of a strain gauge is very smalland has to be amplified with some error dueto noise signals in the amp

� An electrical bridge circuit solves bothproblems




The New Design

� Number of load cells under the tank

� The weight of the tank & fuel acts on theload cells causing change in resistance

which is read as change in voltage

� This is measured by the bridge circuit and isamplified







Prerequisites

� To determine force exerted by the fuel per

unit value of fuel volume

� We have to note down the value of changein voltage produced by the required amount

of fuel depending on our resolution� We can then set the least count by

calibrating the system to that minimumamount of fuel,say 100 ml

� The microprocessor stores the odometer reading each time the fuel goes down bysome amount, ideally 1 litre




� The data for the last 10 litres is stored and

with some manipulation on the data theaverage mileage can be calculated

� Depending on the amount of fuel left the

microprocessor can predict how far the car

can run without a refill




Advantages of the Proposed

System

� More accurate than the existing system

� This system is not affected by inclines

� No electrical part inside the tank,safety is

enhanced

� The system is independent of shape of the

tank

� The device can be made linear




Disadvantages� This method may not be directly applicable

to pick up trucks and motorbikes without

modifications

� The new system is more expensive,however

most present day cars come equipped with

a microprocessor,the cost wouldn¶t be ahindering block




References

� Instrumentation technology ± Jones

� Instrumentation fundamentals andapplications ± Morrison

� Industrial instrumentation ± Tata Mangalam

& R.Padmanabhan� Mechatronics ± W.Bolton

� Instrumentation Devices & Systems - C.S.Rangan, G.R. Sarma, V.S.V. Mani

� Measurements Systems Application AndDesign ± Ernest O Doeblin



THANK YOU!

QUESTIONS?

Smart Fuel Measurement System

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