February 18, 2005February 18, 2005

RIT RIT Formula SAE Data Formula SAE Data AcquisitionAcquisition

Team 05109Team 05109

TTeeam Membersam MembersJustin LaChausse Justin LaChausse –– Project LeaderProject Leader

BS Mechanical Engineering, Auto OptionBS Mechanical Engineering, Auto Option

Robert Doll Robert Doll –– Chief EngineerChief EngineerBS Mechanical EngineeringBS Mechanical Engineering

Zach BushZach BushBS Mechanical Engineering, Auto OptionBS Mechanical Engineering, Auto Option

John Howard Jr.John Howard Jr.BS Mechanical Engineering, Auto OptionBS Mechanical Engineering, Auto Option

Shuangbo (Bo) XuShuangbo (Bo) XuBS Electrical EngineeringBS Electrical Engineering

Hsiang Chi (Sean) HuiHsiang Chi (Sean) HuiBS Electrical EngineeringBS Electrical Engineering

Dr. Alan NyeDr. Alan NyeCoordinator/Faculty MentorCoordinator/Faculty Mentor

AAgegendanda

Sponsor Profile/NeedsSponsor Profile/Needs

Project GoalsProject Goals

Concept DevelopmentConcept Development

Feasibility AssessmentFeasibility Assessment

Financial OverviewFinancial Overview

Preliminary Design OverviewPreliminary Design Overview

Next StepsNext Steps

SSponsorponsor Profile Profile RIT Formula SAE RIT Formula SAE

Approximately 20 studentsApproximately 20 studentsDesign, Fabricate, and Race a Design, Fabricate, and Race a FormulaFormula--Style Race CarStyle Race Car

Compete Twice Annually at FSAE Compete Twice Annually at FSAE Competitions in Detroit and Competitions in Detroit and AustraliaAustralia

Vehicle SpecificationsVehicle Specifications4130 Steel Space Frame4130 Steel Space FrameUnequal/Unparallel AUnequal/Unparallel A--Arm Pull Arm Pull Rod SuspensionRod SuspensionHonda CBR600 F2 EngineHonda CBR600 F2 EngineAutronicAutronic Engine Management Engine Management SystemSystemZexelZexel--TorsenTorsen Type II DifferentialType II DifferentialRIT Designed Brake SystemRIT Designed Brake SystemThree Piece Composite BodyThree Piece Composite Body

DData Acquisition Overviewata Acquisition Overview

Electronic devices used to Electronic devices used to monitor vehicle parametersmonitor vehicle parameters

Sensor outputs recorded by Sensor outputs recorded by onon--board data loggerboard data logger

Data transmitted to PC for Data transmitted to PC for analysisanalysis

RIT FSAE currently owns a RIT FSAE currently owns a Competition Data Systems Competition Data Systems (CDS)(CDS) Commander II systemCommander II system

A data-acquisition processor (red box) mounted in a CART car.

Source: http://Source: http://www.machinedesign.comwww.machinedesign.com

MMisission Statement/Goalssion Statement/Goals

Team Mission StatementTeam Mission StatementDesign, assemble, and implement a stand alone Data Design, assemble, and implement a stand alone Data Acquisition (DAQ) System for a Formula SAE racecar. Sensor Acquisition (DAQ) System for a Formula SAE racecar. Sensor outputs will be recorded and manipulated to yield meaningful outputs will be recorded and manipulated to yield meaningful data about vehicle performance. Design emphasis will be data about vehicle performance. Design emphasis will be placed on system layout, sensor integration, and electrical placed on system layout, sensor integration, and electrical system capability.system capability.

Project GoalsProject GoalsProvide fully functioning data acquisition package and Provide fully functioning data acquisition package and recommendations for improving electrical systemrecommendations for improving electrical systemDemonstrate system capabilities through design verificationDemonstrate system capabilities through design verificationProvide RIT Formula SAE with an advantage over the Provide RIT Formula SAE with an advantage over the competitioncompetition

PProject Requirementsroject RequirementsRedesign DAQ SystemRedesign DAQ System

Team shall use a CDS Commander II Data LoggerTeam shall use a CDS Commander II Data LoggerEvaluate current system capabilitiesEvaluate current system capabilitiesDetermine feasible vehicle parameters to logDetermine feasible vehicle parameters to logDetermine appropriate sensors for useDetermine appropriate sensors for use

Integration on VehicleIntegration on VehicleDAQ system shall not interfere with operation of car subsystemsDAQ system shall not interfere with operation of car subsystemsComponents must be removable without affecting the vehicle’s abiComponents must be removable without affecting the vehicle’s ability to operatelity to operateOptimize strength vs. weight of mounting pickups and sensorsOptimize strength vs. weight of mounting pickups and sensors

Electrical System AnalysisElectrical System AnalysisDetermine current system loads without DAQ systemDetermine current system loads without DAQ systemDetermine added load on system, with DAQ incorporatedDetermine added load on system, with DAQ incorporatedOptimize electrical system to increase excess capacity for DAQ sOptimize electrical system to increase excess capacity for DAQ system and ystem and other potential electrical systems without negatively affecting other potential electrical systems without negatively affecting engine engine performanceperformance

Demonstration of DAQ CapabilityDemonstration of DAQ CapabilityDemonstrate characterization of car capabilitiesDemonstrate characterization of car capabilitiesDemonstrate optimization of car characteristicsDemonstrate optimization of car characteristicsDocument a procedure(s) used to demonstrate system capabilityDocument a procedure(s) used to demonstrate system capability

CConcept Developmentoncept Development

Data AcquisitionData AcquisitionLong ListLong List

Included all attainable vehicle parametersIncluded all attainable vehicle parametersBasic System (Baseline)Basic System (Baseline)

Minimum parameters needed to provide useful dataMinimum parameters needed to provide useful dataIntermediateIntermediate

Combination of Long List, and Basic SystemCombination of Long List, and Basic SystemHybridHybrid

Intermediate system split into several optional configurationsIntermediate system split into several optional configurationsMakes efficient use of data logger capabilities through channel Makes efficient use of data logger capabilities through channel allocationallocation

CConcept Developmentoncept DevelopmentElectrical SystemElectrical System

Assess Problems With Existing SystemAssess Problems With Existing SystemBattery is running at its limitBattery is running at its limitRectifier is running hot, may not handle the loadRectifier is running hot, may not handle the loadSuspecting current drain somewhere in systemSuspecting current drain somewhere in systemCannot integrate any more electrical componentsCannot integrate any more electrical components

Obtain Measurements of System LoadsObtain Measurements of System LoadsBatteryBattery

Quantify discharge rate of batteryQuantify discharge rate of battery

Rectifier/RegulatorRectifier/RegulatorDetermine temperature operating range in current setupDetermine temperature operating range in current setupMeasure output current during vehicle operationMeasure output current during vehicle operation

Overall SystemOverall SystemMeasure the current draws across each system componentMeasure the current draws across each system component

FFeasibility Assessmenteasibility Assessment

System LevelSystem Level

Setup 1 Setup 1 –– Current DAQ BoxCurrent DAQ BoxSetup 2 Setup 2 –– Two DAQ BoxesTwo DAQ BoxesSetup 3 Setup 3 –– Upgraded DAQ BoxUpgraded DAQ Box

Results show upgraded data Results show upgraded data logger is most feasible, given logger is most feasible, given available resourcesavailable resources

Hybrid system chosen due to Hybrid system chosen due to efficient use of logger capabilitiesefficient use of logger capabilities

Setup 1 Setup 2 Setup 3

Question 1 3 4 2Question 2 3 3 3Question 3 3 4 3Question 4 3 4 4

Question 1 3 4 3Question 2 3 4 4

Question 1 3 3 2Question 2 3 4 4

Question 1 3 4 2

Technology

Economics

Performance

Schedule

DAQ System Level Feasibility Assessment

0

1

2

3

4TQ 1

TQ 2

TQ 3

TQ 4

EQ 1EQ 2

PQ 1

PQ 2

SQ 1

Setup 1

Setup 2

Setup 3

FFeasibility Assessmenteasibility AssessmentSensor LevelSensor Level

Video system will not be usedVideo system will not be usedCDS Overlay System most CDS Overlay System most valuable, but too expensivevaluable, but too expensive

Pitch/Roll calculated in softwarePitch/Roll calculated in softwareLaser ride height sensors Laser ride height sensors desired, but too expensivedesired, but too expensive

String Potentiometer on steering String Potentiometer on steering columncolumn

Driveshaft torque sensors too Driveshaft torque sensors too expensiveexpensive

Economics ScheduleSensor Type TQ 1 TQ 2 TQ 3 TQ 4 EQ 1 PQ 1 PQ 2 SQ 1

Remote Camera 3 3 4 1 2 3 2 3CDS Data Overlay System 4 3 4 4 1 3 4 3Lipstick Camera 3 3 4 1 2 4 2 3

CDS Software Calculations 3 3 4 3 3 4 2 3Laser Ride Height Gages 4 4 4 3 1 3 4 3Trailing Wheels 3 3 3 3 3 2 3 2Gyroscope 4 4 4 3 2 3 3 3

String Dash Pot mounted on Steering Rack

2 4 4 4 4 4 4 2

String Dash Pot with Pulley on Steering Shaft

4 4 4 4 4 4 4 4

Strain Gages on Push/Pull rods with math using Motion Ratios

3 3 3 3 3 3 3 3

Strain Gages on Push/Pull rods with Calibration to Corner Loads

3 3 3 3 3 3 4 3

Laser Ride Height Gages 3 3 3 3 1 3 4 3Calculated in Trackmaster 3 3 3 3 4 4 3 3

Remote Torque Sensors 3 2 2 2 1 3 4 3

PerformanceTechnology

Onboard Video System

Pitch/Roll Angle/Rate

Steering Wheel Angle

Corner Weights

Ride Height

Driveshaft Torque

DDesign esign –– System LayoutSystem Layout

Hybrid SystemHybrid System

Competition SystemCompetition SystemSimultaneous data collection Simultaneous data collection of necessary parametersof necessary parameters

Test ConfigurationsTest ConfigurationsBrake SystemBrake SystemEngine SystemEngine System

Decision based on efficient Decision based on efficient use of data logger capabilitiesuse of data logger capabilities

Financial ConsiderationsFinancial Considerations

Analog Channel Overall Competition Setup Secondary Testing Concept1 Front Brake Line Pressure Front Brake Line Pressure2 Rear Brake Line Pressure Rear Brake Line Pressure3 Front Brake Rotor Temperature Steering Angle4 Rear Brake Rotor Temperature Lateral Acceleration5 Front Brake Pad Temperature Longitudinal Acceleration6 Steering Angle Vertical Acceleration7 Lateral Acceleration Yaw Rate8 Longitudinal Acceleration Left Front Shock Travel9 Vertical Acceleration Right Front Shock Travel10 Yaw Rate Left Rear Shock Travel11 Left Front Shock Travel Right Rear Shock Travel12 Right Front Shock Travel Left Front Pullrod Load13 Left Rear Shock Travel Right Front Pullrod Load14 Right Rear Shock Travel Left Rear Pullrod Load15 Left Front Pullrod Load Right Rear Pullrod Load16 Right Front Pullrod Load Throttle Position17 Left Rear Pullrod Load Manifold Air Pressure18 Right Rear Pullrod Load Air/Fuel Ratio19 Throttle Position Oil Temperature20 Manifold Air Pressure Water Temperature Inlet21 Air/Fuel Ratio Water Temperature outlet22 Flow rate through radiator2324

RPM Channel1 Front Wheel Speed Front Wheel Speed2 Left Rear Wheel Speed Left Rear Wheel Speed3 Right Rear Wheel Speed Right Rear Wheel Speed4 Differential Housing Speed Differential Housing Speed5 Engine RPM Engine RPM

BBudgetudgetLine # Vendor Description Item Total Line Total

Expenses

Equipment Purchases Under $1500Supplies-Off ice (includes printing, copying, computer supplies) 50.00$ Postage and Freight 75.00$ Electrical w ire, connectors, heat shrink tubing 350.00$

71551733 MSC (24) 0.220 Diameter/0.500 Thick Magnets 23.52$ SEN-9 CDS 1-1000 psi Pressure Sensor 255.00$

Tiger Direct Laptop Computer 700.00$ MC5 CDS 4 mb Memory Card 575.00$

Omega Strain Gauge Set 200.00$ WBo2 2CO Tech Edge Wideband O2 Control Unit (includes w iring and connectors) 275.00$ SEN-12S CDS (4) Strain Gauge Amplif iers 1,200.00$ 3,703.52$

Equipment Purchases Over $1500COM2-30 CDS 24 Analog, 5 RPM Commander II Logger 4,250.00$ 4,250.00$

TOTAL EXPENSES 7,953.52$

Income

Competition Data Systems Sponsorship 2,383.00$ Discount on COM2-30 2,180.00$ 10% off SEN-9 25.50$ 10% off SEN-12S 120.00$ 10% off MC5 57.50$

RIT Formula SAE Project Sponsorship 1,000.00$

TOTAL INCOME 3,383.00$

4,570.52$ TOTAL ACCOUNT STANDING

DDesign esign –– System OverviewSystem Overview

COM2COM2--30 Commander II Data 30 Commander II Data LoggerLogger

24 Analog, 5 Digital RPM 24 Analog, 5 Digital RPM ChannelsChannelsRemovable PCMCIA Memory Removable PCMCIA Memory CardCard

Track Master 2000 Analysis Track Master 2000 Analysis SoftwareSoftware

Generate Course MapsGenerate Course MapsUser Configurable Math User Configurable Math ChannelsChannelsExport Data to Other Analysis Export Data to Other Analysis ProgramsPrograms

COM2COM2--30 Data Logger30 Data Logger

Track Master 2000 Analysis Software

DDesign esign -- BrakesBrakesFront and Rear Brake Line PressuresFront and Rear Brake Line Pressures

(2) CDS pressure sensors placed in(2) CDS pressure sensors placed in--linelineDetermination of brake bias, caliper clamping Determination of brake bias, caliper clamping force, pad coefficient of frictionforce, pad coefficient of friction

Brake Pad TemperatureBrake Pad TemperatureEmbedded KEmbedded K--Type ThermocoupleType ThermocoupleControlled durability and fade resistance testingControlled durability and fade resistance testingQuantitative testing and analysis of pad material Quantitative testing and analysis of pad material performanceperformance

Rotor Surface TemperatureRotor Surface TemperatureInfrared PyrometerInfrared PyrometerData for heat transfer analysis, correlation to pad Data for heat transfer analysis, correlation to pad performanceperformance

SENSEN--9 Fluid Pressure Sensor9 Fluid Pressure Sensor

DDesign esign –– DrivetrainDrivetrain

Torque on Torque on DriveshaftsDriveshaftsRemote Torque SensorsRemote Torque SensorsCharacterizes differential performance Characterizes differential performance and under conditions of no wheel slip, and under conditions of no wheel slip, engine output torqueengine output torqueNot economically feasibleNot economically feasible

Front/Rear Wheel SpeedFront/Rear Wheel Speed(3) Hall Effect Sensors(3) Hall Effect SensorsObserve differential characteristicsObserve differential characteristicsIntegration with ECU for traction Integration with ECU for traction controlcontrol

Pi Research Torque SensorsPi Research Torque Sensors

Bosch HABosch HA--P Hall Effect SensorP Hall Effect Sensor

DDesign esign –– DrivetrainDrivetrain

Front Wheel Front Wheel –– DetailDetail

Rear Wheel Rear Wheel -- DetailDetail

DDesign esign –– Vehicle DynamicsVehicle Dynamics

SENSEN--28 Three Axis Accelerometer28 Three Axis Accelerometer

SENSEN--37 Yaw Rate Sensor37 Yaw Rate Sensor

Lateral, Longitudinal, Vertical Acceleration RatesLateral, Longitudinal, Vertical Acceleration Rates

GG--G Plots (Traction Circle)G Plots (Traction Circle)

Gyroscope can be used to measure yaw, pitch, or Gyroscope can be used to measure yaw, pitch, or roll rate depending on orientationroll rate depending on orientation

Oversteer/UndersteerOversteer/Understeer BalanceBalance

SkidpadSkidpad PerformancePerformance

Corner Entry/Exit PerformanceCorner Entry/Exit Performance

DDesign esign –– SuspensionSuspension(4) Coil over damper displacement (4) Coil over damper displacement measurementsmeasurements

(4) Linear Potentiometers(4) Linear PotentiometersRide height at each cornerRide height at each cornerDamper StrokeDamper StrokeDamper VelocityDamper VelocityCalculate Pitch AngleCalculate Pitch AngleApproximate Roll AngleApproximate Roll Angle

Integration considerations for proper Integration considerations for proper calibrationcalibration

KinematicKinematic ModelModel SENSEN--20 Displacement Sensor20 Displacement Sensor

DDesign esign –– SuspensionSuspension

Rear Suspension Rear Suspension -- DetailDetail Front Suspension Front Suspension -- DetailDetail

DDesign esign –– SteeringSteering

Steering Wheel AngleSteering Wheel Angle

String Rotary PotentiometerString Rotary Potentiometer

Inside and outside tire steer anglesInside and outside tire steer angles

Driver FeedbackDriver Feedback

Oversteer/understeerOversteer/understeer balancebalance

Ergonomic packaging considerationsErgonomic packaging considerations

DDesign esign –– Corner LoadsCorner Loads

Develop system to measure vertical load on each tire

Use suspension pull rods

Load Cells Desired (high cost)

Strain Gauges with amplifiers

Quantify load transfer

Design loads

Pad and tire coefficient of friction

DDesign esign –– Corner LoadsCorner Loads

Strain Gage MeasurementStrain Gage MeasurementExtremely low change in Extremely low change in resistanceresistance

In our case, roughly 0.17In our case, roughly 0.17ΩΩwith a 350with a 350ΩΩ gagegage

Wheatstone BridgeWheatstone BridgeQuarterQuarter--BridgeBridge

1 Active gage1 Active gage

HalfHalf--BridgeBridge2 Active gages2 Active gages

FullFull--BridgeBridge4 Active gages4 Active gages

Half & FullHalf & Full--Bridge eliminate Bridge eliminate temperature affects!temperature affects!

Wheatstone Bridge

Quarter-Bridge

Half-Bridge Full-Bridge

Design Design –– Corner LoadsCorner Loads

Signal ConditioningSignal ConditioningBridge completionBridge completion

High precision reference High precision reference resistorsresistorsRR22 = 350= 350ΩΩRR11 = 300= 300ΩΩ resistor + 100resistor + 100ΩΩtrim pottrim pot

Allows for offset nullingAllows for offset nulling

Excitation voltageExcitation voltage3V 3V –– 10V power supply to 10V power supply to bridgebridge

Remote SensingRemote SensingVoltage drop due to distance Voltage drop due to distance from excitation source to from excitation source to gagegageNegative feedback amplifiers Negative feedback amplifiers compensate for lead lossescompensate for lead losses

ContinuedContinuedAmplificationAmplification

Output from bridge is in mVOutput from bridge is in mVCDS unit requires signal to be CDS unit requires signal to be in Voltsin VoltsAD8230 can amplify signalAD8230 can amplify signal(G = 1 (G = 1 –– 1000)1000)

FilteringFilteringLow pass filters can eliminate Low pass filters can eliminate noisenoise

Shunt CalibrationShunt CalibrationCreate a known Create a known ∆∆RRSimulates an applied strainSimulates an applied strainCompare resultsCompare results

DDesignesign –– Corner LoadsCorner Loads

Preliminary DesignPreliminary DesignHalfHalf--bridge circuitbridge circuit

Signal amplification with AD8230Signal amplification with AD8230ConcernsConcerns

Not enough strain to produce accurate resultsNot enough strain to produce accurate resultsRemote sensing may be requiredRemote sensing may be required

DDesign esign –– EngineEngine

Engine RPMEngine RPMExisting hall effect sensor on Existing hall effect sensor on crankshaftcrankshaft

Driver feedbackDriver feedbackGear positionGear position

Throttle PositionThrottle PositionExisting rotary potentiometerExisting rotary potentiometer

Driver feedbackDriver feedbackManifold Air PressureManifold Air Pressure

CDS MAP SensorCDS MAP SensorEngine loadEngine load

Air/Fuel RatioAir/Fuel RatioWideband OWideband O22 Sensor and Sensor and controllercontroller

Engine tuningEngine tuning Tech Edge 2CO Wideband UnitTech Edge 2CO Wideband Unit

Bosch RP 86 Rotary PotentiometerBosch RP 86 Rotary Potentiometer

CCurrent Electrical Systemurrent Electrical System1

2

12

Cooling Fan

Brake light

+

0

+

Ign

15

Author: F. Fiore; Resource: www.autronic.com <RevCode>

RIT Formula SAE, Race car wiring diagram

A

1 1Thursday, January 27, 2005

Title

Size Document Number Rev

Date: Sheet of

OilPressureSwitch

8

+12V

12

M

12

-

Ign RelayFuel PumpRelay

+

44

Ign2

Autronic SM2 Engine Management

+

Tacho

L -

10

Starter Signal

Sender

Ign1

3

0

Neutral Switch(Transmission)

IgnIgn

17

Starter Relay

V112Vdc

+12V

T/C Enable

Ign2

7

A

15

Brake O/T Relay + SWitch

-

+

Fuel Pump

1

9

L

12

1

2

Brake Pressure Switch

Oil TempWater Temp

12

45 18

+12V

1

2

R

49

Ign1

Ign(

-)

Ign Switch

1 21

2

46

Starter Motor

+ +6

12

12

14 13

Alternator

12

12

Oil WarningLight

Starter Button

+

1

2

M

40

-

Kill Switch

L

Ign Switch

Cooling FanRelay

Sender

Neutral Light

48

Autronic Capacitive DischargeIgnition

12

1

2

Rectifier/Regulator

Ign(

-)

CCurrent Electrical Systemurrent Electrical System

Primary ComponentsPrimary Components12V Battery12V BatteryStarter MotorStarter MotorAutronicAutronic SM2 Engine Control SM2 Engine Control UnitUnitAutronicAutronic Capacitive Discharge Capacitive Discharge IgnitionIgnition

0.770.77--2.9A Current Draw2.9A Current DrawCharging SystemCharging System

Alternator/Rectifier/RegulatorAlternator/Rectifier/RegulatorSH693SH693--12 from a Honda 12 from a Honda CBR600 F2 MotorcycleCBR600 F2 Motorcycle

Full Wave 3 Phase AC to DCFull Wave 3 Phase AC to DCCooling FanCooling Fan

6.6A Current Draw6.6A Current DrawFuel PumpFuel Pump

10A Current Draw10A Current Draw

Source: http://Source: http://www.allaboutcircuits.comwww.allaboutcircuits.com

DDesign esign –– ElectricalElectrical

Potential System ImprovementsPotential System Improvements

BatteryBatteryMove battery away from exhaust and add insulatorMove battery away from exhaust and add insulatorDifferent cell technologyDifferent cell technologyUpgrade to higher capacity battery Upgrade to higher capacity battery

Rectifier/RegulatorRectifier/RegulatorNew rectifier/regulatorNew rectifier/regulatorSilicon paste to improve heat flowSilicon paste to improve heat flow

Reduce WeightReduce WeightReducing sizes of wire, meanwhile supporting enough currentReducing sizes of wire, meanwhile supporting enough current

NNext Stepsext Steps

Finish electrical system analysis and finalize Finish electrical system analysis and finalize recommendations for improvementsrecommendations for improvements

Prototype fabrication of strain gauge amplifiersPrototype fabrication of strain gauge amplifiers

Fabricate parts and wiring harness, assemble systemFabricate parts and wiring harness, assemble system

Develop basic optimization tests to prove system Develop basic optimization tests to prove system functionalityfunctionality

Document DAQ system use and calibration proceduresDocument DAQ system use and calibration procedures

SSpringpring Quarter TimelineQuarter Timeline

Website

Poster

Final Design Report

Testing Procedures/Report

Calibration Procedure

Documentation

Chassis Optimization

Sensor Verification

Sensor/Software Calibration

DAQ Calibration/Testing

Electrical Wiring

Final Schematics

Completed Electrical System

Integration onto Car

Bracket Manufacture

Final Bracket Design

Completed DAQ System

Completed System

10987654321

Week - Spring Quarter

Item Breakdown

AAcknowledgementscknowledgements

Dr. Mark Dr. Mark KempskiKempski

Mr. John D. Mr. John D. WellinWellin

Mr. Dave HathawayMr. Dave Hathaway

Competition Data Systems Inc.Competition Data Systems Inc.

Mr. Fernando Fiore (RIT Formula SAE)Mr. Fernando Fiore (RIT Formula SAE)

Mr. Robert Hammond (RIT Formula SAE)Mr. Robert Hammond (RIT Formula SAE)

QQuestion Sessionuestion Session

DDesign esign –– Corner LoadsCorner Loads

Strain Gage BasicsStrain Gage BasicsFine wire or metallic foilFine wire or metallic foil

Arranged in grid patternArranged in grid patternMaximize grid to strain parallel Maximize grid to strain parallel to applied loadto applied loadMinimize crossMinimize cross--sectional areasectional area

Reduce affect of shear and Reduce affect of shear and Poisson strainPoisson strain

CarrierCarrierThin backing that connects Thin backing that connects gage to test specimengage to test specimenTransmits any strain from Transmits any strain from specimen to gagespecimen to gage

PurposePurposeConvert mechanical strain to Convert mechanical strain to electrical change in resistanceelectrical change in resistance

DDesign esign –– Corner LoadsCorner LoadsSelection ParametersSelection Parameters

Gage lengthGage length0.125 in 0.125 in –– 0.25 in are common0.25 in are common> 0.25 in> 0.25 in

Quicker and easier installationQuicker and easier installationEasier to handleEasier to handleBetter heat dissipation under cyclic loadingBetter heat dissipation under cyclic loadingLess expensiveLess expensive

Grid Number and LayoutGrid Number and LayoutUni, bi, multiUni, bi, multi--axialaxial

UniUni--axial are low costaxial are low costIdeal for purely axial loadingIdeal for purely axial loading

Planar or StackedPlanar or StackedPlanarPlanar

Increase accuracy and stabilityIncrease accuracy and stabilityResistanceResistance

120120ΩΩ, 350, 350ΩΩ, 1000, 1000ΩΩIncrease resistance, increase sensitivityIncrease resistance, increase sensitivity

DDesign esign –– Corner LoadsCorner Loads

Selection Parameters ContinuedSelection Parameters ContinuedGage Factor (GF)Gage Factor (GF)

Overall sensitivity to strainOverall sensitivity to strainMetal used plays important roleMetal used plays important role

Isoelastic alloys provide high GF (3.6)Isoelastic alloys provide high GF (3.6)Common for dynamic measurementsCommon for dynamic measurementsExtreme temperature sensitivityExtreme temperature sensitivity

Carrier and Adhesive MaterialsCarrier and Adhesive MaterialsCarrier Carrier –– Glass fiber reinforced epoxyGlass fiber reinforced epoxy

Excellent for dynamic loadingExcellent for dynamic loading

Adhesive Adhesive –– epoxyepoxyHigh bond strengthHigh bond strength

OptionsOptionsPrePre--attached lead wire cablesattached lead wire cablesEncapsulationEncapsulation

DDesign esign –– Corner LoadsCorner Loads

Lead Wire ResistanceLead Wire ResistanceAdd offset error and desensitize bridgeAdd offset error and desensitize bridgeWire resistance can be compensated forWire resistance can be compensated forResistance changes to due temperatureResistance changes to due temperature

33--wire connection can eliminate this affectwire connection can eliminate this affect