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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