Texas Instruments PGA309 User manual

PGA309
Quick Start SystemReference
Guide
byArt Kay
High-Precision Linear Products
SBOA103C
Jan 2006

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Jan 2006 PGA309 QuickStart SystemReferenceGuide 2
PGA309 Quick Start

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Jan 2006 PGA309 QuickStart SystemReferenceGuide 3
RequiredEquipment……………………………………………………..………4
Definitionofsensorspecifications………………………………………………5-12
PGA309 AbsoluteCalibration Example..……….………………………………13
Step 1:Willthe PGA309workforyourapplication?..…..………………14-17
Step 2:Setup hardware……………………………………………..…..…18-21
Step 3:ConfigurePGA309forinitial scaling.……………………………..22-31
Step 4:ConfigureSensor-Emulator-EVMtoemulate
sensor……………………………………………………...………….…..…32-38
Step 5:Usethe Calibration Spreadsheet toperformthe calibration…39-59
PGA309 RatiometricCalibrationExample…………………………………..…60-86
PGA309 WithOutput Scaling Example………………………………………...87-95
PGA309 InThree-WireMode …………………………………………………..96-100
PGA309 Quick StartContents

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Required itemsforQuick Start
Hardware
•PGA309EVM –Thisisan evaluationkit that allowsyou tocommunicatewithandinterfacetothe PGA309. It
containsaPCInterfaceBoardand aSensorInterfaceBoardcombined withaPGA309 andEEPROM.
•Sensor-Emulator-EVM –Thisisan evaluationkit that usesrotaryswitchesand trimpotentiometersto
generatevoltage excited bridge sensoroutputsignalsand temperaturesensoroutput signals.
•+/-12Vsupply– Anylownoisedcsupplyforthe sensoremulator.
•PrecisionDVM– Anyfiveorsixdigit meterthat can readintomicrovolts(e.g., HP3458, HP34401).
•SlottedJeweler’sScrewdriver –Thebest tooltoquicklyadjust the potentiometer.
Software
•PGA309DK BoardInterface –Thissoftwareisused tocommunicatewiththe PGA309EVM. See
http://focus.ti.com/docs/toolsw/folders/print/pga309evm-eu.html undersupport softwareforfree download.
•PGA309 Calculator –Thissoftwareisused todo initialgainscaling andverifythat thedesign doesnot violateany
PGA309 specifications. SoftwareisbundledwithPGA309DKBoardInterfacesoftware.
•PGA309 CalibrationSpreadsheet– ThisspreadsheetusesPGA309 / Sensorreadingsovertemperatureand at
different appliedstimuluslevelstogeneratethecalibrationtableused tocorrect forthesensorerrors. Softwareis
bundled withPGA309DKBoardInterfacesoftware.
•Generate_Emulator_Values.xls –Thisspreadsheet translatessensorspecificationsintovoltage settingsforthe
Sensor-Emulator-EVM. See http://focus.ti.com/docs/toolsw/folders/print/sensor-emulator-evm.html undersupport
softwareforfree download.

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Specifications
Thereareseveralkeyspecificationsthatareusedthroughout ourliterature.
The mathematical definitionsarelistedbelow.
•Offset– thenormalized outputof asensor(in V/V)withno applied stimulus.
•OffsetTC1 –The lineardrift ofthe sensors’offset given in%of span/oC.
•NonlinOffsetDrift –The second order(quadratic)drift oftheoffset. This
coefficientisin %ofspan at roomtemperature.
•OffsetTC2 –The secondorder(quadratic)drift of theoffset.This
coefficientisin %ofspan/oC2at roomtemperature.
•Span – the amountofchange in normalized output voltage(inV/V) ofthe
sensoroverthe entirerangeofappliedstimulus.
•SpanTC1 –The lineardriftof the sensors’span given in %ofspan/oC.
•NonlinSpanDrift –The secondorder(quadratic)driftof the offset. This
coefficientisin %ofspan at roomtemperature.
•SpanTC2 –The second order(quadratic)drift ofthespan.Thiscoefficient
isin %of span/oC2at roomtemperature.
•PressureNonlinearity –The second order(quadratic)nonlinearityversus
applied signalgivenin%of span.

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Span –the amount ofchange innormalized output voltage (inV/V)ofthe
sensoroverthe entirerangeofappliedstimulus.
Offset –the normalizedoutput ofasensor(inV/V)withno applied
stimulus.

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OffsetTC1 Offset3Offset1
−
(
)
Span2T3T1 −
( )
⋅
OffsetTC1 2.963 10 6−
×1.624−10 4− ×
( )
−




3.673 10 3− ×85 40−( )−[ ]⋅3.602 10 4−
×%of span/oC
BridgeSensitivityvsTemp
-5.0E-04
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
3.0E-03
3.5E-03
4.0E-03
-50 0 50 100 150
Temp,degC
Kbridge,V/V
offset
span
(T2,Span2)
(22.5C, 3.67E-3)
(T3,Offset3)
(85C, 2.96E-6)
(T2,Offset2)
(22.5C,1.02E-3)
(T1,Offset1)
(-40C,-1.62E-3)
Linear end pointfitisused to
determine the linear drift.
The linear driftof the
sensor’soffset given in
%of span/oC.
OffsetTC1

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NonLinOffsetDrift
Offset2
Offset1Offset3 +
(
)
2
−





Span2
NonLinOffsetDrift
1.02310 4− ⋅1.624−10 4−
⋅
( )
2.96310 6− ⋅
( )
+




2
−
3.673 10 3− ×4.956 10 2−
×% ofspan
OffsetTC2 NonLinOffsetDrift
T3T1 −
( )
2





2
4.956 10 2− ×
85 40−( )−[ ]
2





21.269 10 5−
×% ofspan/oC2
BridgeSensitivityvsTemp
-5.0E-04
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
3.0E-03
3.5E-03
4.0E-03
-50 0 50 100 150
Temp,degC
Kbridge, V/V
offset
span
OffsetTC2:
The secondorder (quadratic)drift of
the offset. Thiscoefficient isin %of
span/oC2at roomtemperature.
NonlinOffsetDrift:
The secondorder (quadratic)drift
of the offset. Thiscoefficient isin
%ofspanat roomtemperature.
NonlinOffsetDrift
OffsetTC2

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BridgeSensitivityvsTemp
-5.0E-04
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
3.0E-03
3.5E-03
4.0E-03
-50 0 50 100 150
Temp, degC
Kbridge, V/V
offset
span
SpanTC1 Span3Span1
−
(
)
Span2T3T1 −
( )
⋅
SpanTC1 3.728410 3−
⋅3.441210 3− ⋅−
( )
3.6734 10 3− ×85 40−( )−[ ]⋅6.255 10 4−
×%of span/oC
The linear driftof the
sensors’span given
in%of span/oC.
SpanTC1

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NonLinSpanDrift
Span2
Span1Span3 +
( )
2
−





Span2
NonLinSpanDrift
3.6734 10 3− ×3.441210 3−
⋅
( )
3.728410 3− ⋅
( )
+




2
−
3.6734 10 3− ×2.412 10 2−
×% ofspan
SpanTC2 NonLinSpanDrift
T3T1 −
( )
2






2
2.412 10 2− ×
85 40−( )−[ ]
2





26.175 10 6−
×% ofspan/oC2
BridgeSensitivityvsTemp
-5.0E-04
0.0E+00
5.0E-04
1.0E-03
1.5E-03
2.0E-03
2.5E-03
3.0E-03
3.5E-03
4.0E-03
-50 0 50 100 150
Temp,degC
Kbridge,V/V
offset
span
(T3,Span3)
(85C,3.73E-3)
(T1, Span1)
(-40C, 3.44E-3) (T2, Span2)
(22.5C, 3.67E-3)
The nonlinear coefficientassumes T2is
equal distantt oT1 and T3.Thusthe
vertexoftheparabolawill beat T2.
NonlinSpanDrift:
The secondorder (quadratic)drift of
the offset. Thiscoefficient isin %of
spanat roomtemperature.
NonlinSpanDrift
SpanTC2
SpanTC2:
The secondorder (quadratic)drift of
the span. Thiscoefficientisin %of
span/oC2at roomtemperature.