Texas Instruments PGA309 User manual

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

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 2
PGA309 Quick Start

SBOA103C
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

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 4
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.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 5
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.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 6
Span –the amount ofchange innormalized output voltage (inV/V)ofthe
sensoroverthe entirerangeofappliedstimulus.
Offset –the normalizedoutput ofasensor(inV/V)withno applied
stimulus.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 7
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

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 8
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

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 9
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

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 10
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.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 11
SensorOutputvsApplied Stimulus
0.00E+00
5.00E-04
1.00E-03
1.50E-03
2.00E-03
2.50E-03
3.00E-03
3.50E-03
4.00E-03
0 10 20 30 40 50 60 70 80 90 100 110
AppliedStimulus(%)
Sensor output (V/V)
idealspan
span
slope real_sensor 100 real_sensor 0
−
(
)
stim100 stim0 −
( )
3.6710 3− ⋅0−
(
)
100 0−( ) 3.67 10 5−
×
ideal_sensor stim( ) slopestim⋅
ideal_sensor 50( ) 3.67 10 5− ×
( )
50⋅1.835 10 3− ×
PresureNonlinearity real_sensor 50 ideal_sensor 50
−
( )
real_sensor 100 100⋅1.66 10 3−
×1.835 10 3− ×−
( )
3.67 10 3− ×
( )
100⋅4.768−%
The secondorder (quadratic)
nonlinearityversusappliedsignal
given in%ofspan.
Note: Thesereadingswere all
taken at roomtemperature. So,
real_sensor100 isthespan ofthe
sensorat roomtemperature.
Pressure
Nonlinearity

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 12
Pnonlin P() P 4Nonlinearity_pct⋅100⋅P
100
P
100





2
−





⋅+
Span_TCT() SpanTC1T T
room
−
( )
⋅SpanTC2T T
room
−
( )
2
⋅−
Offset_TCT() OffsetTC1T T
room
−
( )
⋅OffsetTC2T T
room
−
( )
2
⋅−
SensorOutputPT,( ) Offsetroom Spanroom Offset_TCT()⋅+ Span Nonlinearity_pct
100 1Span_TCT()+( )⋅





⋅+





The equationsusethe constantsdefinedon thepreviousslides.These
equationsareused inthe generate_emu_settings.xls spreadsheet*to
computethe voltage settingsforthe Sensor-Emulator-EVM.
Sensor OutputEquations
*Availablefordownload at www.ti.com asSBOC065

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 13
For thisquickstart examplethe specificationsbelowandthe examplehardwareconfiguration will beused.
The Sensor-Emulator-EVMwill createanequivalent forthe illustratedRealWorldInputs.
“generate_sim_values.xls
“OffsetandSpan”Tab
PGA309 Absolute
Calibration Example

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 14
Step 1: Will the PGA309
work formysensor?
•Useyoursensor’sspecificationswiththe PGA309
Calculatorsoftwaretool(SLVC073)toseeifthe PGA309
hasthe gainand offsetadjustment rangerequired to
accommodateyoursensor.
•UsethePGA309Calculatorsoftwaretooltoverifythat
yourdesigndoesnot violateanyof themost critical
PGA309 specifications(internalorexternalnodes).

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 15
Enter
information
here. For
example,
enterthe
valuesshown.
Press Compute
Constants and
the resultinggain
settingswill be
displayed here.
Enteryoursensorparametersand yourPGA309
configuration parameterstoget the gainscaling.
If yourdesign
generatesvalues
forgain and offset
that areout ofthe
PGA309’srange,
the softwarewill
flag the problem.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 16
The programselectsvaluestoallow
the GainDACandZeroDACtohave
the maximumadjustablerange. The
Set AdditionalConstraints button isa
waytoforcethefront end gain or
coarseoffset toaconstant. Forthis
example, set the coarseoffsetzeroto
minimizenoise.Click Apply
Constraints and then click Compute
Constants. Inthiscasethe range of
adjustmentforthe ZeroDACis
reduced butisstill adequateto
correct forthesensordrift.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 17
Afterthegainsandoffsetsof the
PGA309 havebeencalculated, press
SimulateDevice tosee if anyinternal
nodesareout of range.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 18
Step 2: Connect the hardware
ExampleofaTypical Engineering Bench SetupUsing theSensorEmulator
ThisdiagramillustratesanexampleofhowtheSensor-Emulator-EVMwouldbeusedinanengineeringbench
setup. ThePGA309 isaprogrammablesensorsignalconditioningchip.The Sensor-Emulator-EVMcan be used
inconjunctionwiththePGA309EVM(bothversions)tofacilitatethe development ofthe PGA309application.

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 19
JumpersetupofPGA309EVM-xx and connections
toPC,power, andthe Sensor-Emulator-EVM

SBOA103C
Jan 2006 PGA309 QuickStart SystemReferenceGuide 20
Required Electrical Connectionsto
Sensor-Emulator-EVM