Campbell Scientific 4WFBS120, 4WFBS350, 4WFBS1K 4 Wire Full Bridge Terminal Input Modules - Manual (Page 40)

4WFBS120, 4WFBS350, 4WFBS1K 4 Wire Full Bridge Terminal Input Modules (TIM)
In some applications a Dummy or inactive gauge is used in place of the
Dummy resistor (See Section 4.3.1 Quarter Bridge Strain with Dummy Gauge
Wiring Setup). The scheme and underlying equations are the same for this type
of circuit. The only difference is that you do not use the gold plated shunt
receptacles on the 4WFBS module to access the internal matching resistor, as
this resistor is not used.
When performing a shunt calibration, it is usually preferable to use a resistor
that will simulate a strain level within the range between 500 and 1000 uStrain.
When carrying out both a Zero and a Shunt calibration, always
do a zero calibration after the Shunt calibration is complete to
insure that the zero µstrain reading is calculated using the
adjusted gauge factor. NOTE
4.4.2.3 Example Programs for Shunt Calibration of 3-Wire, ¼ Bridge Strain Circuits
Example Program 4.8. CR9000X with Zero and Shunt Calibration
This example program starts out with Example Program 4.2 and adds
instructions to perform a Shunt calibration. Added instructions are highlighted.
A FieldCalStrain instruction takes care of the underlying math for the Shunt
Calibration. Use the Calibration Wizard utility supplied with CSI’s software to
simplify the Shunt Calibration process.
When carrying out both a Zero and a Shunt calibration, always
do a zero calibration after the Shunt calibration is complete to
insure that the zero µstrain reading is calculated using the
adjusted gauge factor. NOTE
Example Program 4.7. CR9000X ¼ Bridge Strain with zero offset andShunt
Calibration
' Program name: StrainSh.C9X
Public StrainMvperV(3) : Units StrainMvperV = mV_per_V 'Raw Strain dimensioned source
Public Strain(3) : Units Strain = uStrain ‘ uStrain dimensioned source
Public GF(3) 'Dimensioned gauge factor
Public ZeromV_V(3), ZeroStrain(3) ZReps, ZIndex, ModeVar
Public GF_Adjusted(3), KnownRs(3), ShuntReps, ShuntIndex,ModeShunt
Dim I
DataTable
(STRAIN,True,-1) 'Trigger, auto size
DataInterval (0,0,0,100) 'Synchronous, 100 lapses, autosize
CardOut (0,-1) 'PC card , size Auto
Sample (3,Strain(),IEEE4) '3 Reps, uStrain, Resolution
Sample (3,StrainMvperV(),IEEE4) ‘3Reps,Stain mVolt/Volt, Resolution
EndTable 'End of table STRAIN
DataTable (Calib, NewFieldCal ,10) ‘Table for calibration factors from zeroing
SampleFieldCal ‘User should collect these to his computer
EndTable ‘for future reference
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