Campbell Scientific 4WFBS120, 4WFBS350, 4WFBS1K 4 Wire Full Bridge Terminal Input Modules - Manual (Page 13)

4WFBS120, 4WFBS350, 4WFBS1K 4 Wire Full Bridge Terminal Input Modules (TIM)
4.1.3 Quarter Bridge Strain with 3 Wire Program Examples
This section is broken out into CRBasic programs and EDLOG programs.
These programs are only to be used as examples. Besides adding additional
measurement instructions, the programs will need to have the scan and data
storage intervals altered for actual applications. Refer to the datalogger’s
manuals and/or the CRBasic Editor’s help files for detailed information on the
program instructions used as well as additional program examples.
4.1.3.1 CRBasic Programming
Dataloggers that use CRBasic include our CR800, CR850, CR1000, CR3000,
CR5000, and CR9000(X). CRBasic uses the StrainCalc Instruction for
calculating strain from the output of different full bridge configurations:
StrainCalc(Dest,Reps,Source,BrZero,BrConfig,GageFactor,PoissonRatio)
Source is the variable holding the current result from the full bridge
measurement
BrZero is the zero measurement; this parameter uses the results of a previous
full bridge measurement instruction when the gage is at the zero condition
(multiplier=1, offset=0, mV/V) directly.
BRCode for the Bridge Configuration used with the 4WFBS module should be
set to -1 for a quarter bridge strain circuit.
Enter the actual gage factor in the GageFactor parameter.
Enter 0 for the Poisson ratio parameter, which is not used with ¼ Bridge strain
circuits.
Example Program 4.1. CR9000X ¼ bridge Strain with 3 reps
This example program measures the output from the Wheatstone bridge using
the
BrFull instruction. The output from this instruction is input into the
StrainCalc instruction in order to calculate the raw µstrain value. This
program does not use a zero offset reading. See Example Program 4.2 for an
example that performs a zero calibration.
' Program name: STRAIN.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
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
BeginProg 'Program begins here
GF(1) = 2.1 : GF(2) = 2.2 : GF(3) = 2.3 'Initialize gauge factors for Strain( )
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