Campbell Scientific CR3000 Micrologger - Manual (Page 169)

Section 7. Installation
169
CRBasic Example 31. FieldCalStrain() Calibration Demonstration
'Program to measure quarter bridge strain gage
'Measurements
Public Raw_mVperV
Public MicroStrain
'Variables that are arguments in the Zero Function
Public Zero_Mode
Public Zero_mVperV
'Variables that are arguments in the Shunt Function
Public Shunt_Mode
Public KnownRes
Public GF_Adj
Public GF_Raw
'----------------------------- Tables ----------------------------
DataTable (CalHist,NewFieldCal,50)
SampleFieldCal
EndTable
'//////////////////////////// PROGRAM ////////////////////////////
BeginProg
'Set Gage Factors
GF_Raw = 2.1
GF_Adj = GF_Raw
'The adj Gage factors are used in the calculation of uStrain
'If a calibration has been done, the following will load the zero or
'Adjusted GF from the Calibration file
LoadFieldCal (True)
Scan (100,mSec,100,0)
'Measure Bridge Resistance
BrFull (Raw_mVperV,1,mV50,1,Vx1,1,2500,True ,True ,0,250,1.0,0)
'Calculate Strain for 1/4 Bridge (1 Active Element)
StrainCalc (microStrain,1,Raw_mVperV,Zero_mVperV,1,GF_Adj,0)
'Steps (1) & (3): Zero Calibration
'Balance bridge and set Zero_Mode = 1 in numeric monitor. Repeat after
'shunt calibration.
FieldCalStrain (10,Raw_mVperV,1,0,Zero_mVperV,Zero_Mode,0,1,10,0 ,microStrain)
'Step (2) Shunt Calibration
'After zero calibration, and with bridge balanced (zeroed), set
'KnownRes = to gage resistance (resistance of gage at rest), then set
'Shunt_Mode = 1. When Shunt_Mode increments to 3, position shunt resistor
'and set KnownRes = shunt resistance, then set Shunt_Mode = 4.
FieldCalStrain (13,MicroStrain,1,GF_Adj,0,Shunt_Mode,KnownRes,1,10,GF_Raw,0)
CallTable CalHist
NextScan
EndProg