Campbell CR800 Series - Fieldcal() Offset (Opt 1) Example

Section 7. Installation
220
'DECLARE VARIABLE FOR FieldCal() CONTROL
Public CalMode
'DECLARE DATA TABLE FOR RETRIEVABLE CALIBRATION RESULTS
DataTable(CalHist,NewFieldCal,200)
SampleFieldCal
EndTable
BeginProg
'LOAD CALIBRATION CONSTANTS FROM FILE CPU:CALHIST.CAL
'Effective after the zero calibration procedure (when variable CalMode = 6)
LoadFieldCal(true)
Scan(100,mSec,0,0)
'SIMULATE SIGNAL THEN MAKE THE MEASUREMENT
'Zero calibration is applied when variable CalMode = 6
ExciteV(Vx1,SimulatedRHSignal,0)
VoltSE(RH,1,mV2500,1,1,0,250,0.05,RHOffset)
'PERFORM A ZERO CALIBRATION.
'Start by setting variable CalMode = 1. Finished when variable CalMode = 6.
'FieldCal(Function, MeasureVar, Reps, MultVar, OffsetVar, Mode, KnownVar, Index, Avg)
FieldCal(0,RH,1,0,RHOffset,CalMode,KnownRH,1,30)
'If there was a calibration, store calibration values into data table CalHist
CallTable(CalHist)
NextScan
EndProg
7.7.11.5.2 FieldCal() Offset (Opt 1) Example
Most CRBasic measurement instructions have a multiplier and offset parameter.
FieldCal() Option 1 adjusts the offset argument such that the output of the sensor
being calibrated is set to the magnitude of the FieldCal() KnownVar parameter.
Subsequent measurements have the same offset added. Option 0 does not affect
the multiplier argument. Option 0 does not affect the multiplier argument.
Example Case: A sensor measures the salinity of water. Multiplier is known to be
stable, but sensor offset drifts and requires regular offset correction using a
standard solution. The following procedure offsets the measurement to obtain the
calibration report shown.