Campbell CR800 Series, Operator'S Manual

Page: 227 / 598

Section 7. Installation
227
FieldCal() Multiplier
'This program example demonstrates the use of FieldCal() in calculating and applying a
'multiplier only calibration. A multiplier calibration compares the signal magnitude of a
'sensor to known standards. The calculated multiplier scales the reported magnitude of the
'sensor to a value consistent with the linear relationship that intersects known points
'sequentially entered in to the FieldCal() KnownVar parameter. Subsequent measurements are
'scaled by the multiplier.
'This program demonstrates the multiplier calibration with the following procedure:
' -- Simulate a signal from a water content sensor.
' -- Measure the 'sensor' signal.
' -- Calculate and apply an offset.
'
'You can set up the simulation by loading this program into the CR800 and interconnecting
'the following terminals with a jumper wire to simulate a water content sensor signal as
'follows:
' Vx1 --- SE 1
'For the simulation, the value of the calibration standard and the initial 'sensor' signal
'are set automatically. Start the multiplier routine by setting variable CalMode = 1. When
'CalMode = 6 (occurs automatically after 10 measurements), the routine is complete. Note the
'new value in variable WCMultiplier. Now enter a new value in the simulated sensor signal
'as follows and note how the new multiplier scales the measurement:
' SimulatedWaterContentSignal = 350
'NOTE: This program places a .cal file on the CPU: drive of the CR800. The .cal file must
'be erased to reset the demonstration.
'DECLARE SIMULATED SIGNAL VARIABLE AND SET INITIAL MAGNITUDE
Public SimulatedWaterContentSignal = 175 'mV, second setting is 700 mV
'DECLARE CALIBRATION STANDARD VARIABLE AND SET MAGNITUDE
Public KnownWC = 10 '% by Volume, second setting is 35%
'DECLARE MEASUREMENT RESULT VARIABLE.
Public WC
'DECLARE MULTIPLIER RESULT VARIABLE AND SET INITIAL MAGNITUDE
Public WCMultiplier = 1
'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
'Multiplier calibration is applied when variable CalMode = 6
ExciteV( Vx1,SimulatedWaterContentSignal,0)
VoltSE (WC,1,mV2500,1,1,0,250,WCMultiplier,0)