Campbell CR800 Series, Operator'S Manual

Page: 222 / 598

Section 7. Installation
222
FieldCal() Offset
'This program example demonstrates the use of FieldCal() in calculating and applying an
'offset calibration. An offset calibration compares the signal magnitude of a sensor to a
'known standard and calculates an offset to adjust the sensor output to the known value.
'The offset is then used to adjust subsequent measurements.
'This program demonstrates the offset calibration with the following procedure:
' -- Simulate a signal from a salinity 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 the salinity 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 calibration routine by setting variable CalMode = 1. When
'CalMode = 6 (will occur automatically after 10 measurements), the routine is complete.
'Note the new value in variable SalinityOffset. Now enter the following millivolt value as
'the simulated sensor signal and note how the new offset is added to the measurement:
' SimulatedSalinitySignal = 1345
'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 SimulatedSalinitySignal = 1350 'mg/l
'DECLARE CALIBRATION STANDARD VARIABLE AND SET MAGNITUDE
Public KnownSalinity = 30 'mg/l
'DECLARE MEASUREMENT RESULT VARIABLE.
Public Salinity
'DECLARE OFFSET RESULT VARIABLE
Public SalinityOffset
'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)