Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 154)

Section 7. Installation
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8. Set Mode = 4 to start second part of calibration.
a. Mode = 5 (automatic) during second point calibration.
b. Mode = 6 (automatic) when calibration is complete.
7.8.1.5 FieldCal() Demonstration Programs
FieldCal() has the following calibration options:
• Zero
• Offset
• Two-point slope and offset
• Two-point slope only
• Zero basis (multi-put zero)
These demonstration programs are provided as an aid in becoming familiar with
the FieldCal() features at a test bench without actual sensors. For the purpose of
the demonstration, sensor signals are simulated by the CR800 excitation channel.
To reset tests, use the support software File Control
(p. 431)
menu commands to
delete .cal files, and then send the demonstration program again to the CR800.
Term equivalents are as follows:
"offset" = "y‐ intercept" = "zero"
"multiplier" = "slope" = "gain"
7.8.1.5.1 Zero or Tare (Option 0)
Zero option simply adjusts a sensor's output to zero. It does not affect the
multiplier.
Case: A sensor measures the relative humidity (RH) of air. Multiplier is known to
be stable, but sensor offset drifts and requires regular zeroing in a desiccated
chamber. The following procedure zeros the RH sensor to obtain the calibration
report shown. Use the external keyboard / display or software numeric monitor to
change variable values as directed.
Table 22. Calibration Report for Air RH Sensor
Parameter Argument at Deployment
Argument at 30-Day
Service
mV output 1000 mV 1050 mV
KnownRH (desiccated
chamber) 0 % 0 %
Multiplier 0.05 % / mV 0.05 % / mV
Offset -50 % -52.5 %
RH reading 0 % 0 %