Performing Routine Calibrations - GE HumiLab Operator's Manual

Performing routine calibrations

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If you ever accidentally switch the Humilab to the "CAL" mode,
simply shut the power OFF and then ON using the power switch
(on the rear panel) to reset to normal operation.
The unit has been calibrated at the factory. Field calibration is only
required if the measured humidity deviates from the setpoint
humidity by more than 1% RH after one hour.
With the selector switches preset to the proper positions for normal
operation, calibration may be performed as follows:
1. Insert the item(s) to be calibrated into the Humilab humidity
chamber. Run power cables via the top cover to the transmit-
ter.
2. Select the proper RH Setpoint.
When this switch is held up (for higher humidity) or down (for
lower humidity), the digital set point display will scroll toward
the desired set point. First the least significant decade will
change, and then successively more significant decades will
change. Release the switch when the desired humidity is reached.
It may be easier to stop a few counts before the desired reading,
and allow the least significant unit display to move in 0.1%
R.H. steps to the set point.
3. Allow 40 to 60 minutes equilibration time.
The R.H. in the Humilab cavity will gradually move toward the
set point. For the first 20–30 minutes, there will be no
closed-loop feedback. After the loop is controlled, a correction
will be made every 5 minutes.
4. Calibrate as required.
Relative humidity is a function of temperature as well as moisture
content. If you are calibrating a device (such as a humidity trans-
mitter) that generates heat, locate it near the center of the cavity.
This will allow the HumiLab's temperature sensor to quickly
sense the temperature change and correct for it.
Chapter 2 — Operation