Re-Calibration Of The Chilled Mirror Reference - Michell Instruments OptiCal User Manual

OPTIDEW
Procedure (using RS232 serial commands)
1. Connect to the instrument using the RS232 connection.
2. Send the following commands, one after the other:
Command Description
st
gofth
abc
The instrument will now be in DCC for 4 minutes – it is important that
the adjustments are only made in this mode. During this time adjust the
potentiometer until the signal level is 150 ±10.
If the instrument comes out of DCC (the status LED will no longer be
illuminated) send the
3. Once adjustment is complete, cycle power to the instrument.
4.2.4

Re-calibration of the Chilled Mirror Reference

As with all high quality measuring instruments, regular re-calibrations of the integral
chilled mirror reference against a standard is recommended. This can only be achieved
by exposure of the sensor to sample gases of known moisture content, while comparing
readings against a calibrated reference instrument traceable to national standards. It
is recommended that the entire instrument is returned to Michell Instruments on an
annual basis for calibration and routine maintenance and service.
The accuracy and integrity of the Optidew reference will highlight any drift in the
accuracy of the controlling %RH probe, which will be seen as a difference between
the set point for %RH and temperature and the values measured by the reference
instrument. When these differences become signifi cant, then a replacement %RH probe
will be required.
22
Stops all continuous output to the serial port
Continuously outputs signal mirror level, between 0 and
1023
Starts a DCC cycle
command again.
abc
OptiCal User's Manual
97079 Issue 9.2, March 2016