GD10P User Manual Page 27 of 44 850-811250-Rev.06b
In some environments with excessive heat and/or vibration we have noticed that a higher
percentage of the detectors develop an offset outside the specified tolerances. These detectors
should normally be returned to the factory for service. An alternative is to do this re-zeroing on
site with a dedicated hand held terminal, or HART® communicator.
Note that “on site” does not mean “in service”. Before concluding that re-zero is
necessary, proper cleaning of the detector should be done (even an invisible layer of
oil on the lens or mirror can have negative impact on the zero-point reading). Then,
before re-zeroing is conducted, the detector should be removed from the system and
moved to a controlled environment in a workshop
6.4.1 Test of zero-point in the workshop
Prior to conducting a re-zero, a controlled checking of the zero level should be done with a
sample flow housing and nitrogen test gas (clean instrument air may be used if nitrogen is
unavailable).
1) Clean the sensor optics again, both mirror and lens.
2) Attach a Sample Flow housing (P/N 499-810874)
3) Connect the power supply and HART® terminal
4) Switch on power and wait approx. 2 minutes until the output has stabilized
5) Apply nitrogen gas to the Sample Flow housing
6) Read current loop output
7) If output is outside specification, then a re-zero may be applicable
6.4.2 Re-zeroing with HART® communicator
See section 5.2.4.10.
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