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8.2 Common Problems
If the moisture.IQ measurement readings seem strange or do not make sense, there may be a problem with the probe or
the process system. Table 12 below contains some of the most common measurement problems.
Symptom
Possible Cause
Accuracy of
Insufficient time for system to
moisture sensor
equilibrate
is questioned.
Dew point at sampling point is
different than the dew point of
the main stream.
Sensor or sensor shield affected
by process contaminants (refer
to Basic GE Sensing Hygrometry
Principles).
Sensor is contaminated with
conductive particles (refer to
Basic GE Sensing Hygrometry
Principles).
Sensor is corroded (refer to
Basic GE Sensing Hygrometry
Principles).
Sensor temperature is greater
than 70°C (158°F).
Stream particles are causing
abrasion.
Screen always
Probe is saturated. Liquid water
reads the wettest
present on sensor surface
(highest))
and/or across electrical
programmed
connections.
moisture
Shorted circuit on
calibration value
sensor.
while displaying
dew/frost point.
Sensor is contaminated with
conductive particles (refer to
Basic GE Sensing Hygrometry
Principles.
Improper cable connection.
moisture.IQ User's Guide
Table 12: Troubleshooting Guide for Common Problems
System Response
Probe reads too wet during
dry down conditions, or too
dry in wet up conditions.
Probe reads too wet or too
dry.
Probe reads too wet or too
dry.
Probe reads high dew
point.
Probe reads too wet or too
dry.
Probe reads too dry.
Probe reads too wet or too
dry
Action
Change the flow rate. A change in dew point indicates
the sample system is not at equilibrium, or there is a
leak. Allow sufficient time for the sample system to
equilibrate and the moisture reading to become steady.
Check for leaks.
Readings may be correct if the sampling point and main
stream do not run under the same process conditions.
Different process conditions cause readings to vary. If
sampling point and main stream conditions are the
same, check sample system pipes, and any pipe
between the sample system and main stream for leaks.
Also, check sample system for adsorbing water
surfaces, such as rubber or plastic tubing, paper-type
filters, or condensed water traps. Remove or replace
contaminating parts with stainless steel parts.
Clean the sensor and the sensor shield as described in
document 916-064, Basic GE Sensing Hygrometry
Principles. Then reinstall sensor.
Clean the sensor and the sensor shield as described in
document 916-064, Basic GE Sensing Hygrometry
Principles. Then reinstall sensor.
Return probe to factory for evaluation.
Return probe to factory for evaluation.
Return probe to factory for evaluation.
Clean the sensor and the sensor shield as described in
document 916-064, Basic GE Sensing Hygrometry
Principles Then reinstall sensor.
Run "dry gas" over sensor surface. If high reading
persists, then probe is probably shorted and should be
returned to the factory for evaluation
Clean the sensor and the sensor shield as described in
document 916-064, Basic GE Sensing Hygrometry
Principles. Then reinstall sensor.
Check the cable connections to both the probe and the
moisture.IQ.
Chapter 8. Troubleshooting
93
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