Field Replacement Of Sensor Mirrors - GE Optica Operator's Manual

7.1.2 Procedure for Cleaning and Balancing the Sensor Mirror (cont.)
When a stable dew or frost layer is attained, you will see the word
the correct dew/frost point and a stable dew or frost layer has been established. When the Optica is exposed to typical
room humidity, this process takes 5-6 minutes. For very dry conditions, the unit may not display
hours. However, the
PACER
before it can display
Control
8. If you see the word

7.2 Field Replacement of Sensor Mirrors

One advantage of using a GE Measurement & Control chilled mirror dew point sensor is that the mirror is
user-replaceable. The sensor does not have to be returned to the factory for replacement of the reflective surface, unless
that is desired.
A mirror may require replacement for any of the following reasons:
•
The mirror is constructed of silver/rhodium plated copper. Copper provides excellent thermal conductivity to
the platinum thermometer. However, some gas constituents, such as sulfur dioxide (SO
copper and eventually pit the surface or form a copper sulfate coating.
•
The reflective surface may be gradually abraded by sharp dirt particles in the gas being measured.
•
The mirror surface may be accidentally scratched or gouged during use or cleaning.
If the sensor mirror has reacted with a corrosive material in the gas sample, such as an acid or sulfur compound, it
should be replaced with a solid platinum mirror to remove any possibility of copper corrosion.
In extreme cases, a solid platinum mirror can make possible a successful application of chilled mirror technology. For
example, measurements in tobacco factories and malting houses have drastically improved after this change, since both
locations have sample gas constituents that attack copper.
Optica™ Operator's Manual
indicator will go out. The sensor must first accumulate a dew or frost layer on the mirror
.
displayed in the lower left, repeat steps 1-7.
Service
in the lower left. The Optica is now reading
Control
Chapter 7. Maintenance
for several
Control
) may react with the
2
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