Chapter 7. Maintenance; Minor Maintenance Of Sensor Optics; Cleaning And Balancing The Sensor Mirror - GE Optica Operator's Manual

Chapter 7. Maintenance

7.1 Minor Maintenance of Sensor Optics

Periodically inspect and maintain the sensor optics as described in this chapter. These procedures can be performed at
any time, but are only necessary when the
required.

7.1.1 Cleaning and Balancing the Sensor Mirror

Under normal conditions, the system is self-checking and self-balancing. However, there are occasions when
particulate matter and water-soluble contaminants reduce sensor mirror reflectance and system accuracy (see
"Contamination" on page 37). Three features of the Optica system allow users to monitor and adjust the mirror:
•
The balance indicator (shown in Figure 44 below) provides a graphic display of how much light is received by
the mirror's photodetector. It is also an indicator of the dew layer thickness. This indicator increases and
decreases in digital steps.
•
The bias screw adjusts the light signal received by the reference photodetector and is used as a "coarse
adjustment."
•
The automatic balance, or
the optical balance between the IR emitters and reference photodetectors.
In operation, the position of the balance indicator will depend on the level of humidity and the sensor used. As the
humidity changes, the chilled mirror system will seek to establish control.
As contaminants deposit on the mirror, the optical balance indicator will increase, as will the dew point readings. The
cycle or manual cleaning and balancing (followed by the
PACER
Note: If the mirror is severely scratch or pitted, you may not be able to balance it. It may be replaced in the field, as
discussed in "Field Replacement of Sensor Mirrors" on page 79. For industrial applications, GE recommends
the solid platinum mirror.
Indicator
Optica™ Operator's Manual
Service
cycle (discussed in "The PACER Cycle" on page 6), electronically fine tunes
PACER
Status
Figure 44: Balance and Status Indicator on Optica Display
indicator appears on the status display, indicating that service is
cycle) will mitigate the contamination.
PACER
Chapter 7. Maintenance
Balance
Indicator
75