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Purge Housing
Replace Desiccant Cartridge
© 2018 Cutting Edge Optronics, Inc.
The Patara optics assembly must be kept at low humidity to protect the SHG
crystal, which is slightly hygroscopic, and to prevent the possibility of
condensation on the laser diode arrays. The Patara housing provides a level of
protection from entry of ambient humidity, but it is not hermetically sealed. When
operating in a high ambient humidity, precautions need to be taken to keep the
interior of the housing dry. The lid of the housing has a port for a desiccant
cartridge, which should be changed when the cartridge indicator is no longer blue.
Also, the housing interior can be purged with clean, dry air using the valve on the
rear of the housing. The inlet line is the stemmed valve and is opened and closed
by rotating the knob on the valve end. Please contact Northrop Grumman before
attempting this procedure.
CAUTION.
The clean dry air input line must be on a pressure regulator and the line
must be filtered.
The desiccant cartridge shown in Figure 5-1 removes excess moisture from inside
the laser head. It is located on the lid of the Patara laser head. The desiccant
cartridge must be replaced regularly, so it should be checked at least weekly for
exhaustion.
Exhaustion is indicated by a change in the color of the indicator paper in the top
of the cartridge. While any sector of the indicator paper in the cartridge top
remains blue, the cartridge can still absorb water. When all three sectors of the
indicator paper turn completely white or light pink, the module has absorbed all
the water it can and must be replaced. Replacement frequency varies with the
humidity in the operating environment and if the laser head is opened.
If the desiccant cartridges are exhausted in a short time frame (e.g., two weeks)
without the laser head having been opened, contact a Northrop Grumman field
service engineer.
41
Chapter Five: Maintenance
Patara I and II Laser User Manual
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