Thermalert GP Series Operator’s Manual 41
B.5.5 GPR/GPS Air Purge Collar
The Air Purge Collar accessory is used to keep dust, moisture, airborne parti-
cles, and vapors away from the lens. It can be installed before or after the
mounting bracket. It must be screwed in fully. Air flows into the 1/8” NPT
brass fitting and out the front aperture. Air flow should be a maximum of
0.5-1.5 l/s (1-3 cfm). Clean or “instrument” air is recommended to avoid
contaminants from settling on the lens.
φ 38
(1.5)
φ 63
(2.5)
1/8"
27 NPT
1.5 inch
20 UN-2B
1.5 inch
20 UN-2A
75
(3)
22
(.875)
25
(1)
mm (inches)
Figure B-9: GPR/GPS Air Purge Collar Accessory