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4180, 4181
Technical Guide
use a temperature-controlled aperture, these steps may be applicable to your process. If you do not
use a temperature-controlled aperture, these steps are not applicable to your process.
Frost Control
The 4180 will form frost on the target at temperatures below the dew point. Thus, during calibration at
low temperatures, the Product requires that the surface of the target be purged with clean, dry air.
Accomplish this with the purge provided on the 4180 or with a chamber.
Humidity-Controlled Chamber
The humidity-controlled chamber is a chamber built that fits snugly against the front of the 4180 face
plate on one side and the radiometer fits snugly into the other side. Clean, dry, filtered shop air is
passed through the chamber at a rate sufficient to keep the target from icing. A humidity sensor and
readout are used to monitor the humidity in the chamber and ensure the chamber stays below the frost
point. Figure
10
shows the location of the humidity chamber in front of the 4180 portion of the test
station.
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