1072_B
13
June 2020
Troubleshooting
Dry-Down Test
The desiccant tube is used to provide a reliable source of dry air for field testing
the hygrometer’s response. Follow this procedure if the hygrometer indicates
a constant high dew point but you suspect that your process air is dry.
NOTE: Make sure the desiccant is blue in color. If the desiccant is fully pink,
it will not produce dry air and you should purchase a new desiccant tube
before testing.
Remove the yellow caps from the ends of the desiccant tube- save them for re-
use. Connect the sample tubing to one end of the desiccant tube, and the
sample air outlet to the other end. This will create a closed loop of dry air flow
through the hygrometer
and desiccant tube.
Turn on the
hygrometer. In a few
minutes, the reading
should start to drop.
Allow up to an hour for
a -40
reading when
testing model 1072A. If
the hygrometer doesn’t
respond, refer to the
troubleshooting hints
for more information.
Replace the desiccant
tube caps when done.
