HygroTrace Moisture Transmitter
19
September 2007
Sensor Dry Down
Following factory calibration, the
HygroTrace
is vacuum
packaged to minimize sensor uptake of ambient moisture during
shipment and storage. Once the unit is installed in the process or
sample system, it is recommended that the user establish a
nominal sample flow of 1 SLM and initiate a manual dry down of
the sensor using the
Sensor Dry Down
option in the
User
Settings Menu
.
The initiation of this dry down cycle depends on the exposure of
the unit to ambient moisture conditions. The criteria for exposure
is detailed below. It is recommended that the heater control be set
to 190°C for 24 hours following initial installation. The dry down
cycle must be manually started and stopped by the user.
General rule of thumb: >72 hours @ <10% RH or
>24 hours @ >40% RH
This sensor-drying procedure can be repeated following
prolonged exposure to ambient moisture conditions. This will
ensure the highest accuracy for moisture measurement.
Note:
When in Dry Down mode, the unit will report a fixed
output of 20.5 mA, the maximum valid measurement.
When returned to normal operation, the output will return
to reporting the actual measurement.
To initiate a manual dry down of the
sensor, select
Sensor Dry Down
in
the
User Settings Menu
. Press
Enter
and the following screen appears:
Press
Enter
to start the
Sensor Dry
Down
(or press
Cancel
to not begin
a sensor dry down cycle) and return
to the previous screen. If you
pressed
Enter
, the
Sensor Dry Down
has begun.
Note:
The sensor will be heated to and remain at 190°C until the
user stops this cycle.
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