GE Moisture Image 1 Series, Service Manual, Page: 96 / 107

June 2003
A-34 Application of the Hygrometer (900-901D1)
Solids Applications
A. In-Line
Measurements
GE Panametrics moisture probes may be installed in-line to
continuously monitor the drying process of a solid. Install one sensor
at the process system inlet to monitor the moisture content of the
drying gas and install a second sensor at the process system outlet to
monitor the moisture content of the discharged gas. When the two
sensors read the same (or close to the same) dew point, the drying
process is complete. For example, a system of this type has been used
successfully to monitor the drying of photographic film.
If one wishes to measure the absolute moisture content of the solid at
any time during such a process, then an empirical calibration is
required:
1. At a particular set of operating conditions (i.e. flow rate,
temperature and pressure), the hygrometer dew point reading can
be calibrated against solids samples with known moisture
contents.
2. Assuming the operating conditions are relatively constant, the
hygrometer dew point reading can be noted and a solids sample
withdrawn for laboratory analysis.
3. Repeat this procedure until a calibration curve over the desired
moisture content range has been developed.
Once such a curve has been developed, the hygrometer can then be
used to continuously monitor the moisture content of the solid (as
long as operating conditions are relatively constant).