GE Moisture Image 1 Series, Service Manual, Page: 86 / 107

June 2003
A-24 Application of the Hygrometer (900-901D1)
A: General Case (cont.)
Complete the following steps to determine the moisture content from
the nomograph:
1. Using a straightedge on the two scales on the right of the figure,
connect the known saturation concentration (PPM
W
) with the
measurement temperature (°C).
2. Read the Henry’s Law constant (K) on the center scale.
3. Using a straightedge, connect above K value with the dew/frost
point, as measured with the GE Panametrics’ hygrometer.
4. Read the moisture content (PPM
W
) where the straight edge
crosses the moisture content scale.
Empirical Determination of K and C
S
If the values of K and C
S
are not known, the GE Panametrics
hygrometer can be used to determine these values. In fact, only one of
the values is required to determine PPM
W
from the nomograph in
Figure A-2 on page A-32. To perform such an analysis, proceed as
follows:
1. Obtain a sample of the test solution with a known water content;
or perform a
Karl Fischer titration on a sample of the test stream
to determine the PPM
W
of water.
Note: The Karl Fischer analysis involves titrating the test sample
against a special Karl Fischer reagent until an endpoint is
reached.
2. Measure the dew point of the known sample with the GE
Panametrics hygrometer.
3. Measure the temperature (°C) of the test solution.
4. Using a straightedge, connect the moisture content (PPM
W
) with
the measured dew point, and read the K value on the center scale.
5. Using a straightedge, connect the above K value with the
measured temperature (°C) of the test solution, and read the
saturation concentration (PPM
W
).
Note: Since the values of K and C
S
vary with temperature, the
hygrometer measurement and the test sample analysis must be
done at the same temperature. If the moisture probe
temperature is expected to vary, the test should be performed
at more than one temperature.