Measuring Dew Points: Pressure Vs. Atmospheric; Moisture Monitor Hints - Sahara -Pak HC-1260 Instruction Manual

INSTRUCTION MANUAL
Sahara Moisture Transmitter
VII. Helpful Information (continued)
B. Measuring Dew Points: Pressure vs. Atmospheric
1. The SMT will measure either pressure or atmospheric dew points. For many
applications, measuring pressure dew point may be more meaningful.
2. To measure pressure dew points, connect the supply line to the inlet of the
sample cell. Slowly open the inlet valve fully and close the outlet valve. The
sample cell should now be pressurized. Slightly open the outlet valve. The
instrument is now measuring pressure dew point.
C. Moisture Monitor Hints
1. The water vapor pressure at the measurement location is the result of not only
the moisture content of the fluid entering the system, but also is due to
desorption of moisture from associated piping, leaks in the piping system, and
moisture trapped in fittings, valves, filters, etc.
2. Whether the sensor is used in situ or in a sampling system, one should
remember that the accuracy and speed of measurement would be dependent
on the dynamics of the fluid and piping system. Response times and
measurement values will depend on the degree of equilibrium reached by the
piping system. Such factors as gas pressure and flow rate, materials of
construction, length and diameter of piping, etc., will to a large degree influence
the moisture levels and response times measured.
3. The most frequent questions associated with the total systems occur when:
a. The response time is very slow.
b. The dew point changes as the temperature changes.
c. The dew point changes as the flow rate changes.
Reference 085
Page 11 of 14
Rev 2
06/06/2013