GE Optica, Operator'S Manual

Page: 50 / 150

January 2006
3-6 Operation
Scenario 2: Measurement
Requiring the Process
Pressure Feature
Process pressure is 500 psi, above the measurement range of a typical
GE Infrastructure Sensing chilled mirror sensor. A flow meter is
installed upstream of the sensor cavity to expand the gas to be within
the measurable range of the dew point sensor. Since we wish to
measure the dew point of the process gas and dew point is pressure
dependent, an accurate dew point measurement at the process
pressure requires accommodating for the expansion to the sensor
cavity pressure by using the Optica’s Process Pressure feature (see
Figure 3-6 below).
Figure 3-6: Measurement Scenario 2
Measuring Vapor Pressure
Without a Pressure Sensor
To measure vapor pressure without a pressure sensor, make the
following entries in the Pressure input menu section for this example:
•
Input: Use default
•
Units: psia
•
Default: 14.7 (the pressure at the dew point sensor)
In addition, to accommodate the pressure expansion, the following
entries are required in the Process section:
•
Status: enabled
•
Pressure: 500 (specify the process pressure with the same units
as the default pressure specified above)