Scenario 2: Measurement Requiring The Process Pressure Feature - GE Optica Operator's Manual

Chapter 3. Operation

3.6.6 Scenario 2: Measurement Requiring the Process Pressure Feature

Process pressure is 500 psi, above the measurement range of a typical GE chilled mirror sensor. A flowmeter 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 the expansion to the sensor cavity pressure by using the
Optica's Process Pressure feature (see Figure 27 below).
3.6.6a 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)
32
Process Pressure (P ) = 500 psi
1
e
1
dew
1
Sensor
Flowmeter
Figure 27: Measurement Scenario 2
e = Process Vapor Pressure
1
Tdew = Process Dew Point
1
e = Vapor Pressure at Sensor
2
Tdew = Dew Point at Sensor
2
Optional
Pressure
Sensor
Optica™ Operator's Manual