Process Pressure; Actively Measuring Process Pressure; Manually Entering Pressure; Measuring At A Different Pressure - GE Optica Operator's Manual

Chapter 3. Operation

3.6 Process Pressure

The Optica provides several ways of measuring or specifying sample gas pressure (needed for pressurized humidity
measurements). You can do one of the following:
•
Actively measure the pressure at the dew point sensor
•
Manually enter the pressure, if it is known and stable
•
"Sample-off" a high-pressure gas sample for measurement at a lower pressure (usually atmospheric) and let the
Optica calculate dew point at the process pressure.
a sensor with a maximum pressure rating of 300 psi cannot be subjected to a process pressure of
For example:
500 psi. A sampling system can be arranged to allow the measurement to be made at atmospheric pressure. The
Optica can then calculate and display the dew point at the process pressure (see "Scenario 2: Measurement
Requiring the Process Pressure Feature" on page 32).

3.6.1 Actively Measuring Process Pressure

Use this method when the process pressure is within the specifications of the dew point sensor and can be measured
directly. In the Pressure Input menu, set the Pressure Input to V or I as appropriate for the pressure sensor. Set the
Process Pressure Status to Disabled.
Note: The pressure measured by the pressure sensor will be used to compute the vapor pressure.

3.6.2 Manually Entering Pressure

Use this method when the process pressure is a known and fixed value, and will not be actively measured. In the
Pressure Input menu, set the Pressure Input to Use Default. Enter the pressure into the Default field. Set the Process
Pressure Status to Disabled.
Note: The default pressure entered will be used to compute the vapor pressure.

3.6.3 Measuring at a Different Pressure

Use this method when the humidity must be measured at a pressure that is lower or higher than the process pressure,
but the reported value must represent the humidity at the process pressure. "Scenario 2: Measurement Requiring the
Process Pressure Feature" on page 32 gives examples of programming the Optica for this situation.
Note: The process pressure is entered manually and the humidity sensor pressure may be measured or manually
entered.
Examples of the use of the Process Pressure menu are shown in the following sections.
30 Optica™ Operator's Manual