Configure Gas Compressibility Measurement Using The Field Communicator - Emerson Micro Motion SGM Series Configuration And Use Manual

Configure process measurement using the Field Communicator
8.3.2 Configure gas compressibility measurement using the
Field Communicator
Gas compressibility measurement is required for the following process variables: line
density, calorific value, Wobbe index, and energy flow. Gas compressibility measurement
can also be used to calculate compressibility as an independent process variable.
Prerequisites
You must know whether you will measure line compressibility and base compressibility or
you will use fixed values.
If you will use fixed values, you must know the line compressibility and base
compressibility values for your application.
If you will measure compressibility, you must be able to supply gas composition data to
the meter, for the following constituents:
•
•
•
Gas composition must be measured in % by volume.
If you plan to poll an external device for % CO2, % N2, or % H2, ensure that the meter has
the required polling slots available. The meter provides four polling slots, and they may be
already in use. You may need to use a fixed value or digital communications for some
external values. To check the current polling configuration, choose Configure > Manual
Setup > Inputs/Outputs > External Device Polling.
Procedure
1.
2.
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h. (Optional) Choose Configure > Manual Setup > Measurements > Optional Setup
> Gas Measurement > Pressure.
i. Set Pressure Offset to the value required to adjust the pressure data for this
meter.
Tip
A fixed pressure value is not recommended. Gas measurement is very sensitive to pressure,
and a fixed pressure value may produce inaccurate process data.
Carbon dioxide (CO2)
Nitrogen (N2)
Hydrogen (H2) (required only if you plan to measure compressibility according to
SGERG 88)
Configure the meter to use fixed values or to measure compressibility.
a. Choose Service Tools > Maintenance > Modbus Data > Write Modbus Data.
b. To use fixed values, write 0 to Coil 442.
c. To measure compressibility, write 1 to Coil 442.
If you are using fixed values:
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Micro Motion Gas Specific Gravity Meters (SGM)