a. Write the line compressibility value to Registers 4183-4184, in 32-bit IEEE
floating-point format.
The default value is 0. The range is unrestricted.
b. Write the base compressibility value to Registers 4141-4142, in 32-bit IEEE
floating-point format.
The default value is 1.0. The range is 0.7 to 1.1.
No further actions are required.
3. If you are measuring compressibility, complete the configuration as described in the
following steps.
4. Choose Configure > Manual Setup > Measurements > Optional Setup > Gas
Measurement > Setup Compressibility.
5. Choose Compressibility Method and select the compressibility measurement
method that you want to use or that meets site standards.
Important
• Each compressibility measurement method has associated process limits. If your process
goes outside the valid range, compressibility will be reported as NaN (Not a Number), and
all process variables that require a calculated compressibility value will also be reported as
NaN.
• If you choose AGA NX 19 Mod 3 or SGERG 88, you must set up energy content
measurement. If you choose any other method, energy content measurement is required
only if you want the meter to report calorific value, Wobbe index, or energy flow.
6. If you want to use fixed values for Percent CO2, Percent N2, and/or Percent H2,
Choose Configure > Manual Setup > Measurements > Optional Setup > Gas
Measurement > Setup Compressibility > Gas Composition, and enter the fixed
values, in % by volume.
7. If you want to poll for Percent CO2, Percent N2, and/or Percent H2:
a. Choose Configure > Manual Setup > Inputs/Outputs > External Device Polling.
b. Choose an unused polling slot.
c. Set Poll Control to Poll as Primary or Poll as Secondary.
d. Set External Device Tag to the HART tag of the external measurement device.
e. Set Polled Variable to the appropriate variable.
Related information
Compressibility Method and process limits
Compressibility Method and process limits
Each method for calculating compressibility has specific limits for line temperature, line
pressure, and other process variables. If your process goes outside the valid range,
compressibility will be reported as NaN (Not a Number). All process variables that require
compressibility will also be reported as NaN.
Configure process measurement using the Field Communicator
Configuration and Use Manual 79
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