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.
Table 8-1: Specific gravity and molecular weight meters: Compressibility Method and valid ranges for
process variables
Compressibility
Method
Valid range
Temperature Pressure Specific
gravity
% CO2 % N2 % H2
AGA NX-19 −40 to
+115.556 °C
1.01325 to
345.751 BarA
0.55 to 1 0–15% 0–15% 0–15%
AGA NX-19 Mod −40 to
+115.556 °C
0 to 137.9
BarA
0.554 to 0.75 0–15% 0–15% N/A
AGA NX-19 Mod 3 0 to 30 °C 0 to 80 BarA 0.554 to
0.691
0–2.50% 0–7% 0–4%
Configure process measurement using a field communicator Configuration and Use Manual
March 2021 MMI-20020954
72 Micro Motion Gas Specific Gravity Meters (SGM)
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