Emerson Micro Motion SGM Configuration And Use Manual page 15

Configuration and Use Manual
MMI-20020954
2.3.2 Primary process variable, gas process variables, and required
data
The gas process variables are calculated from a combination of measured variables, calculated variables,
process data from external devices, and user-specified values. For each process variable that you want the
meter to report, you must be able to supply all required external data and configuration values. Specific
requirements are determined by the primary process variable.
Note
The meter does not measure certain process variables directly. External devices are required for the following
process variables:
• Line pressure
• Gas composition (% CO, % CO2, % H2, % N2)
• Flow rate (mass or volume)
Note
• If you use temperature data from the meter, the data will represent the gas inside the measurement
chamber.
• If you use temperature data from an external device, the data will represent the gas at the location of the
temperature probe.
Table 2-2: Gas measurement when the primary process variable is specific gravity
Process variable to be reported
Specific gravity
Molecular weight
Base density
Line density
NX 19
Line compressibility
NX 19 Mod
Configuration and Use Manual
Process data provided Required process data
by the SGM from external devices
Specific gravity
Specific gravity
Molecular weight
Base compressibility
Temperature data from
(1)
meter (RTD)
External temperature
Base density
Line pressure
Line compressibility
Base compressibility
External temperature
Sample temperature
Line pressure
(1)
(RTD)
% CO2
Specific gravity
% N2
External temperature
Sample temperature
data from meter Line pressure
(1)
(RTD)
% CO2
Specific gravity
% N2
Orientation and planning
March 2021
Required user-
specified values
Molecular weight of air
Base pressure
Base temperature
(2)
Base pressure
Base temperature
(2)
Molecular weight of air
(2)
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