Core Process Variable: Specific Gravity, Molecular Weight, Or Relative Density; Core Process Variable And Available Gas Process Variables - Emerson Micro Motion SGM Series Configuration And Use Manual

Orientation and planning
Table 2-1: Terms used in meter setup and measurement
Term
Wobbe index
2.3 Core process variable: Specific gravity,
molecular weight, or relative density
The SGM can operate as a specific gravity meter, a molecular weight meter, or a relative
density meter. This represents the core process variable that gas process data is based on.
Your choice determines the set of process variables that the meter can report, the
methods used to measure and calculate them, and the data that you must supply during
setup and configuration.
The core process variable – specific gravity, molecular weight, or relative density – was
specified as part of the order. However, you can change it during calibration.
Related information
2.3.1

Core process variable and available gas process variables

The gas process variables that the SGM can report are determined by the core process
variable that you select during calibration.
Table 2-2: Core process variable and available process variables
Available process variables
Specific gravity
Molecular weight
Relative density
Base density
Line density
Line compressibility
Base compressibility
Calorific value
Wobbe index
Energy flow
8
Definition or usage
The ratio of the calorific value of a gas to its specific gravity. Measured in volu-
metric units (BTU/SCF, and MJ/SCM).
Core process variable and available gas process variables
Core process variable, gas process variables, and required data
Default measure-
ment unit
Unitless
g/mol
Unitless
g/cm³
g/cm³
Unitless
Unitless
MJ/m³
MJ/m³
MJ/hr
(continued)
Core process variable
Specific gravity Molecular weight
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Micro Motion
Relative density
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Gas Specific Gravity Meters (SGM)