5 Purging and calibration
5.1 On-site setup requirements
The SGM is shipped with an empty reference chamber and no calibration factors. The SGM cannot be factory
calibrated. Instead, you must perform calibration in the field using one of two on-site setup procedures. A
setup procedure involves purging and filling the reference chamber with your process gas, then using known
calibration gases.
Related information
Prepare for SGM purging and calibration
Purge and purge-cycle the SGM device
Calibrate the SGM device
Review data for all calibrations
Select the active calibration
5.2 Prepare for SGM purging and calibration
Before you begin these procedures, you must:
• Know the primary process variable that you want to use. In other words, you must know whether the
meter will operate as a specific gravity meter, a molecular weight meter, or a relative density meter.
• Know if you need a two-point or three-point calibration. Most applications require a two-point calibration.
For a few exceptions, a three-point calibration may be required.
• Prepare the calibration gases.
• Know the appropriate control pressure.
• Be able to control sample pressure and vent pressure.
Related information
Three-point calibration
5.2.1 Primary 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. 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 primary process variable — specific gravity, molecular weight, or relative density — needs to be specified
as part of the order. However, you can change the primary process variable during calibration.
Related information
Primary process variable and available gas process variables
Primary process variable, gas process variables, and required data
Configuration and Use Manual Purging and calibration
MMI-20020954 March 2021
Configuration and Use Manual 27
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