NS 5.14 Firmware
2–20 4900002262 rev. B 3-23-21
If the display units are correct but the conversion factor is not correct for the
application, a custom conversion factor can be defined using Modbus. To set a
custom conversion fact, first choose the correct display units (based on the
Concentration Unit parameter), and then define the conversion factor for the
associated display units using Modbus. If the Modbus register is set to 0, then
the default conversion factor is used. However, if it is set to a value greater than
0, then that value is used as the conversion factor. Refer to the following
Modbus parameters for more information:
• ppmv ConvFactor 00
• lb ConvFactor 01
• % ConvFactor 02
• mg ConvFactor 03
• ppmw ConvFactor 04
• ppbv ConvFactor 05
• ppbw ConvFactor 06
• grn ConvFactor 07
• user ConvFactor 08
The default conversion factors are defined in Table 2–2 below. These
conversions are only intended as a starting point and are specific to our most
common applications. Furthermore, weight-based units are dependent on the
molecular weight of the background stream, and therefore the conversion
factor must be determined on a case-by-case basis.
If a correct concentration unit option for the display does not exist, then a
custom display unit and conversion can be created using Modbus. To set a
custom display unit, select option 8 for the Concentration Unit parameter.
Next define the ASCII display text and associated conversion factor using
Modbus.
Based on ISO 13443:1996 Natural Gas - Standard reference
conditions are 15
°C, 101.325 kPa and Normal reference
conditions are 0
°C, 101.325 kPa. Default conversion factors are
based on pipeline quality natural gas.
Table 2–2 Default conversion factors
ppmv lb/MMcf % mg/Nm3 ppmw ppbv ppbw grn/ccf
01234567
1.00 0.0473933 0.0001 1.46 1.40 1000.00 1400.00 0.0626285
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