Core process variable and available process variables (continued)Table 2-2:
Available process variables
Default measure-
ment unit
Core process variable
Specific gravity Molecular weight Relative density
Concentration (gas purity) Concentration
(% mass)
✓ ✓ ✓
Net mass flow rate g/sec ✓ ✓ ✓
Net volume flow rate l/sec ✓ ✓ ✓
2.3.2 Core 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 core 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)
• Line temperature (only if you choose to use external temperature rather than temperature
data from the meter)
Tip
You can use temperature data from the meter or from an external device.
• If you use temperature data from the meter, related process variables will represent the gas
inside the measurement chamber.
• If you use temperature data from an external device, related process variables will represent
the gas at the location of the temperature probe.
Gas measurement when the core process variable is specific gravity
Table 2-3:
Process variable to be reported
Process data from the
meter
Process data from ex-
ternal devices User-specified values
Specific gravity Specific gravity
Molecular weight Specific gravity Molecular weight of air
Base density Molecular weight
Base compressibility
Base pressure
Base temperature
Orientation and planning
Configuration and Use Manual 9
To Next Page
Loading...
Need help?
General
