Emerson Micro Motion SGM Series - Page 73

• Hydrogen (H2)
Gas composition must be measured in % by volume.
If you plan to measure energy flow, you must be able to supply flow data to the meter. You
have the following options:
• If you are using an external volume flow device, Volume Flow (External) and Mass
Flow (Calculated) are available.
• If you are using an external mass flow device, Mass Flow (External) and Volume Flow
(Calculated) are available.
Tip
In either case, you can measure energy flow in either mass units or volume units. The meter
automatically selects the appropriate process variable.
If you plan to poll an external device for any of these, ensure that the meter has the
required polling slots available. The meter provides four polling slots, and they may be
already in use. You may need to use a fixed value or digital communications for some
external values. To check the current polling configuration, choose Device Tools >
Configuration > Polled Variables. If you are already polling for one of these, you can use the
existing polled data.
Procedure
1. Choose Device Tools > Configuration > Process Measurement > Calorific Value/BTU/
Wobbe Index/Energy Flow.
2. Set Calorific Value Units to the unit to be used to measure energy content.
3. Set % CO Source to the method you will use to supply % CO data, and perform the
required setup.
Option
Description Setup
Polling The meter polls an external de-
vice for % CO data.
a. Set % CO Source to Poll for External Value.
b. Set Polling Slot to an available slot.
c. Set Polling Control to Poll as Primary or Poll as Secondary.
d. Set External Device Tag to the HART tag of the % CO meas-
urement device.
Digital communica-
tions
A host writes % CO data to the
meter at appropriate intervals.
a. Set % CO Source to Fixed Value or Digital Communications.
b. Perform the necessary host programming and communica-
tions setup to write % CO data to the meter at appropriate
intervals.
Fixed value The configured fixed value is
used.
a. Set % CO Source to Fixed Value or Digital Communications.
b. Set % CO (Fixed) to the desired value, in % by volume.
4. Set % CO2 Source to the method you will use to supply % CO2 data, and perform the
required setup.
Configure process measurement using ProLink III
Configuration and Use Manual 65