Table B-2. Modbus Write Registers; Table B-3. System Command Values - Thermo Scientific Omni FTIR Multi Gas CEMS Instruction Manual

Modbus Protocol
Modbus Parameters Supported
B-6 Omni FTIR Multi Gas CEMS Instruction Manual
Table B–2. Modbus Write Registers
Register Number
201
Table B–3. System Command Values
Value Description
0 N/A
1 SAMPLE MODE
2 BLOWBACK MODE
3 BACKGROUND MODE
4 SAVE BACKGROUND
5 BACKGROUND MODE
& SAVE BACKGROUND
6 CHECK ZERO MODE
7 CHECK SPIKE MODE
8 CHECK SPAN MODE
9 CHECK SPAN2 MODE
(N/A)
10 CHECK SPAN3 MODE
(N/A)
Variable
SYSTEM COMMAND
System Status Description
Sample solenoid valve is triggered, only sample flow
is pumped into the gas cell.
System auto blowback is triggered. At the end of
three pulsed blowbacks, the system is switched
back to sample mode.
Sample valve is closed, and instrument zero and
flowback flows are triggered. This mode is
independent of spectrum collection.
The FITR is commanded to collect the spectrum. In
general, this mode should be selected after mode 3
is trigged.
This mode is the combination of mode 3 and mode 4.
After flowing the zero air into the gas cell for five
minutes, the FTIR starts to collect zero air spectrum,
and then saves the spectrum to replace the file
"C:\backgrounds\bkg.spa". At the end, the system is
switched back to sample mode.
In this mode, the system is running just like the
sample mode. At the sample time, the zero air flows
into the probe and is pumped into the gas cell. This
mode is used to test the system zero offset.
The standard gas flows into the probe at a flow rate
of 10% sample flow rate. In general, a trace gas
such as SF6 is used to determine the dilution ratio of
standard gas flow versus the sample flow.
Calibration gas flows into the probe, and is pumped
into the gas cell. This mode is used to check the
system span
This mode is used to perform an extra span check, in
addition to the target gas.
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