3-12 | Thermox TM 2000 Oxygen Analyzer
RCU wiring
See the “Wiring” section in the Installation Chapter for help on how to
connect wiring between the control unit and the RCU. Once completed,
this wiring allows the software in the control unit to turn on the appro-
priate valves in the RCU during calibration. This includes turning off the
sample gas valve and turning on the appropriate calibration gas valve.
PPM Measurement Suggestions
This section provides advice for those who use the TM2000 in the low
PPM ranges. You can calibrate using percent gases and still operate using
PPM gases; using the sample bypass option can improve response times
for applications where response times are critical.
Use Percent Calibration Gases - You can use percent oxygen calibration gases
to calibrate your system, even if your sample gas is in the low PPM oxy-
gen range. Percent calibration gases are less expensive than PPM calibra-
tion gases, including the pressure regulators on the tanks. In addition, you
don’t lose any calibration accuracy when using percent calibration gases.
Percent calibration gases are less sensitive to hydrocarbons in the cali-
bration tank than are PPM calibration gases. If using a low PPM oxygen
calibration tank, even a few hydrocarbons in the tank can significantly
affect its calibration value as measured by the TM2000. With percent oxygen
calibration gases, the calibration gas value is much less influenced by hydrocar-
bons since there is much more oxygen to offset the effects of the hydrocarbons.
Gas Sample Bypass
A good practice in the measurement of PPM gas concentrations
(when checking calibration, calibrating, or during initial start-up) is
to provide a bypass on the gas sample inlet to the analyzer. This will
improve the response time of your analyzer by purging out the dead
volume in the sample line. The sample bypass is especially helpful
with systems that have a long sample line. See the applicable sections
in the user’s manual for information on the factory-provided sample
bypass option.
Leaks
Ensure that all tubing you connect to the analyzer is leak tight. Since
air contains approximately 209,000 PPM of oxygen, even the slightest
leak in the sample gas line can lead to inaccurate readings. You can
run a vacuum check as described in the Troubleshooting chapter to
check your setup for leaks.
Clean Tubing
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