Ametek Thermox TM2000, User Manual

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Installation and Start-Up | 3-5
For calibration gases, the span gas must have an oxygen content that is a
factor-of-ten higher than the zero gas (for example, if the zero gas is 1.0%,
the span gas must be 10% or higher. If the zero gas is .1%, the span gas
must be 1% or higher). We recommend that you use percent calibration
gases, and not PPM calibration gases to calibrate the TM2000 analyzer. See
the PPM Measurement Suggestions section for reasons why you should
use percent calibration gases.
Always use the same flow rate for calibration gases and sample gas to
maintain an accurate TM2000 analyzer. Also, regulate the calibration
gases to provide a delivery pressure that is the same as the sample gas
pressure. This will prevent damage to the sensing cell.
Pressure and flow requirements
In general, the gases flowing into the sensor must be kept at a constant
pressure because the sensing cell is a pressure-sensitive device. Use a
pressure regulator to keep the inlet pressure constant. Pressure fluctua-
tions can lead to inaccurate sensor readings. Also make sure that the inlet
pressure is high enough to maintain the desired flow rates but not over 20
PSIG. The next paragraph describes proper flow rates. In general, use the
lowest pressure possible to maintain the desired flow rate. This will give
you greater control over the flow rate using the flow knob on the sensor.
Maintain a flow rate into the sensor of 0.6 L/min. You can view the sample
flow rate using the Sample Flow Meter on the sensor outlet.
• If not using the sample bypass option, a minimum positive pressure of
1.5 PSIG is required to maintain this 0.6 L/min. flow rate into the sen-
sor.
• If using the sample bypass option, a minimum positive pressure of 6
PSIG is required to maintain both a .6 L/min. flow rate into the sensor
and a 25 L/min. flow rate through the sample bypass.
If you desire a 50 L/min. sample bypass flow rate, you will need 10 PSIG
of positive inlet pressure. You can see the bypass flow rate by using the
Bypass flow meter. If using the sample bypass, you must interactively set
the sample and bypass flow rates until both stabilize (set the sample flow
rate, then set the bypass flow rate).