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Teledyne API Model 200AU NO
X
Analyzer Instruction Manual, 02293, Rev. F
5-11
Sample Flow
The SAMPLE FLOW test function is computed from the pressure measured up-stream of the
sample flow orifice. The pressure down-stream of the orifice is also checked to assure the
assumptions of the equation are valid. This will register variations in flow caused by changes in
atmospheric pressure, but will not detect a plugged sample flow orifice. The nominal value is
1000
±
100 cc/min.
Ozone Flow
The OZONE FLOW test function is directly measured by a solid state flow meter. Variations in
this value indicate variations in ozone flow. The nominal value for ozone flow is 80
±
15 cc/min.
PMT Voltage
The PMT VOLTAGE measures the PMT signal at the output of the preamp board. The
waveform of the PMT voltage can be complex, and vary from near 0 mV when zero gas is in the
reaction cell to 5000 mV when a high concentration of NO
x
is being measured. If the PMT
reading is consistently 5000 mV, that indicates an off-scale reading. Typical readings bounce
around, which is normal.
Normalized PMT Voltage
Like the PMT Voltage TEST function above, the NORMALIZED PMT VOLTAGE measures
the PMT signal at the output of the preamp board. The difference is that several normalization
functions are applied to this signal before it is displayed. The most important is the temperature
and pressure compensation factors. If NORM PMT is used as suggested in the Factory
Calibration Procedure (Section 9.1.6) the M200AU will be correctly calibrated.
PREREACT Voltage
This test measurement is the Pre-reactor voltage. It indicates the most recent reading from the
Pre-reactor circuit. The units are mV and readings up to 1000 are considered normal.
High Voltage Power Supply (HVPS)
The HVPS reading is a measure of the scaled-up HVPS programming voltage. The voltage used
to set the HVPS output is generated on the Preamp board. Its value is between 0 and 1 volt,
corresponding to a voltage of 0 to 1000 volts out of the HVPS. The HVPS front panel TEST
measurement should be greater than 450 volts and will typically be 500-800 V.