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Teledyne API Model 100AH SO
2
Analyzer Instruction Manual, 02417, Rev. D
Sample Flow
The sample flow is computed from the pressure measured upstream of the flow control module.
Since the downstream of the orifice is well within the critical pressure (which is also checked
continuously), it is the upstream pressure of the orifice responsible directly proportional to the
flow through the orifice. Flow variation has little effect on the analyzer reading. Its nominal
value is 650 ± 60 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 up to 5000 mV when a high
concentration of SO
2
is being measured. If the PMT reading is consistently 5000 mV, that
indicates an off-scale reading. Typical readings bounce around, which is normal.
UV Lamp
UV Lamp reading is the measurement voltage from the reference detector preamp board. Typical
value is between 2000 mV and 4000 mV and above 600 mV is acceptable.
Stray Light
Stray Light is the background light of the reaction cell expressed in PPM while sampling zero
gas. It is only an indication of the condition of the optical system such as lenses, UV filter, light
leak, etc.
Dark PMT
The dark current of the PMT is periodically measured to compensate any PMT dark current drift
and offset. Typical value is less than 200 mV.
Dark Lamp
This is the dark current of the UV reference detector which is used to compensate any dark
current drift and offset. This measurement is synchronized to the Dark PMT measurement
period. Typical value is less than 200 mV.
Slope
The coefficient of straight line equation (y = mx + b) determines the calibration of the M100AH.
The slope parameter (m) can be thought of as a gain term which determines the steepness of the
calibration curve. Typical value is 1 ± 0.3.
Offset
The offset parameter (b) compensates for differences in the background signal of the optical
system. Typical value is less than 100 mV.
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