Teledyne 9110AH - Nitrogen oxides analyzer - Manual (Page 34)

TELEDYNE Model 9110AH NO
X
Analyzer Operator Manual, 01620, Rev. F
4-2
In the NO/ NO
x
switching mode the Analyzer samples the gas stream and measures [NO]
concentration by digitizing the signal from the Analyzer's photomultiplier tube (PMT). The
concentration is measured and stored internally. The valve is then switched, routing the sample
gas through the converter, the signal measured is the NO
x
concentration which is also stored in
the computer.
The [NO
2
] component is calculated by subtracting [NO
x
] - [NO] = [NO
2
] using the built-in
computer. The three results [NO], [NO
x
], and [NO
2
] are then further processed and stored by
the computer yielding several instantaneous and long term averages for all three components.
Periodically, the AutoZero valve switches allowing the analyzer to read zero background. The
AutoZero readings are subtracted from all of the other readings. This improves zero baseline
stability.