Teledyne API Model 200AH NOX Analyzer Instruction Manual, 06492, Rev. G2
4-2
concentration is measured and stored internally. The valve is then switched, routing the sample
gas through the converter, the signal measured is the NOX concentration which is also stored in
the computer.
The [NO2] component is calculated by subtracting [NOX] - [NO] = [NO2] using the built-in
computer. The three results [NO], [NOX], and [NO2] 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.
4.1.2. Oxygen Measurement (Option)
The Oxygen Sensor used in M200AH utilizes the paramagnetic susceptibility of oxygen, a
physical property that distinguishes oxygen from most other common gases.
The sensor incorporates two nitrogen-filled glass spheres mounted on a strong rare metal taut-
band suspension. This assembly is suspended in a symmetrical non-uniform magnetic field.
When the surrounding gas contains paramagnetic oxygen, the glass spheres are pushed further
away from the strongest part of the magnetic field. The strength of the torque acting on the
suspension is proportional to the oxygen content of the surrounding gases.