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Model 200AU-NOy Option Manual Addendum
3.0 The M501Y NOy Converter
3.1 Principle of Operation
The API Model 200AU with NOy Option is designed to measure the concentration of NO, NO2, and
other compounds that are too unstable to be measured when taken in through the normal ambient air
sample inlet system. Please refer to Section 4 of the M200AU manual supplied with this system for a
general discussion of the operation of a NOx analyzer. The suite of compounds known collectively as
NOy is composed of roughly 30 compounds. There is some disagreement over whether certain
compounds should be on the list. The NOy measurement is generally done in conjunction with a
standard NOx measurement, with the difference between the two being the concentration of the
unstable compounds, sometimes referred to as NOz.
The system is composed of 3 modules:
• The M200AU, without a moly converter
• A Bypass pump chassis containing:
• Bypass pump
• Flow control
• Sample filtration
• Moly temperature control
• Pneumatic provisions for calibration
• An externally mounted molybdenum converter
The M200AU w/NOy Option system allows the converter to be mounted at the sample inlet point.
This configuration provides minimal time delay between the sample inlet port and the remotely
mounted molybdenum converter. Minimizing the transit time between the sample inlet and converter
enables the conversion of labile components of NOy. The equation for the conversion is:
315
o
C
3 NO
Y
+ Mo ---> 3 NO + MoO
3
02808 Rev. E Page 13