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Model 200AU-NOy Option Manual Addendum
4.0 CALIBRATION AND ZERO/SPAN CHECKS
Unlike most NOx analyzers, the M200AU with the NOy option does not have a sample inlet port on
the rear panel; therefore zero/span calibration is different than a normal NOx instrument.
Follow the steps in Section 7 of the M200AU manual to:
a. Enter the expected NO and NOx span gas concentrations in the M200AU.
b. Do the zero calibration procedure covered in Section 7.1.
c. Do the span calibration procedure covered in Section 7.1.
The M200AU / NOy can be calibrated only with zero/span gas entering near the remote
sample port on the pole. There is a fitting on the Bypass Pump Module to input the
calibration gas to this port via a third Teflon hose that is part of the umbilical.
Calibration gas delivered in this manner must be under a small amount of pressure to
overcome the resistance of the hose (pushed up the hose). The calibrator or gas
bottle output must be directly connected to the calibration gas inlet on the back of the
Bypass Pump module - there must be no other venting of the zero or span gas to
atmosphere.
The system contains no provision for calibration gas shutoff or flow control, therefore
the calibration gas system must provide for both. Flow requirements are 1.1 LPM for
NO, 1.1 LPM for NOx and 1 LPM for the M200AU. Calibration gas flow must be in
sufficient excess (~4 LPM) to prevent any ambient air from entering the sample port on
the pole.
The maximum 50 ft length of tubing between the Bypass Pump Module and the remote moly converter
has been proven to generate too much backpressure for some brands of calibrators. Experience to date
is that while NO calibration is correct, GPT can be incorrect due to errors in dilution of the ozone.
Although the M200AU manual shows several ways to check and adjust the calibration of the
M200AU, there is only one way to calibrate or check the calibration of the M200AU/ NOy. This is
calibration with zero gas coming in the sample port - covered in Section 7.1 of the M200AU manual.
We strongly recommend that SPAN CALIBRATION be done with NO span gas. SPAN CHECKS can
be done with either NO only, NO2 only or a mixture of NO and NO2 (GPT).
Zero air used for all calibration procedures, including GPT, should have <1 ppt NO and NO2, less than
1 ppt of major interferents such as SO2, NH3, hydrocarbons and a dew point of -5
o
C or less. The
calibration gasses should be from a reliable supplier, since the quality of the tank concentration values
ultimately determines the accuracy of the analyzer.
02808 Rev. E Page 15