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Teledyne API Model 200A NO
X
Analyzer Instruction Manual, 02246, Rev. G, DCN 5247
7.8.2.2 Selection of NO Span Gas Standards
The NIST-SRM's provide references against which all calibration gas mixtures must be
compared (Section 2.0.7, Q.A. Handbook). The procedure requires the comparison of the
concentration of a commercial, working calibration standard to an NIST-SRM. This is described
in Subsection 7.1 of Section 2.0.7, Q.A. Handbook. Subsections 7.1.4 and 7.1.5 describe the
verification and reanalysis of cylinder gases.
Care must be taken to assure that no oxygen is allowed in the NO tank, regulator, or sample
lines. If oxygen is present, it reacts with NO to produce NO
2
which can lead to significant errors
in NO concentration measurement.
It is good practice to request a NO
x
analysis from the supplier of the NO calibration gas.
Generally the maximum NO
2
impurity that should be allowed is 1% of the NO concentration.
The NO
2
impurity in the NO standard can be measured by the M200A. A procedure is given in
the TAD for NO
2
measurement.
7.8.2.3 Use of NO
2
Permeation Tubes As Standards
The steps required to compare the concentration of a commercial working calibration standard to
an NIST-SRM are described in Subsection 7.3.3 of Section 2.0.7, Q.A. Handbook. See
Subsection 7.3.6 for the re-analysis of permeation tubes.
7.8.3 Data Recording Device
Either a strip chart recorder, data acquisition system or digital data acquisition system should be
used to record the data from the M200A’s RS-232 port or analog outputs. If analog readings are
being used, the response of that system should be checked against a NIST referenced voltage
source or meter. Data recording device should be capable of bi-polar operation so that negative
readings can be recorded.
7-15
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