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Model 9110T NOx Analyzer EPA Protocol Calibration
Teledyne Analytical Instruments 234
Zero/Span checks through remote contact closure can be initiated through remote contact closures
on the rear panel. See Section 9.4.3.3 of this manual.
Zero/span checks can also be controlled through the RS-232 port. See Section 8 of this manual for
more details on setting up and using the analyzer’s RS-232 port.
10.8.4. PRECISION CHECK
A periodic check is used to assess the data for precision. A one-point precision check must be carried out
at least once every 2 weeks on each analyzer at an NO
2
concentration between 0.08 and 0.10 ppm.
The analyzer must be operated in its normal sampling mode, and the precision test gas must pass
through all filters, scrubbers, conditioners, and other components used during normal ambient
sampling.
The standards from which precision check test concentrations are obtained must be traceable to
NIST-SRM SRM. Those standards used for calibration or auditing may be used.
10.8.4.1. Precision Check Procedure
Connect the analyzer to a precision gas that has an NO
2
concentration between 0.08 and 0.10 ppm. An
NO
2
precision gas may be generated by either GPT or a NO
2
permeation tube. If a precision check is
made in conjunction with a zero/span check, it must be made prior to any zero or span adjustments.
Allow the analyzer to sample the precision gas until a stable trace is obtained.
Record this value.
NO and NO
X
precision checks should also be made if those data are being reported. Information
from the check procedure is used to assess the precision of the monitoring data; see in Section 12
of the Q.A. Handbook
6
for procedures for calculating and reporting precision.
10.9. CERTIFICATION OF WORKING STANDARDS
The NO content of the NO working standard must be periodically assayed against NIST-traceable NO or
NO
2
standards. Any NO
2
impurity in the cylinder must also be assayed. Certification of the NO working
standard should be made on a quarterly basis or more frequently, as required. Procedures are outlined
below for certification against NO traceable standard which is the simplest and most straightforward
procedure.
To assure data of desired quality, two considerations are essential:
The measurement process must be in statistical control at the time of the measurement and;
Any systematic errors, when combined with the random variation in the measurement process, must
result in a suitably small uncertainty.
Evidence of good quality data includes documentation of the quality control checks and the independent
audits of the measurement process by recording data on specific forms or on a quality control chart and
by using materials, instruments, and measurement procedures that can be traced to appropriate standards
of reference.