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T400 Ozone Analyzer Operator’s Manual EPA Protocol Calibration
211
10.3. MULTIPOINT CALIBRATION
10.3.1. GENERAL INFORMATION
The procedures for multipoint calibration of an O
3
analyzer by UV photometry or a
transfer standard have been specified in the Code of Federal Regulations
1
. To facilitate
these procedures, operational and calculation data forms have been developed. These
forms will aid in conducting calibrations and quality assurance checks. A detailed
description of the calibration theory and procedures for UV photometry and transfer
standards is in the Code of Federal Regulations
1
and TAD.
2, 3
In general, ambient monitors are always calibrated in situ without disturbing their
normal sampling setup, except for transferring the sample inlet from the ambient
sampling point to the calibration system.
Calibration should be performed with a primary UV photometer or by a transfer
standard (see Section 10.1.4). The user should be sure that all flow
m
eters are calibrated
under the conditions of use against a reliable standard such as a soap bubble meter or
wet test meter. All volumetric flow rates should be corrected to 25°C and 760 mm Hg.
A discussion of the calibration of flow meters is in Appendix 12 of Ref. 11.
A newly installed T400 should be operated for several hours or preferably overnight
before calibration to allow it to stabilize. A brand new T400 (fresh from the factory)
may require several days of operation to fully stabilize. Allow the photometer or
transfer standard to warm up and stabilize before use, particularly if stored or
transported in cold weather.
10.3.2. MULTIPOINT CALIBRATION PROCEDURE
Multipoint Calibration consist of performing a calibration of the instrument’s Zero Point
and High Span Point, then checking its accuracy at various intermediate points between
these two.
The procedure for performing the Zero Point and High Span Point are identical to those
described in Section 9.2.3.
After the Zero and Hig
h
Span points have been set, determine five approximately evenly
spaced calibration points between the Zero and High Span Point.
For each midpoint:
06870C DCN6332