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EPA Protocol Calibration
Model 400E Ozone Analyzer
Instruction Manual
192
P/N 04316 Rev: B
8.3.
Multipoint Calibration
8.3.1.
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 8.1.4). The user should be sure that all flow-meters 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 M400E should be operated for several hours or preferably
overnight before calibration to allow it to stabilize. A brand new M400E (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.
8.3.2.
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 procedures for performing the Zero Point and High Span Point are identical to
those described in Sections 7.2 and 7.3.
After the Zero and High Span points have been set, determine five approximately
evenly spaced calibration points between the Zero and High Span Point.