CHAPTER 3, CALIBRATION
98307600 Rev. C-1 3-15
Use of a Level 1 span calibration (with SPAN COMP: ENABLED and
CALIBRATION: TIMED) adjusts the instrument gain so the output of the instrument
agrees with the concentration expected for span gas. The previously determined
multipoint calibration curve is used to verify that the analyzer output is linear.
Note that a Level 1 span calibration requires external zero and span standards
connected via the (optional) EZS valve assembly.
It is recommended that the CO gas cylinder be checked against the previous
instrument calibration curve immediately after the generation of the calibration
curve (refer to Section 2.0.7 of Calibration Reference 1). It is also recommended
that the concentration of this pollutant source be between 70% and 90% of the
upper range limit of the analyzer and previous calibration curve. Subsequent use
of this pollutant source, with AZS and compensation enabled, adjusts the span of
the instrument to agree with the previous calibration line. Specific guidelines are
contained in Calibration Reference 1 for use of Level 1 span checks
(Section 2.0.9) and certification of gas cylinders to SRM/CRM sources
(Section 2.0.7).
Note
Use of SPAN COMP: ENABLED is not allowed under
U.S. EPA designation at this time.
A Level 2 span check (with SPAN COMP: DISABLED) does not require certification
of the span gas used during AZS, and the result of such a check may not be used
to correct the data, but merely serves to indicate that the analyzer is functioning
properly. If the AZS is used for a Level 2 span check, the SPAN COMP must be set
to DISABLED. A Level 2 AZS cycle should be initiated immediately after
multipoint calibration so that a valid reference point can be determined.
As described in this section, two modes of operation are possible. In the INTERNAL
mode, the internal zero air scrubber is used as the source of zero air. In the
EXTERNAL mode, the user must supply zero air through the Zero inlet of the
optional EZS valve. In the EXTERNAL mode, the Outlet port is connected with a
short piece of tubing to the Inlet port.
In either mode, the user must supply the span gas. In the INTERNAL mode, the
span gas is connected to the Auxiliary port of the instrument. In the EXTERNAL
mode, the span gas is connected to the Span port of the instrument.
These gases (zero, if applicable, and span) must be provided to the analyzer at
atmospheric pressure; for example, through a manifold as shown in Figure 3-1.
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