Thermo Scientific 49i Instruction Manual page 148

Calibration
Periodic Zero and Span Checks
4-12 Model 49i Instruction Manual
2. Record the analyzer response in percent of scale as A
drift from the following equation:
ZeroDrift %
where:
Z = Recorder response obtained at the last calibration for zero air, % scale
3. Periodically challenge the instrument with an ozone level of
approximately 80% URL from a previously calibrated stable ozone
generator.
The output flow from this generator should be greater than the flow
demand of the instrument. In addition, an atmospheric dump bypass
should be used to ensure the span gas flow is being delivered at
atmospheric pressure.
4. Record the analyzer response in % of scale as A80. Compute the span
error from the following equation:
Reported CO Concentrat
Actual
where:
Z = Recorder response obtained at the last calibration for zero air, % scale
[O ] = Generated span concentration, ppm
3
A zero drift in excess of ±4% of full scale, or a span drift in excess of
±6% of full scale is an indication of a malfunction either of the zero air
supply, ozone source, recorder, or analyzer. Since the Model 49i is a ratio
instrument and thus does not have an electronic span or zero drift, it is
not recommended that any zero adjustment or span adjustment be
performed as the result of a zero or span check. If values are obtained
outside of the limits of ±4% for zero and ±6% for span drift, the
multipoint calibration described previously is indicated to isolate the
problem.
For detailed guidance in setting up a quality assurance program, refer to
the code of Federal Regulations, and the EPA Handbook on Quality
Assurance.
A Z
o
ion Actual CO
CO Concentrat ion
. Compute the zero
o
(6)
Concentrat ion
100
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