Thermo Scientific 49iQ, Instruction Manual

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Calibration
Periodic Zero and Span Checks
4-12 49iQ Instruction Manual Thermo Scientific
In order to achieve data of the highest confidence, it is suggested that
periodic zero air and span checks be performed. These checks can be
performed by:
1. Periodically challenging the instrument with zero air. The output of the
zero air supply should be greater than the flow demand of the
instrument. In addition, an atmospheric dump bypass should be
utilized to ensure that the zero air gas flow is being delivered at
atmospheric pressure. Record the response in percent of scale as A
O
.
Compute the zero drift from the following equation:
= % Drift Zero
A
O
- Z
where:
Z = Recorder response with zero air, % scale
2. Periodically challenging 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. Record the analyzer response in % of scale as
A80. Compute the span error from the following equation.
Z 100
URL
) (O
(%Scale) sponse RecorderRe
out 3
  
where:
A
80
= Recorder response with 80% URL
Z = Recorder response with zero air, % scale
[O
3
]out = Generated span concentration, ppm.
URL = Upper range limit
3. A zero drift in excess of ±4% of fullscale, or a span drift in excess of
±6% of fullscale is an indication of a malfunction either of the zero air
supply, ozone source, recorder, or analyzer. Since the 49iQ 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
Periodic Zero and
Span Checks