Calibration Curve; Periodic Zero And Span Checks - Thermo Scientific 49i Instruction Manual

Calibration Curve

Periodic Zero and
Span Checks
Thermo Fisher Scientific
2. For each ozone concentration standard, record the ozone concentration
as determined by the calibration photometer and record the
corresponding Model 49i analyzer response.
If a Model 49i Primary Standard is being used as the calibration
photometer, use the ozone concentration as determined by the
photometer and not the value of the ozone level thumbwheel.
Use the following procedure to plot the calibration curve.
1. Plot the Model 49i Analyzer responses versus the corresponding ozone
concentrations.
2. Connect the experimental points by using a straight line, preferably
determined by linear regression techniques.
Points that lie more than ±4% from this line are an indication of an
error in determining the calibration curve. The error may be due to a
malfunction of the calibration photometer, or a malfunction of the
analyzer being calibrated. The most likely malfunctions in both the
analyzer and calibration photometer which can give non-linear results
are leaks, a malfunctioning ozone scrubber, a dirty solenoid, or dirt in
the optical system. The calibration curve is used to reduce subsequent
ambient data.
Note To generate data of the highest confidence, it is recommended that a
multipoint calibration be performed every three months, any time major
disassembly of components is performed, or any time the zero or span
checks give results outside the limits described in "Periodic Zero and Span
Checks" that follow.
In order to achieve data of the highest confidence, it is suggest that periodic
zero and air span checks be performed. These checks can be performed by:
1. Periodically challenge the instrument with zero air.
The output flow of the zero air supply should be greater than the flow
demand of the instrument. In addition, an atmospheric dump bypass
should be used to ensure that the zero air gas flow is being delivered at
atmospheric pressure.
Calibration

Periodic Zero and Span Checks

Model 49i Instruction Manual 4-11