Calibration
Periodic Zero and Span Checks
4-6
Model 48
i
Instruction Manual
Thermo Fisher Scientific
In order to generate data of the highest confidence, it is recommended that
a multipoint calibration be performed:
●
every three months
●
any time any major disassembly of components is performed
In order to achieve data of the highest confidence, it is suggested that
periodic zero and air 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 is the recorder response obtained at the last calibration for zero air, % scale
2.
Periodically challenging the instrument with a CO level of
approximately 80% of the URL. The 80% URL level may be obtained
by dilution of a higher level of CO using a system similar to that of
Figure 4–1
, or by using a low level cylinder of CO containing CO in
air at a concentration of approximately 80% of the URL. In either case
the cylinder of CO should be checked against an SRM or CRM. It
should also be true for a cylinder of low level CO.
The
Quality Assurance Handbook
1
should be referred to for the cylinder
checking procedure.
Compute the span error from the following equation:
100
ion
Concentrat
CO
Actual
ion
Concentrat
CO
Actual
ion
Concentrat
CO
Reported
Calibration Frequency
Periodic Zero and
Span Checks
