Calibration
Periodic Zero and Span Checks
Thermo Fisher Scientific
Model 15
i
Instruction Manual
4-5
recorder response (percent scale) = (([HCl]
OUT
x 100)/URL) + Z
HCl
Where:
URL = nominal upper range limit of the instrument operating range
Z
HCl
= instrument response to zero air, %scale
5.
Record the HCl concentration and the instrument’s response.
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
●
any time the zero or span checks give results outside the limits
described in the “
Periodic Zero and Span Checks
” that follows
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 HCl level of
approximately 80% of the URL. The 80% URL level may be obtained
by dilution of a higher level of HCl using a system similar to that of
Figure 4–1
, or by using a low level cylinder of HCl containing HCl in
air at a concentration of approximately 80% of the URL.
Calibration Frequency
Periodic Zero and
Span Checks
