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Additional Concentration
Standards
Thermo Fisher Scientific
5% of scale. This is to allow observation of zero drift and/or zero noise.
Record the stable zero air response as Z.
Span Adjust
Use the following procedure to adjust the span.
1. Adjust the zero airflow and the CO flow from the standard CO
cylinder to provide a diluted CO concentration of approximately 80%
of the full-scale range that the unit will be operating under. For
example, if the analyzer will be run on the 50 ppm range, the span gas
concentration should be about 40 ppm.
2. Allow the analyzer to sample this CO concentration standard until a
stable response is obtained.
3. Press
The display shows the current CO concentration reading. The next line
of the display shows the actual CO concentration of the gas as
calculated from the air and span flows.
4. Enter the CO calibration gas concentration using the pushbuttons to
adjust the display value to match the actual concentration being
delivered by the gas titration system, and then press
instrument's span-factor and force the CO reading to match the true
CO concentration of the span gas.
If a strip-chart recorder is being used to record the analog output, the
recorder response should now be:
recorder response (percent scale) = (([CO]OUT x 100)/URL) + Z
Where:
5. Record the CO concentration and the analyzer's response.
Generate several additional concentrations (at least five others are
suggested) by decreasing F
total flow exceeds the analyzer's total flow demand. For each concentration
and choose Calibration > Cal Coefficient.
URL = nominal upper range limit of the analyzer's operating range
Z
= analyzer's response to zero air, %scale
CO
or increasing F
CO
. In each case, be sure the
D
Model 48i Trace Level-Enhanced Instruction Manual
Calibration
to adjust the
CO
4-11
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Troubleshooting
