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All gas must be supplied to the instrument at atmospheric pressure. It will
be necessary to employ an atmospheric bypass plumbing arrangement to
accomplish this.
If a filter is used, all gas must enter the instrument through the filter.
For detailed information about the menu parameters and the icons used in
these procedures, see the "Operation" chapter.
Use the following procedure to check the zero/span.
1. If the instrument is equipped with the optional zero/span and sample
valves, connect the zero and span gas to the rear panel bulkheads
labeled ZERO and SPAN, otherwise connect a source of vented zero air
to the SAMPLE bulkhead.
Note Do not use nitrogen for zero air.
is used to activate the zero and span valves. The lower left-hand
corner of the Run screen indicates which mode is active: ZERO,
SPAN, or SAMPLE.
2. To ensure that the zero air is being measured at atmospheric pressure
check that the flow reported by the analyzer is approximately 0.5 LPM.
Actual zero air flow should be 0.8 LPM or more, with the excess
flowing out the atmospheric bypass.
a. From the Run screen, press
b. From the Main Menu, select Diagnostics >
the Sample Flow screen.
c. Make sure that the reported sample flow is less than the actual zero
air flow.
3. Press
to monitor the zero air reading and wait for the reading to
stabilize.
4. Record the measured SO
adjustment. If the zero has changed by more than ± 1.5 ppb, it is
recommended that a new calibration be performed.
5. Connect a source of vented span gas to the SAMPLE bulkhead. The
span gas should be approximately 80% of the full-scale range.
▲
to display the Main Menu.
value as the zero drift since the last
2
Model 43i Trace Level-Enhanced Instruction Manual
Calibration
Zero/Span Check
> Flow to display
4-11
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Troubleshooting
