System Setup and Operation
CIRAS-2 Operator's Manual Version 2.04
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Manual Without Warnings: Only recommended if the user is very experienced with gas exchange and
finds the warnings inconvenient. It is also useful where the Zero is under PC control.
Changes in Zero Readings
Whenever CIRAS-2 has been running for longer than 30 minutes, a set of analyzer A/D readings are
stored representing the Reference and Analysis CO
2
and H
2
O values measured after an Automatic Zero
has been completed. Following a Zero, CIRAS-2 checks the new Zero against the stored values in 2
ways:
1. If the current and previous values differ by more that +/- 100, an Error Code 79 is generated („New
Zero Significantly different from previous [79]‟).
2. If more than 4 sets of Stored Zeros are present, CIRAS-2 checks the slope of the data. If the
slope falls out of an acceptable range, an Error Code 78 is generated („Zero Showing Progressive
Change [78]‟).
These messages could simply be the result of a Zero performed when the chemicals are not fresh, and
then the next Zero performed with fresh chemicals. It may also be an indication that a column has not
been replaced properly. Although this may cause the user concern, if the A/D values in Stored Zeros (see
Stored Zeros on page 134) do not differ by much more than 100, there probably is not much of a problem.
If the A/D values differ by more than 100, then it could be a symptom of a greater problem. Ensuring that
the chemicals are replaced regularly, the absorber columns are inserted correctly, and the Zero is
performed under stable conditions will help to avoid this error message.
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