12 Maintenance
Cleaning the Optical Bench
There is a Balston air filter in-line on the flow path leading to the IRGA optical
bench. It is very important that incoming air be filtered. This is because any dirt in
the optical cell will cause an immediate zero shift.
The optical bench can be removed and cleaned if necessary. If the optical path
becomes dirty it may become difficult to span the analyzer. Excessive zero drift
may also be observed if the optical path becomes dirty. If significant dirt
accumulates in the optical bench, linearity errors that exceed the stated
specifications can also result.
Follow these steps to clean the optical bench:
NOTE: Make sure that you are properly grounded to avoid any electro-static
discharge events that can damage the internal components.
1. Power the instrument off and remove the battery or other external power
source.
2. Open the Analyzer Control Unit case and remove the access panel by
loosening the 4 thumbscrews.
3. Mark one of the Balston air filters with a marker or piece of tape to make sure
that you are able to return them to their original locations when re-
assembling. This is important, as one of the filters is in-line with the bellows
air circuit to the Survey Chamber, and is bi-directional, meaning dirt can be
introduced into the filter in both directions. If this filter is inserted into the
optical bench air path during re-assembly, dirt can be inadvertently blown
into the optical bench.
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