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Service manual
4.3.7. Photometry tests
This screen contains a set of tests to check the functioning of the optical system. The tests are classified under
different tabs. First of all, the base line and darkness count tests must be made in order to be able to carry out the
remaining tests. To perform these tests, the analyzer must be initialised.
The optical system has a photodiode that generates an electrical current proportionate to the light intensity on it.
time. An AD converter converts the accumulated load into a digital value called count number, between 0 and
1048576. During normal functioning, the analyzer automatically adjusts the integration time for each filter when
the analysis begins and after initialisation. When the first photometry test is performed, the integration times are
also automatically adjusted. These times are adjusted in such a way that the count number of the base line for
each wavelength is as near as possible to 950000. In this way, the dynamic range of the detection system is
adapted to the light intensity present at each wavelength. The filter wheel has 10 positions. Position 0 must
always contain a covered filter so that the analyzer can perform the darkness adjustment. Positions 1 to 9 can be
used for optical filters.
4.3.7.1. Base line and integration times
When this test is run for the first time, the analyzer fills the first 3 rotor wells with distilled water. The analyzer
automatically adjusts the integration times and makes a base line with each of the available filters in each of the
3 wells. The program shows the current integration times for each of the filters and the average for the 3 wells of the
count numbers obtained with each filter. The screen shows the corresponding alarms in the case of anomaly. It is
also possible to access a screen where it is possible to manually vary the integration times to check their effect
on the count numbers. And another screen where it is possible to assign calculated integration times as reference
integration times for each filter. This screen is recommended when a filter or the lamp is physically changed. After
performing the test, the analyzer continues to take optical readings using the automatically adjusted integration
times.
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