YSI 9300 Photometer - Manual (Page 6)

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In certain methods, the test can be continued to a further stage - for example
in the tests free chlorine and total chlorine. This is accomplished in the
programming of the photometer. In these tests, once the first stage result is
obtained, the ‘Follow-On’ option may be selected to progress the test to the
next program stage or stages and the result will be calculated automatically.
These continuation programs have their own program number for reference
purposes although direct access to these programs may be restricted.
Blank and Sample Tubes
A BLANK TUBE is needed each time the photometer is used. This enables the
instrument to be set automatically and compensates for any inherent color in
the test sample.
The BLANK TUBE is a test tube filled only with the sample being tested. It is
important to use the actual sample to be tested to provide a true comparison
for the test results.
The term 'SAMPLE TUBE' is used to describe the tube containing the sample
and the reagents which have been added in accordance with the appropriate
test instructions. This tube is used to take the photometer reading.
Light Cap
A light cap is provided with the photometer. This cap fits over the test chamber
and prevents excess light from reaching the photodiode.
It is not necessary to use the light cap when using the photometer indoors or
under shaded outdoor light. The light cap should however be used when
working outdoors in strong sunlight. The light cap is also recommended when
carrying out turbidity-based tests such as the cyanuric acid test, under bright
or variable lighting conditions. Test instructions indicate when the light cap
should be used.
Getting the Best Results
Success in obtaining accurate and consistent test results will depend on the
care with which test procedures are carried out. Always follow the test
instructions carefully and observe the stated standing periods and temperature
conditions where applicable.
Wipe test tubes free from condensation before placing in the photometer. Test
tubes should always be kept in a clean condition. Wash and dry carefully after
use. Dirty tubes may be soaked in weak detergent solution if necessary.
Tubes which become stained or scratched in use should be replaced.