YSI 9500 Photometer - Manual (Page 11)

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 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 or under bright 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.
Taking Test Readings
1 Press key. The instrument will beep and display the ‘Choose a Test’
menu box, with the last test program used highlighted as the active line.
The cursor will flash on ‘OK’ in the options menu at the bottom of the
screen.
Press [OK] to accept this program and follow the on-screen instructions for
the chosen test.
2 To choose a different test program, either use the and keys to scroll
through the menu options, or use the numeric keys to enter the Phot
number of the desired test. The four most recently used tests are listed at
the top of the ‘Choose a Test’ screen for convenience.
Press [OK] to accept the selected program.
3 If the sample number option is pre-selected, then the following display will
appear, for example :-
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