PRESIDIUM DC709N, User Handbook Manual, Page: 17 / 138

Press and hold the “DISPLAY” button and wait until the
displayed number remains stable (about 2 seconds)
(Fig. 2.6).
Note: The 7-simulant set gemstones are used with the aid
of the reflectivity chart at the back of the unit for calibration
and functional testing of the Reflectivity sensor.
Tips for using your Presidium Duo Tester
If the tester is being used for the first time, or if the tester
has not been used for a week, it is advisable to clean the
probe tip using a piece of paper to attain consistent and ac-
curate reading. Rub the tip gently across the paper surface
before testing.
The probe tip must be placed at a right angle or
perpendicular to the facet of gemstone for an accurate
reading
Tests should be conducted on the table of the gemstone.
In the event of any doubt, kindly test on the girdle of the
gemstones instead.
When mounted stones are not recessed in their setting,
their reflectivity can be measured. Use a black plastic box
(e.g., photographic film container) as an alternative to the
recessed cylinder.
To achieve optimum accuracy for tests involving very small
gemstones (10 points and below), it is important to allow
the gemstone to cool down before subsequent tests.
It is advisable to take multiple readings regarding the test
results indicated.
Fig. 2.6
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