PRESIDIUM Gem Tester II Mode D'emploi page 122

3. Adjust the indication needle so that
it moves to the center of the red
"GLASS" strip by fully depressing
the probe tip against the "GLASS"
Disc while simultaneously adjusting
potentiometer C2 with a screw
driver.
4. Repeat steps 2. & 3. till indicator needle falls in the center on both "GLASS" & "CAL" strips.
Note: As the probe tip is sensitive to changes in surrounding temperature, kindly ensure that recalibration
is not conducted in environments of direct wind and should be performed in a stable environment. It is
also normal to perform re-calibration 2-3 times to achieve the tester's optimal calibration.
Fig. 3