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12. Checking the calibration
Requirement: Calibration ampoules (humidity standards art.no.10005). Use for the
calibration one of the screw-top jars with a filling quantity of 186 ml. The device, the
water activity measuring chamber and the humidity standards must have a tempera-
ture between 20.0 °C and 26.0 °C. It is recommended to store the device, the water
activity measuring chamber and the calibration ampoules for 24 hours in a room with
low temperature fluctuation.
Perform the calibrationin in the approximate application range.
Example: For measurements between 0.2 and 0.5 aw use the humidity standards 35 %
and 50 % rh.
12.1 Preparing the water activity measuring chamber
1. Clean the screw-top jar thoroughly (see "11.3 Cleaning the device").
2. Place the textile pad into the screw-top jar (figure 65)
and carefully pour the humidity standard onto the pad.
3. Hold the ampoule by the neck and release the entire
liquid into the lower part of the ampoule by light
tapping.
4. Now carefully break the head of the ampoule on the
marked spot.
5. Pour the solution completely onto the textile pad in the glass. Tighten the aw-
Value measuring chamber well.
» Recommendation: Keep the screw-top jar on the table while screwing.
» If necessary, only lift the water activity measuring chamber straight up, do not tilt
or turn it over.
6. In case it has been lifted, carefully place the water activity measuring chamber
onto an even table.
» Make sure to lift the water activity measuring chamber straight up and not to tilt
or turn it over. Otherwise the sensor may be damaged.
65
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