2. Measuring / calibrating over 50% (0.5 aw) HC2(A)-AW the measurement is not accurate. Why is that?

When measuring higher humidity or water activity values with long measurement times (be that a calibration or a slowly equalising sample), it's important to make sure that the O ring on the bottom is clean and not damaged so the seal between the inside sample chamber and outside environment is good.

In some cases the use of a mechanical clamp to improve this seal can be used. The AW-KHS clamping device can help here to improve the measurement. It will press the measurement head to the sample holder to ensure good quality seal and therefore prevent outside air interference with the micro-climate of the measuring chamber.