capacitive measuring prinziple

This is the most cost effective measuring principle to measure the moisture without damaging the material. 

The meter are  working in accordance with the principle of an opened plate capacitor. The capacity of the capacitor depends on the material-(dielectric)-constant (DC) of the material in between the plates (3). Compared with air, for example (DC = 1) water has got a very high dielectric-constant (DC ~ 80). The water content of a wet material can therefore be determined by determining the dielectric constant of this material (2).

Properties:

• The measurements are influenced through differences in the material densities and material mixture. 
• very quick measurement, after pressing on the sensor, the moisture value can be read immediately
• an average moisture alue will be measured. The measurin depth depends
• average measurement ! the measuring depth depends on the mositure and on the material to be measured. At wood it is approx. 3 cm, at concrete approx 6 cm. The influence to the measurement result gets less with higher depth. 
  At dry outside layers, a wet core sometimes can not be measured!
• in the temperature range 5 - 40°C there is nearly no temperature dependency.
• coated and painted materials can be measured without damaging!
• for accurate ,measurements a smooth surface is necessary
• the result depends on the density of the materials. Frames in walls can be detected