conductance measuring prinziple
At least two electrodes have to come in contact with the material which is being measured, at the depth of were the moisture content is known. An logarithmicamplifier measures the electrical resistance and a linerisation module calculates the moisture value. The electrical resistance is also influenced through temperature differences, different salt concentrations and the contact to the material. It's necessary to damage the surface for measuring the wished depth. The highest moisture between the electrodes is most effective for the shown moisture result.
The wet core in wood mostly isolated through the dry outside layers, therefore for measuring the wet core you have to chop the wood or to hammer the electrodes to the core.
Caused through different incrediences at different materials we need different calibrations für differen materials.
The core of the wood is typically isloted by the outside layers. Therefore is can not be measured from the outside. The measaurement can be made at fresh cutt places or with penetrating electrodes.
At paper the conductance measurement is possible till approx. 15%.
Properties:
- each measurement takes some seconds for e.g. hammering the electrodes into the wood and also the measurement of high resitance takes time.
- no average measurement! the highest moisture at the electrodes is taken for calculating the moisture content, at inhomogen materail (moist core and dry outside layers) an average moisture cannot be measured.
- the result is depending on the temperature!
- It's not possible to measure coated or paint materials without damaging it!
- different salt concetrations are influence the measurement!
- 2 measuring points are enough
