Trotec T500 Bedienungsanleitung Seite 59

Procedural instructions for the measurement
of moisture in building materials
• Before making measurements on building materials,
the correct sensor mode (mode 100) must be selected.
• The temperature of the building material should lie around
20 °C when measuring its moisture content.
• Note the disruptive influence of electrically conductive
salts in building materials:
Building-related moisture problems often occur in combination
with water-soluble salts. Salts improve the electrical
conductivity of a building material considerably. The result of
the resistance measurement is falsified such that a higher
measured value is displayed. Salts ionise when they dissolve,
i.e. the differently charged components (ions) of the dissolved
salt crystal separate.
If the moisture content of a building material containing water
with dissolved salts is measured, a voltage is applied across
the salt solution via the electrodes.
The positive salt ions drift to the negative electrode and the
negative ions drift to the positive electrode. The ions
neutralise their charge at the electrodes, which corresponds to
the flow of electrical current. This additional current is added
to the measuring current, whereby the measuring current and
Operating manual – English
B - 26