Development of a technique for the measurement of moisture levels in building materials

Abstract

A method is described for measuring the moisture content of building materials on site. It is based on a capacitance measuring technique in which the moist sample acts as a capacitor connected in parallel with a resonant LC circuit, detuning it. The degree of detuning is a measure of the capacitance, which in turn is a measure of the moisture content of the sample. The oscillator frequency was 84.5 MHz, and extensive precautions were taken to eliminate stray capacitance effects and temperature instabilities. The final device has shown itself to be suitable for on site measurements, with minimal interference with the wall, and with a small and correctable sensitivity to dissolved salts.