Moisture measurements in building materials by amplitude-sensitive modulation thermography

The cause of much damages in buildings, particularly in old buildings, is a direct or indirect consequence of moisture. For diagnosis of moisture in building materials it is necessary to perform remote measurements non-destructively with high selectivity. The method should be able to locate large areas with excessive moisture. For this presentation of the problem we developed the amplitude sensitive modulation thermography. This method utilizes the absorption behaviour of water in the wavelength of 1 .94 zm and a reference wavelength band at 1 .0 rim. To detect only this two wavelength bands without the influence ofleaking radiation, a modulated illumination is used. For a better comparability and an elimination of measuring effects we generate from the reference- and the measuring effect wavelength band a surface moisture image. With a preliminary calibration in laboratory the quantitative detection of surface moisture is achieved. The results of this investigation eliminate the influence of leaking radiation, geometric and surface conditions effects by reducing emission behaviour of the surface. At the moment the measurements present a trend to measure the moisture in different materials without a material characteristic dependence.