Many damages in buildings, particularly in old buildings, are direct or indirect consequences of moisture.For a diagnosis of moisture in building materials it is necessary to measure remotely, non-destructively, and with high selectivity. The method should be able to locate areas with excessive moisture. In the past around infrared reflective thermography has mostly been used for moisture detection. With such measurements it is possible to measure non-destructively large surface areas. But this measuring method is questionable, because the influences of secondary phenomena like the emission coefficient, theleaking radiation, and the geometric and surface conditions allow only a qualitative measurement of the surface moisture.We developed the amplitude sensitive modulation thermography. This method utilizes the absorptionproperties of water in the wavelength of 1.94μm and a reference wavelength band at 1.0μm. The result of this measurements is an amplitude image produced at 1.0μm and 1.94μm.For better comparability and reproducibility we generate a surface moisture image from the reference- and the measuring effect wavelength band. With a preliminary calibration in laboratory the qualitative and quantitative detection of surface moisture isachieved.The method eliminates the influence of leaking radiation, geometric, and surface condition effect. The results from laboratory tests were confirmed at an historical building under practical conditions.
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