Application of a LTCC sensor for measuring moisture content of building materials

In this paper, the application of a passive sensor for measuring the moisture content of building materials is described. The sensor was fabricated in Low Temperature Co-fired Ceramic (LTCC) technology, and consists of an inductor and an interdigitated capacitor. It is embedded in the test sample of a building material which has been set in pool water, so that changes in the moisture content of the specimen can be measured wirelessly tracking changes in the sensor resonant frequency. A clay brick and an autoclaved aerated concrete block were used for analysis and testing sensor’s performances. Dielectric constant of water is much higher compared to the permittivity of test samples, and the increased moisture content in the samples increases the capacitance of the LC resonant sensor and consequently decreases the sensor resonant frequency.