In-situ moisture detection system with a vector network analyser

An in-situ measuring system for determining the moisture content in concrete buildings and masonry is presented. The system consists of a small and robust resonant microwave sensor and a compact low-cost network analyser. The sensitivity and frequency range requirements for the analyser are derived from the sensor design. A suitable realization of the analyser is discussed in detail. It is shown that a vectorial calibration routine diminishes measurement uncertainties caused by the used low-cost devices. Consequently, the moisture content can be determined within 0.6% instead of 3.0%. A test of the entire in-situ measurement system under realistic conditions is presented and discussed.