Self-Oscillating Measurement System for In Situ-Monitoring Moisture in Buildings

A compact and inexpensive microwave system for in situ monitoring the moisture content in concrete structures is presented. It consists of an active microwave sensor and a frequency meter. Both components and their integration are briefly described. To cover the vast moisture range of interest, the system is calibrated against the wet basis moisture content and the ambient (equilibrium) relative humidity. The system's suitability for the given task is evaluated under realistic conditions.