Time Domain Reflectometry flat sensor for non-invasive monitoring of moisture changes in building materials

•Noninvasive sensor for moisture detection.•Utilizing the Time Domain Reflectometry potential.•Cheap and prospective for practical applications.•Applicable for non-invasive moisture changes monitoring in rigid porous materials. The article presents the monitoring potential of a simplified surface Time Domain Reflectometry (TDR) sensor design. Its basic element is a polyvinyl chloride (PVC) plate with two rods placed along the plate edges. The paper describes typical, invasive TDR sensors and the attempts to build a non-invasive TDR sensor for the dielectric moisture determination. The newly developed flat TDR sensor presented in this article has a simple design, which makes it cheap, easy to carry and prospective for practical applications. Within the conducted examinations, the developed sensor specimens were calibrated and tested in an exemplary moisture transport experiment. The analysis of moisture changes in the sample of the examined material confirmed the usefulness of the developed TDR sensor and its applicability for the non-invasive moisture changes monitoring in hard porous materials.