A self-monitoring strategy for TRIME Time Domain Reflectometry moisture sensors

Time Domain Reflectometry (TDR) is widely used to determine the water content of porous media. However, the raw TDR signal is susceptible to electromagnetic interference (EMI) that can lead to faulty measurements. I developed a self-monitoring strategy for real-time data evaluation that is applied in TRIME TDR sensors, in which the strategy can also be adapted to other conventional TDR sensors. The self-monitoring strategy combines moving variance and Pearson correlation methods to improve data integrity. Particularly, the strategy helps to avoid undetectable false measurements and eases the complexity of filter implementation within the sensor. In evaluations, I examined the influence of the EMI, between 100 kHz to 6 GHz, on TRIME TDR sensors under conducted and radiated disturbances induced by radio-frequency fields according to the IEC 61000-4-3 and the IEC 61000-4-6 standards. Finally, the measurement fluctuation is significantly improved resulting in a data tolerance of lower than 4 % under induced radio-frequency disturbances.