Noninvasive Time Domain Reflectometry Moisture Measurement Probe

Abstract Time domain reflectometry (TDR) has been shown to be a widely applicable method for determination of moisture content in soils and other geological and engineering materials. All TDR probes used to date have required penetration of the sample under study, which severely limits the utility of the method. We demonstrated that, by simply placing the probe wires against the surface of a sample and recalibrating the dielectric vs. moisture content response, the TDR method may be used to obtain moisture content without sample penetration. This expands the range of applicability of the TDR technique to such critical areas as hard rock drill cores and pavement measurements, as well as endurated soils. An example of such a noninvasive probe is shown to have the accuracy of previous probe designs (i.e., ± 2% m 3 m −3 moisture content), without requiring penetration of the sample, with additional advantages including the ability to miniaturize the probe.