Patent ID: 6904789

Claim:
A sensor for measuring water content of bulk materials, the sensor being powered by a direct current excitation, the sensor comprising: an oscillator to provide a square wave voltage signal; a transmission line having an input and an output, the transmission line input being coupled to receive the square wave voltage signal, the transmission line output being coupled to a phase detector; the phase detector detecting a phase difference between the square wave voltage signal provided by the oscillator and the signal provided to the transmission line, the phase detector providing an output signal indicative of the phase difference caused by changes in moisture content of a medium surrounding the transmission line wherein the phase detector comprises: a semiconductor circuit having first and second inputs and an output, the output of the semiconductor circuit being indicative of a logical exclusive OR function of signals applied to the first and second inputs of the semiconductor circuit, the first input of the semiconductor circuit being coupled to the oscillator to receive the square wave voltage signal and the second input of the semiconductor circuit being coupled to the transmission line; a low pass filter providing a direct current output proportional to moisture content.