Patent ID: 7944220

Claim:
A moisture content sensor, the sensor comprising: a signal source arranged to provide an a.c. signal; a probe arranged to inject the signal into a medium in which the moisture content is to be measured; a complex impedance comprising a PI circuit arrangement provided by a plurality of components including an inductance connected between the first ends of two capacitances provided in parallel with the second ends of the capacitances connected to ground, the Pi-circuit located between the probe and the signal source; and a sensing impedance placed in series between the complex impedance and the signal source, wherein the sensing impedance and the complex impedance together with the impedance provided by the medium into which the probe is inserted during use form a potential divider; and sensing electronics arranged to monitor the signal at the junction of the sensing and complex impedances and to generate a measurement of the signal amplitude and/or phase therefrom which is indicative of the moisture content of the medium.