A SENSOR

摘要

A sensor for sensing at least one parameter of a medium including sensing electrodes (6, 8) arranged to form a capacitor, each electrode having an insulating film (9) such that when the sensor is located in the medium each electrode is electrically insulated from the medium. The sensor also includes means for applying a measurement signal to the capacitor to obtain at an output a sensed signal, and means for processing the sensed signal to derive the at least one parameter of the medium. A capacitance value which is attributable to the insulating film is used to process the sensed signal. In a typical application the sensor is used for measuring moisture content and/or salinity of a soil medium.