INDUCTIVE SENSOR

摘要

A sensor for sensing an external parameter such as temperature or the presence of an object, for example a human finger, comprises: (i) an excitation coil (68,70); (ii) a signal generator (41, 61, 62, 63) operable to generate an excitation signal and arranged to apply the generated excitation signal to the excitation coil; (iii) a sensor coil (74) that can be eiectromagnetically coupled to the excitation coil via an intermediate device or target (74), normally in the form of a passive resonant circuit, such that, in response to the excitation signal being applied to the excitation coil by the signal generator, an electric signal is generated in the sensor coil; and (iv) a signal processor that processes the periodic electric signal generated in the sensor coil to determine a value representative of the parameter being sensed. The intermediate device is sensitive to the parameter to be sensed, for example by including PTC or NTC resistors, or capacitors that are affected by the proximity of an object, so that the periodic electric signal generated in the sensor coil is affected by the parameter.