Patent ID: 7514919

Claim:
A sensor for sensing a parameter, the sensor comprising: (i) an excitation winding comprising a plurality of coils having different spatial functions; (ii) a signal generator operable to generate excitation signals and arranged to apply the generated excitation signals to the excitation coils; (iii) a sense coil that can be electromagnetically coupled to the excitation winding such that, in response to an excitation signal being applied to the excitation winding by the signal generator, there is generated in the sense coil a periodic electric signal having a phase that is indicative of the value of the parameter to be measured by the sensor; and (iv) a signal processor operable to process the periodic electric signal generated in the sense coil to determine a value representative of the parameter being measured; wherein the signal processor is operable to generate a second signal at a frequency that differs from that of the excitation signal only by a small amount, and to mix the second signal with the signal received from the sense coil to generate a third signal having a frequency component equal to the difference between the frequency of the excitation signal and that of the second signal, and to determine the said value from the phase of the third signal.