This letter describes a magnetic sensor using a parametric oscillation of a RLC parallel circuit. It is shown that the sensing output voltage of the proposed sensor is proportional to the input and constant against the frequency.

If one of the R, L, or C Parameter of an RLC parallel circuit is changed periodically, under certain conditions, an oscillation called Parametric oscillation occurs. If one of remaining circuit elements is made to change due to an external cause (e.g. an external electric or magnetic field), then the parametric oscillation will experience some modulation. This modulation process and the subsequent demodulation can be exploited to create several types of sensors. In this letter, we describe the features of a new parametric magnetic speed sensor and its application in Induction motor robust control.