Speed sensor for a rotating member or machine

摘要

A speed sensor for use in measuring the speed of rotation of a rotationally salient rotating member. The speed sensor comprises an electrode and a sensor circuit. The sensor circuit comprises a constant voltage source for supplying a voltage to the electrode to generate an electric field in a dielectric medium. A current detector detects current flow between the constant voltage source and the electrode due to perturbation of the electric field by passage of at least one salient feature of the rotating member through the electric field as the rotating member rotates. The current detector outputs a first signal modulated at a frequency corresponding to the frequency of perturbation of the electric field. The first signal is amplified to produce an amplified signal modulated at a frequency corresponding to the frequency of perturbation of the electric field.

主权项

1. A speed sensor for use in measuring the speed of rotation of a rotationally salient rotating member, the speed sensor comprising an electrode and a sensor circuit;
the sensor circuit comprising: a constant voltage source configured to supply a constant voltage without polarity reversal between the electrode and the rotating member to establish a potential difference between the electrode and the rotating member and thereby establish an electric field which extends in a dielectric medium from the electrode to the rotating member; a current detector for detecting current flow between the constant voltage source and the electrode due to perturbation of the electric field by passage of at least one salient feature of the rotating member through the electric field as the rotating member rotates, the current detector outputting a first signal modulated at a frequency corresponding to the frequency of perturbation of the electric field; and an amplifier circuit comprising a signal amplifier for amplifying the first signal and outputting a second signal modulated at a frequency corresponding to the frequency of perturbation of the electric field such that the speed of rotation is determined based upon the frequency of the modulation of the second signal; wherein the sensor circuit further comprises a capacitor connected between the electrode and the signal amplifier, the capacitor acting to isolate the signal amplifier from the constant voltage applied to the electrode.