Contact-Less Speed Probe Based on Eddy Currents

In this work, we present a technique for the speed measurement of a metallic body with flat surface and without marks, using a contact-less probe. Basically, the measurement system is made with a permanent magnet for the magnetic field generation and a Hall plate as pick-up sensor. The contact-less probe geometry, the electronic circuit and the devices used for the output signal treatment, including a suitable signal processing applied to increase the signal noise ratio are described. In addition, a theoretical analysis of the probe sensitivity is proposed. In order to show the practical performance of the speed measurement proposed, a series of experimental tests is presented.