Non-contact strip speed measurement using electrostatic sensors

Accurate strip speed measurement is desirable in certain manufacturing industries. This paper presents the recent development in the non-contact measurement of strip speed using electrostatic sensors in conjunction with correlation signal processing techniques. A pair of narrow strip electrodes is used to derive signals from a moving solid surface. The speed of the solid surface is then determined from the known spacing between the electrodes and the time delay between the two signals. Experimental tests were conducted on a motorized cable speed test rig under a range of conditions. An optical tachometer was used as a reference instrument to assess the accuracy of the new strip speed measurement system. Basic sensor design considerations and the advantages and limitations of the method are addressed. Results demonstrate that the technique is capable of measuring strip speed with a relative error no greater than +/-1.5% and a repeatability of better than 2%.