DEVICE FOR DETECTING EXISTENCE OF MOVING ROLLED PRODUCT

摘要

The presence of a magnetic rolled metal product is detected by moving the product longitudinally past a sensor comprising an oscillatory circuit 11 whose resonance frequency varies in dependence on the presence or absence of the product and detecting the resonance frequency of variation in the resonance frequency of the oscillatory circuit 11. The oscillatory circuit controls the frequency of a square wave oscillator 12, the output of which is filtered at 13 and converted at 14 into a signal whose voltage is a function of the frequency. The latter signal is compared with a reference signal from 15 at 17 to trigger optical coupling output stage 19. The sensor may comprise a coil through which the product passes or an annular or U- shaped core provided with a winding, the product passing through an air gap. The sensor head may be water cooled.