TRANSDUCER FOR MEASURING THE VELOCITY OR DISPLACEMENT OR BOTH OF FERROMAGNETIC MATERIAL

摘要

T I T L EA TRANSDUCER FOR MEASURING THE VELOCITY OR DISPLACEMENTOR BOTH OF FERROMAGNETIC MATERIALI N V E N T O RCORNELIS M.G. ZWARTSABSTRACT OF THE DISCLOSUREA transducer for measuring the velocity anddisplacement of ferromagnetic materials comprising first andsecond magnetic read-heads positioned close to but notcontacting the magnetic element whose velocity is to be mea-sured with the two read-heads located a fixed distance apartin the direction of travel of the element, magnetic meanspositioned close to the magnetic element ahead of the firstand second read-heads in the direction of travel of themagnetic element for increasing the magnetic surface noiselevels of the material or the magnetic element, amplifiersconnected to the two read-heads for amplifying the randomvoltage noise signals induced in the read-heads, said signalsbeing substantially identical with one being delayed in timewith respect to the other, zero-crossing detectors connectedto the outputs of the amplifiers, means for correlating thenoise signals obtained from the zero-crossing detectors andproviding an output frequency signal, an electronic digitaldelay line circuit connected between the zero-crossing detectorof the first read-head and the means for correlating the noisesignals, feedback means for applying the output frequency signalto the electronic digital delay line circuit to controlthe amount of delay such that it is equal to the physical delayproduced in the signal from the second read-head, said delaybeing related to the velocity of the magnetic element, andmeans for measuring the frequency or number or both of thecycles of the output frequency signal to give an indicationof the relative velocity or displacement or both of the magneticelement.