Apparatus for non-contact measurement of distance from a metallic body using a detection coil in the feedback circuit of an amplifier

摘要

Apparatus for non-contact measurement of the distance between a detecting coil and a metallic body mounted in confronting relation thereto comprising a differential amplifier to one terminal of which is connected a reference oscillator and to the other terminal of which is connected a feedback circuit. The feedback circuit incorporates the detecting coil and the amplified differential output signal between the AC signals applied to the differential amplifier and the signal supplied to the differential amplifier resulting from the impedance of the detecting coil corresponding to the distance between the detecting coil and the metallic body are thus a measure of the distance. At least one of the parameters of open-loop gain of the differential amplifier and the amount of feedback in the feedback circuit is pre-determined so as to linearize at least for a pre-determined measuring range the output characteristics of the differential amplifier resulting from the variation of the detecting coil impedance caused by the variation of the distance.