GB938385A - Improvements in or relating to vibration recording apparatus - Google Patents

Abstract

938,385. Measuring vibration electrically. WAYNE KERR LABORATORIES Ltd., and R. CALVERT. March 14, 1962 [Dec. 14, 1960], No. 42995/60. Class 37. [Also in Group XXXVIII] The vibrations at different parts of a vehicle are measured with a fixed counter-electrode, to modulate each of its own carrier frequency, and the signals are fed to a tape recorder, being subsequently reproduced and separated. As shown, an earthed member 14 whose vibrations are to be measured, forms one electrode of a capacitor, the other electrode 15 being surrounded by a guard plate 16. The capacitor 14, 15 is connected in the negative feedback path of a high-gain amplifier 18 fed from a constant current generator 20, whereby the current through capacitor 14, 15 is also constant, and the voltage output from amplifier 18 is proportional to the spacing between electrodes 14, 15. This amplitude-modulated signal voltage is combined at 31 with similar signals of different carrier frequencies derived from separate transducers 11, 12, and fed to a taperecording head 27. The tape 24 has prerecorded on it the three carrier frequencies combined on one track, which are read off at 25 and separated into the individual frequencies by filters 28, 29, 30, each controlling its constant current generator 20. Specifications 863,397 and 912,041 are referred to.