Oscillators – Automatic frequency stabilization using a phase or frequency... – With intermittent comparison controls
Patent
1981-01-26
1983-01-11
Grimm, Siegfried H.
Oscillators
Automatic frequency stabilization using a phase or frequency...
With intermittent comparison controls
310336, 331 25, 331 65, 331155, 340675, H03L 708, B65H 712
Patent
active
043684386
ABSTRACT:
In an ultrasonic system for detecting and distinguishing between superimposed and single sheets moving along a transport path, the frequency of the ultrasonic source is kept tuned to the natural frequency of the total system so that the phase displacement detected when a sheet-like object is present between the source and the ultrasonic receiver represents characteristics of the object itself. When no sheet-like object is present the receiver and the source are connected in a feedback circuit producing a certain natural frequency comparable to that which occurs with proximities between a microphone and a loud speaker, and the frequency of an oscillator is tuned to this natural frequency. When a sheet-like object is present the tuned oscillator frequency is applied to the ultrasonic source and its phase is compared with the phase of the ultrasonic signal at the receiver.
REFERENCES:
patent: 3392349 (1967-02-01), Bartley
patent: 3646372 (1972-02-01), Snellman et al.
patent: 3967143 (1976-06-01), Watanabe et al.
patent: 4066969 (1978-01-01), Pearce et al.
Grimm Siegfried H.
Johnston Albert C.
Oce'-Nederland, B.V.
Wiens Tim A.
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