Communications – electrical: acoustic wave systems and devices – Echo systems – Distance or direction finding
Patent
1977-07-22
1979-10-09
Farley, Richard A.
Communications, electrical: acoustic wave systems and devices
Echo systems
Distance or direction finding
73290V, 367108, 367908, G01S 968, G01F 2300
Patent
active
041707656
ABSTRACT:
A method and apparatus for indicating the level of liquid in a tank or the like whereby a transducer is mounted on a pipe above the liquid for producing, in response to a trigger signal, an ultrasonic pulse which is transmitted toward and reflected to the transducer first from a calibration target in the pipe above the liquid and then from the liquid so that the transducer produces echo pulses in response to receipt thereof. In one embodiment the calibration echo signal is applied to a logic circuit together with the output of a counter which is incremented to a predetermined count following the trigger signal by pulses from a voltage controlled oscillator so that the logic produces a control signal indicating the difference in time between when the calibration echo is received and when the counter reaches its predetermined count and which event occurs first. The logic then varies the frequency of the oscillator to reduce the difference. A further counter is enabled upon receipt of the calibration echo signal to accumulate a count of pulses from the oscillator and disabled upon receipt of the liquid echo signal so that the count indicates the liquid level.
REFERENCES:
patent: 2713263 (1955-07-01), Turner
patent: 2753542 (1956-07-01), Rod et al.
patent: 2787160 (1957-04-01), Van Valkenburg
patent: 3184969 (1965-05-01), Bolton
patent: 3394589 (1968-07-01), Tomioka
patent: 3486368 (1969-12-01), Brech
Austin James W.
Morris Oscar L.
Rothrock Michael E.
Farley Richard A.
Marvtek, Corporation
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