Communications – electrical: acoustic wave systems and devices – Echo systems – Returned signal used for control
Patent
1998-05-01
1999-08-24
Pihulic, Daniel T.
Communications, electrical: acoustic wave systems and devices
Echo systems
Returned signal used for control
367908, G01S 1502
Patent
active
059432942
ABSTRACT:
A vibrating probe for detecting a threshold level within a vessel of fluent material, particularly a liquid, includes: an ultrasonic acoustic transducer assembly comprising a transducer element having a natural resonant frequency, and loading elements effective to shift that frequency to an effective resonant frequency of the assembly, the assembly being supported within the vessel and including a coupling member to couple the transducer acoustically to liquid reaching the threshold level, a transmitter generating pulses applied to the transducer element for repeatedly exciting the transducer element to cause the transducer assembly to resonate at its effective resonant frequency, a circuit for measuring the effective resonant frequency of the transducer over a ringdown period following cessation of each pulse, and a circuit for comparing the effective resonant frequency measured during the ringdown period following each pulse with a predetermined threshold level. The threshold level is selected so as to distinguish between the effective resonant frequency of the assembly in free air and a lower effective resonant frequency when coupled to fluent material through the coupling member. The damping effect of the fluent material, particularly if a viscous liquid, may accelerate the ringdown to an extent such that vibration is effectively suppressed before the end of the frequency measurement, thus further depressing the apparent measured frequency.
REFERENCES:
patent: 4540981 (1985-09-01), Lapetina
patent: 4831565 (1989-05-01), Woodward
patent: 5748562 (1998-05-01), Cherek et al.
patent: 5836192 (1998-11-01), Getman et al.
Bleszynski Stanislaw
Cherek Bogdan
Milltronics Ltd.
Pihulic Daniel T.
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