US 5,131,271 AGranted

Ultrasonic level detector

AssigneeMagnetrol International, Incorporated

InventorsKevin M. Haynes, Steven E. Margison

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Abstract

An ultrasonic level detector includes a transducer for generating and receiving bursts of sonic energy at a surface to locate the position of the surface. In response to receiving a burst of energy reflected from the surface, the transducer generates an electrical signal, which is then supplied to a variable gain amplifier. After amplification, the electrical signal is supplied to a comparator and a peak detector. The comparator generates a timing signal upon the electrical signal exceeding a threshold. A window generator circuit generates a receive window that controls whether the electrical signal is supplied to the comparator and the magnitude of the threshold on the comparator. The peak detector determines the maximum amplitude of the electrical signal, which may be used to vary the amplifier gain and the number of pulses included in an excitation signal which drives the transducer. Upon receipt of the timing signal, a microprocessor determines the distance between the transducer and the detected surface.

Claims10

Dependent claims

An ultrasonic level detector for sensing the location of a surface to be detected with respect to a transducer, said level detector having a successively narrowed receive window centered about the expected time of arrival of an echo from said surface to reduce the likelihood of obtaining false indications of said surface due to noise or extraneous signals, said level detector comprising:

means for periodically generating an excitation signal;
transducer means coupled to said generating means for converting said excitation signal into a burst of energy, transmitting said burst of energy towards said surface, receiving reflected energy from said surface, and generating an electrical signal based upon the magnitude of said reflected energy;
comparator means coupled to the output of said transducer means for comparing the magnitude of said electrical signal with a threshold in order to detect an echo signal;
means for determining a receive window associated with the level of said surface, said receive window being successively narrowed and centered about the expected time of arrival of said echo from said surface,
said determining means causing said threshold of said comparator means to have a first relatively low value during said receive window and a second relatively high value outside of said receive window whereby the likelihood that spurious electrical signals generated by said transducer means are erroneously interpreted as valid echo signals is reduced;
and
means for determining the level of the surface based upon the flight time associated with said echo signal.

4 more elements

Dependencies are inferred from the claim text.