US 4,821,569 AGranted

Parasitic echo pulse rejector for ultrasonic liquid level meter

AssigneeFischer & Porter Co.

InventorDaniel J. Soltz

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Abstract

An ultrasonic echo-ranging meter for measuring the changing level of liquid in a tank or open channel, the meter including a transducer at a raised position above the liquid surface. Pulses of ultrasonic energy transmitted by the transducer are directed toward the liquid surface and reflected thereby to produce main echo pulses that are picked up by the same transducer. The round trip transmit time of the pulse energy in the gaseous medium above the liquid depends on the distance between the transducer and the liquid surface, this time being measured to provide a reading of liquid level. Also intercepted by the transducer are parasitic echo pulses originating from reflecting wall surfaces and other obstacles in the vicinity of the tank or channel, which parasitic pulses may be confused with the main echo pulses and result in an erroneous reading. In order to reject these parasitic pulses without appreciably slowing down the response time of the meter to liquid level changes, means are provided that discriminate between parasitic and main echo pulses and act to render the meter insensitive to parasitic pulses.

Claims9

Dependent claims

An ultrasonic echo-ranging system to measure within a predetermined time span the level of liquid in an open channel or tank, said system comprising:

A an ultrasonic transducer disposed on an ultrasonically-reflective surface at a fixed raised position above the surface of the liquid;
B means to excite the transducer to emit periodic pulses of ultrasonic energy which are propagated in a gaseous medium between the transducer and the liquid and are directed toward the surface of the liquid and reflected from this target to produce main echo pulses which return to the transducer and are detected thereby, said transducer also detecting parasitic echo pulses originating from said ultrasonically-reflective surface;
C means including a programmed microcomputer and a distance counter responsive to pulses detected by the transducer to measure the round trip transit time of the pulse energy in the gaseous medium to provide a reading of liquid level;
and
D a parasitic echo rejector operatively coupled to said microcomputer acting to discriminate between said main echo pulses and said parasitic pulses received within said span to render said system non-responsive to said parasitic pulses to provide an accurate reading of liquid level.

2 more elements

Dependencies are inferred from the claim text.