Ultrasonic liquid level meter

• US 4,470,299 A
• Filed: 01/04/1982
• Issued: 09/11/1984
• Est. Priority Date: 01/04/1982
• Status: Expired due to Term

• Current Assignee: BankAmerica Business Credit, Inc. (Bank of America Corp.)
• Original Assignee: Fischer & Porter Comapny
• Inventors: Soltz, Daniel J.
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US06/337,082
• Time in Patent Office: 981 Days
• Field of Search: 73/290 V, 73/597, 73/609, 73/215, 367/908, 367/108
• US Class Current: 73/290.00V
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01S 2007/52014 involving a reference reflector integrated in the sensor or transducer configuration
• CPC Class Codes: Y10S 367/908 Material level detection, e.g. liquid level

Abstract

An ultrasonic echo-ranging system adopted to measure the level of liquid in an open channel or other liquid container. The system includes an ultrasonic transducer disposed at a fixed position directly above the liquid surface, the nature of the gaseous environment therebetween determining the velocity of ultrasonic energy propagated therethrough. The transducer is excited to emit periodic pulses which are directed along a center path toward the liquid surface and reflected to produce liquid echo pulses which return to the transducer and are detected thereby. A reference reflector at a predetermined position relative to the transducer intercepts energy from a side path in the radiation pattern of the transducer to return it to the transducer to produce reference echo pulses. Means are provided to determine the transit time of pulses along the center path, and also to determine the transit time along the side path. The ratio of the reference side path and center path transit times is computed to provide an output representing the level of liquid independent of changes in the gaseous environment.

Claims

1. An ultrasonic echo-ranging system to measure the level of a liquid in an open channel or other liquid container located in a gaseous environment subject to changes which affect the velocity of acoustic propagation;

said system comprising;

(A) an ultrasonic transducer disposed at a fixed position directly above the liquid;

the gaseous environment therebetween determining the velocity of ultrasonic energy propagated therethrough;

(B) means to excite the transducer to emit periodic pulses of ultrasonic energy which are directed toward the surface of the liquid and reflected thereby to produce liquid echo pulses which return to the transducer and are detected thereby, said transducer having a radiation field pattern that includes a center path normal to the liquid surface and a side path which diverges from normal;

(C) reference means at a fixed position relative to the transducer to intercept energy from said side path and to return it to the transducer to produce reference echo pulses, said reference means being constituted by a reflector placed in said side path;

(D) receiver means coupled to the transducer to derive therefrom at separate outputs the liquid echo pulses representing center path reflection and the reference echo pulses representing side path reflection, said receiver means including means to exclude liquid echo pulses except pulses from the center path;

(E) measuring means coupled to said separate outputs to measure the time elapsed between the emitted transducer pulse and a subsequent reference echo pulse along the side path to determine the reference transit time, and to measure the time elapsed between the emitted transducer pulse and a subsequent liquid echo pulse along the center path to determine the center path transit time; and

(F) computer means coupled to the measuring means to calculate the ratio of the reference and center path transit times and to yield an output representing the level of the liquid independent of changes in the gaseous environment.

2. A system as set forth in claim 1, wherein said receiver means operated in conjunction with a pulse processor which provides one window to pass only said reference echo pulse and another window to pass only said liquid echo pulse.

3. A system as set forth in claim 1, wherein said reference means is constituted by a deflector placed in said side path to deflect the energy intercepted thereby toward a reflector placed outside of said pattern, said reflector returning the energy to the transducer.

4. A system as set forth in claim 1 wherein said computer means is a microprocessor.

5. A system as set forth in claim 1, wherein said means to measure the elapsed time includes a pulse generating clock which is started at a point coincident in time with the emitted pulse and which is stopped at a point coincident with an echo pulse.