Sonic flow meter

• US 5,012,449 A
• Filed: 06/30/1989
• Issued: 04/30/1991
• Est. Priority Date: 06/30/1989
• Status: Expired due to Fees

• Current Assignee: Ferranti ORE Incorporated, Ultra Creative Corporation (Transcontinental Incorporated)
• Original Assignee: Ferranti ORE Incorporated
• Inventors: Todd, John D.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/374,265
• Time in Patent Office: 669 Days
• Field of Search: 367/89, 367/900, 73/861.18, 73/861.27, 73/861.28, 73/861.29, 73/861.31, 73/195, 73/24, 73/40.5 A, 364/510
• US Class Current: 367/89
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
• CPC Class Codes: Y10S 367/90 Sonar time varied gain control systems

Abstract

A gain-controlled amplifier (24) in a sonic flow meter accepts an output signal from each transducer of a plurality of pairs of transducers (1a, 1b; 2a, 2b; 3a, 3b; and 4a, 4b) in sequence. A ramp generator (62) generates a time-varying-gain output, which increases between the transmission of a pulse by one transducer and the reception thereof by another. This time-varying-gain signal is one component of the amplifier'"'"'s gain-control signal, which includes as another component an AGC value fetched from a memory (50) and rendered into analog form by a digital-to-analog converter (42). The value in the memory (50) is the difference between the time-varying-gain value and the value that other circuitry (30, 36) has determined to be necessary by monitoring the amplifier output produced during a previous operation of the same transducer pair. A third component of the gain-control signal is provided by further circuitry (40, 72, 76, 102), which acts to reduce the gain-controlled value if it determines that noise is present. It concludes that noise is present if the receiving transducer produces signal magnitudes that exceed a predetermined threshold before sound is expected from a transmitting transducer.

Claims

1. A flow meter comprising:

(A) a plurality of sonic transducers, at least a plurality of which are operable as transmitting transducers and at least a plurality of which are operable as receiving transducers, transducers, each of the transmitting transducers being operable to transmit sonic pulses along a different sonic path associated therewith through a fluid to an associated receiving transducer, each receiving transducer responding to the reception of a sonic pulse to generate a transducer output representative thereof;

(B) a driver for alternately driving each transmitting transducer individually to transmit sonic pulses along the sonic path associated therewith, each sonic pulse transmission defining the beginning of a new cycle of operation;

(C) an amplifier, having an output port, a gain-control port adapted to receive a gain-control signal, and an input port adapted to receive an amplifier input, for amplifying the amplifier input with a gain determined by the gain-control signal to generate an amplifier output;

(D) means for selectively coupling the amplifier input port to receive the transducer output of the receiving transducer associated with the sonic path associated with the transmitting transducer currently being driven by the driver;

(E) an AGC circuit responsive to the amplified signal to generate therefrom an AGC signal representing an AGC value associated with the path taken by the sonic pulse from which the amplified signal resulted;

(F) memory means responsive to the AGC signal to store the AGC value represented thereby separately from each AGC value associated with another path;

(G) means for (i) retrieving from the memory means, for use during a given cycle of operation in which the driver drives a given transmitting transducer, the AGC value represented by the AGC signal during a previous cycle in which the driver drove the given transmitting transducer and (ii) generating a retrieved-value signal from the retrieved AGC value;

(H) a TVG circuit for generating a TVG signal that changes monotonically during a time interval between the time at which the driver sends a pulse and the time at which a receiving transducer receives it;

(I) gain-control means responsive to the retrieved-value signal for generating a gain-control signal dependent thereon and applying the gain-control signal to the gain-control port of the amplifier during the given cycle of operation, the gain-control means also being responsive to the TVG signal so that the gain-control signal depends on both the TVG signal and retrieved-value signal; and

(J) measurement means responsive to the amplifier output for measuring the time intervals between transmission of sonic pulses and reception thereof, for comparing the time intervals for different paths, for computing therefrom the flow rate of the fluid flowing through the paths, and for generating an indication of the flow rate.

2. A flow meter as defined in claim 1 wherein the amplitude of the gain-control signal generated by the gain-control means is proportional to the sum of values proportional to the amplitudes of the retrieved-value signal, the TVG signal, and a constant.

3. A sonic flow meter comprising:

(A) a plurality of sonic transducers, at least a plurality of which are operable as transmitting transducers and at least a plurality of which are operable as receiving transducers, each of the transmitting transducers being operable to transmit sonic pulses along a sonic path associated therewith through a fluid to an associated receiving transducer, each receiving transducer responding to the reception of a sonic pulse to generate a transducer output representative thereof.

(B) a driver for driving a transmitting transducer to transmit sonic pulses of a predetermined frequency along the sonic path associated therewith;

(C) an amplifier, connected to receive a transducer output, for amplifying the transducer output to produce an amplified signal therefrom;

(D) a first zero-cross detector for monitoring the amplified signal and generating a first crossing signal when the amplified signal crosses from a first polarity to an opposite polarity;

(E) a second zero-cross detector for monitoring the amplified signal and generating a second crossing signal when the amplified signal crosses back from the opposite polarity to the first polarity;

(F) a window generator responsive to the first and second crossing signals for establishing a time window that brackets a point in time delayed by one-half cycle of the predetermined frequency from a zero crossing detected by the first zero-cross detector and generating a receive signal in response to the second crossing signal only if the second crossing signal occurs during the time window; and

(G) processing means for measuring the time between the sound transmission and the receive signal for a plurality of paths, computing therefrom the flow rate of the medium, and producing an indication thereof.

4. A flow meter comprising:

(A) a plurality of sonic transducers, at least a plurality of which are operable as transmitting transducers and at least a plurality of which are operable as receiving transducers, each of the transmitting transducers being operable to transmit sonic pulses along a different sonic path associated therewith through a fluid to an associated receiving transducer, each receiving transducer responding to the reception of a sonic pulse to generate a transducer output representative thereof;

(B) a driver for alternately driving each transmitting transducer individually to transmit sonic pulses along the sonic path associated therewith, each sonic pulse transmission defining the beginning of a new cycle of operation;

(C) an amplifier, having an output port, a gain-control port adapted to receive a gain-control signal, and an input port adapted to receive an amplifier input, for amplifying the amplifier input with a gain determined by the gain-control signal to generate an amplifier output;

(D) means for selectively coupling the amplifier input port to receive the transducer output of the receiving transducer associated with the sonic path associated with the transmitting transducer currently being driven by the driver;

(E) an AGC circuit responsive to the amplified signal to generate therefrom an AGC signal representing an AGC value associated with the path taken by the sonic pulse from which the amplified signal resulted;

(F) memory means responsive to the AGC signal to store the AGC value represented thereby separately from each AGC value associated with another path;

(G) means for (i) retrieving from the memory means, for use during a given cycle of operation in which the driver drives a given transmitting transducer, the AGC value represented by the AGC signal during a previous cycle in which the driver drove the given transmitting transducer and (ii) generating a retrieved-value signal from the retrieved AGC value;

(H) gain-control means responsive to the retrieved-value signal for generating a gain-control signal dependent thereon and applying the gain-control signal to the gain-control port of the amplifier during the given cycle of operation;

(I) measurement means responsive to the amplifier output for measuring the time intervals between transmission of sonic pulses and reception thereof, for comparing the time intervals for different paths, for computing therefrom the flow rate of the fluid flowing through the paths, and for generating an indication of the flow rate;

(J) a noise detector, responsive to the amplifier output, for determining whether the amplifier output, during a predetermined time interval before a receiving transducer is expected to receive a pulse from a given path, exceeds a predetermined threshold and for generating a noise signal if it does; and

(K) means responsive to the noise signal to store in the memory, in place of the current value associated with the given path, a value that represents a lower gain.