Ultrasonic fluid speed of sound and flow meter apparatus and method

Abstract

An ultrasonic speed of sound and flow metering system which may utilize only one pair of ultrasonic transducers by incorporating a unique time share feature. In one embodiment a direct synthesis of a frequency proportional to the speed of sound in a flowing medium is obtained using one voltage controlled oscillator. An additional direct synthesis of a data frequency proportional to the flow of the medium is derived from signals inversely proportional to sound energy transit times upstream and downstream.

I claim: 
     
       1. In an ultrasonic speed of sound and flow meter system of the type utilizing first and second transducers spaced in relative upstream-downstream positions in communication with the fluid to be metered, means for generating signals to be transmitted by said transducers through said fluid, means for receiving signals sensed by said transducers, means for generating a reference signal, means for comparing the phase of the received signal and the reference signal and generating a phase dependent signal, means responsive to said phase dependent signal for generating signal levels proportional to upstream and downstream speeds of sound, means responsive to said signal levels for providing frequencies proportional to upstream and downstream speeds of sound, control means utilizing said frequencies for directing transmission alternately by said first and second transducer and reception alternately by said second and first transducer respectively, and means combining said frequencies whereby a sum frequency is obtained proportional to the speed of sound in the medium and a difference frequency is obtained proportional to the flow rate of the medium. 
     
     
       2. An ultrasonic speed of sound and flow meter system as in claim 1 wherein the means providing frequencies proportional to upstream and downstream speeds of sound comprise first and second voltage controlled oscillators receiving downstream and upstream transmitted signals respectively and wherein said means combining said frequencies comprise a balanced modulator, said modulator operating to provide said sum frequency proportional to speed of sound in the medium and said difference frequency indicative of flow rate. 
     
     
       3. An ultrasonic speed of sound and flow meter system as in claim 1 wherein said means providing frequencies proportional to upstream and downstream speeds of sound and said means combining said frequencies comprise a voltage controlled oscillator, means for controlling the output frequency of the voltage controlled oscillator utilizing said speed of sound proportional signal levels to provide said frequency indicative of sound propagation speed through the medium, means for synthesizing a data frequency utilizing said speed of sound proportional signals to provide said frequency indicative of flow rate, and means combining said oscillator and data frequencies. 
     
     
       4. An ultrasonic speed of sound and flow meter system as in claim 3 together with transmit signal automatic gain control responsive to the amplitude of said received signal, and voltage comparator means responsive to a predetermined amplitude transmit signal indicating a low received signal operating to generate an alarm and to block data from said oscillator and data frequencies. 
     
     
       5. An ultrasonic speed of sound and flow meter system as in claim 3 wherein said means for controlling the output frequency of said voltage controlled oscillator comprises a summing circuit receiving said signal levels proportional to upstream and downstream speeds of sound, an integrator responsive to the output of the summing circuit, said integrator operating into said voltage controlled oscillator whereby a change is effected at said oscillator output proportional to the integral of said summing circuit output. 
     
     
       6. An ultrasonic speed of sound and flow meter system as in claim 3 wherein said means for synthesizing a data frequency utilizing said speed of sound proportional signals comprises first and second integrator circuits to receive said upstream and downstream speed of sound proportional signals, first and second comparators to receive the outputs of said first and second integrators respectively, switching means to direct the upstream frequency proportional signal alternately to said first and second integrators and actuated by said second comparator, switching means to direct said downstream frequency proportional signal alternately to said first and second integrators and actuated by the output of said first comparator, and a frequency multiplier circuit to receive the outputs of said first and second comparators to provide a frequency indicative of flow. 
     
     
       7. An ultrasonic speed of sound and flow meter system as in claim 6 together with a bi-directional flow indication actuated by phase relationship between said first and second comparators. 
     
     
       8. An ultrasonic speed of sound and flow meter system as in claim 3 wherein said means combining said oscillator and data frequencies comprises a frequency divider to receive the output of said voltage controlled oscillator, a pair of output signals in quadrature from said frequency divider, first and second balanced modulators, a pair of outputs in quadrature from said means for synthesizing a data frequency, circuit means directing said leading divider frequency and said lagging data frequency to said first balanced modulator, circuit means directing said lagging divider frequency and said leading data frequency to said second balanced modulator, linear frequency mixing means to receive the outputs of said first and second balanced modulators, said mixing means operating to provide first and second frequency outputs proportional to downstream and upstream speeds of sound respectively. 
     
     
       9. An ultrasonic speed of sound and flow meter system as in claim 1 wherein said control means utilizing said frequencies for directing transmission alternately by said first and second transducers and reception alternately by said second and first transducers respectively comprises circuit means responsive to a predetermined number of cycles of said upstream and downstream frequencies providing an up/down control, first switching means sensitive to said up/down control to alternately direct said signals to be transmitted to said first and second transducers, second and first preamplifiers receiving said signals sensed by said second and first transducers respectively, second switching means sensitive to said up/down control to direct output alternately from said second and first preamplifiers, a trigger circuit to define the phase of said received signal, said trigger circuit output directed to said means for comparing the phase of the received signal and the reference signal. 
     
     
       10. An ultrasonic speed of sound and flow meter system as in claim 1 wherein said means for comparing the phase of the received signal and the reference signal and generating a phase dependent signal comprises circuitry having first and second output and providing one of said first and second outputs dependent on phase lead or lag of said received signal relative to said referer signal and wherein said means responsive to said phase dependent signal for generating signal levels proportional to upstream and downstream speeds of sound comprises circuitry for providing a signal level having a polarity determined by said one of said first and second outputs for both upstream and downstream transmissions and for integration of said signal level having a polarity separately for both upstream and downstream transmissions. 
     
     
       11. An ultrasonic speed of sound and flow meter system as in claim 1 wherein said means for generating signals to be transmitted by said transducers and said means for receiving the signals sensed by said transducers comprise switching means for directing said transmission signals to said first transducer, circuit means for receiving and shaping a signal transmitted generally downstream, circuit means directing said shaped signal to actuate said switching means directing the subsequent transmit pulse to said second transducer for transmission generally upstream. 
     
     
       12. An ultrasonic speed of sound and flow meter system as in claim 1 together with an alarm indication providing evidence of loss of system tracking when said means for comparing the phase of the received signal and the reference signal does not display a reversal within a preset period of time to said means responsive to said phase dependent signal. 
     
     
       13. An ultrasonic speed of sound and flow meter system as in claim 1 together with a preset repetition rate proportional to upstream and downstream speeds of sound, said repetition rate providing suppression of echoes generated within the flowing medium by prior transmission pulses. 
     
     
       14. In an ultrasonic speed of sound and flow meter system of the type utilizing first and second transducers spaced in relative upstream-- downstream positions in communication with the fluid to be metered, means for alternately transmitting signals through the fluid from said first and second transducers respectively, means for receiving signals from the fluid in said second and first transducers respectively, means for generating a reference signal, means for comparing said reference signal with said received signals and generating a comparison signal, means responsive to said comparison signal for generating signals proportional to upstream and downstream transmission times, and means responsive to said last named signals for synthesizing frequencies proportional to said upstream and downstream transmission times, said synthesizing means forming a sum frequency and a difference frequency of said upstream and downstream transmission frequencies indicative of fluid sound propagation velocity and flow rate respectively. 
     
     
       15. In an ultrasonic speed of sound and flow meter system of the type utilizing first and second transducers spaced in relative upstream-downstream positions in communication with the fluid to be metered, means for alternately transmitting signals to the fluid from said first and second transducers respectively, means for receiving signals from the fluid in said second and first transducers respectively, means for generating a reference signal, and means responsive to said received and reference signals for generating frequencies proportional to the upstream and downstream speeds of sound, said frequencies combining to form a sum frequency indicative of sound propagation velocity through the fluid and a difference frequency indicative of flow rate. 
     
     
       16. A method of measuring fluid flow rate and velocity of sound propagation through a flowing fluid utilizing at least one pair of first second ultrasonic energy transducers capable of functioning as transmitters and receivers in communication with the fluid which comprises generating a transmit pulse, transmitting said transmit pulse from said first transducer through said fluid in a generally downstream direction, generating a reference pulse, receiving said transmitted pulse at said second transducer, comparing the received pulse and the reference pulse in phase and generating a signal with phase dependent polarity, connecting said signal with phase dependent polarity to a first summing network, generating a first control signal in said first summing network, alternating the direction of the subsequent transmit pulse to said second transducer with said first control signal, transmitting a subsequent transmit pulse from said second transducer through said fluid in a generally upstream direction, generating a subsequent reference pulse, receiving said subsequent transmit pulse at said first transducer, comparing the subsequent received pulse and the subsequent reference pulse in phase and generating a subsequent signal with phase dependent polarity, connecting said subsequent signal with phase dependent polarity to a second summing network, generating a second control signal in said second summing network, controlling the output of a high frequency VCO with the mean value of said first and second control signals, synthesizing a data frequency responsive to said control signals, said VCO and data frequencies providing a signal frequency proportional to the speed of sound through the medium, and a signal frequency proportional to flow rate respectively. 
     
     
       17. A method of measuring fluid flow rate and velocity of sound propagation through the fluid utilizing at least one pair of first and second ultrasonic energy transducers capable of functioning as transmitters and receivers in communication with the fluid which comprises generating a transmit pulse, generating a reference pulse, directing the transmit pulse alternately upstream and downstream of the flowing medium, receiving the transmit pulse, comparing phase of the received and reference pulses, generating a signal dependent on said phase comparison, generating signals proportional to upstream and downstream sound speeds responsive to said signal dependent on phase, summing said proportional signals, controlling a voltage controlled oscillator with said sum, generating a data frequency utilizing said proportional signals, combining said data frequency with said oscillator frequency to synthesize upstream and downstream sound speed frequencies, generating control signals responsive to said sound speed frequencies, said control signals operating to maintain a constant time relation between all system signals for varying fluid characteristics and different size flow conduits. 
     
     
       18. A method of measuring fluid flow rate and velocity of propagation as in claim 17 wherein generating a signal dependent on said phase comparison and generating signals proportional to upstream and downstream sound speeds comprises directing downstream received signals to a first channel, directing upstream received signals to a second channel, generating a pulse of one polarity for received pulse phase leading reference pulse and of opposite polarity for reference pulse phase leading received pulse, delivering said pulses in said first channel to a first integrator, delivering said pulses in said second channel to a second integrator, said integrators operating to sum pulses and to provide outputs proportional to downstream and upstream sound speeds respectively. 
     
     
       19. A method of measuring fluid flow rate and velocity of sound propagation as in claim 17 wherein generating a data frequency utilizing said proportional signals comprises directing said signals to first and second fast integrators, connecting said first and second integrators to first and second voltage comparators, directing the output of said first voltage comparator to alternately switch the upstream and downstream proportional signals to the input of said second fast integrator, directing the output of said second comparator to alternately switch the upstream and downstream proportional signals to the input of said first fast integrator, and combining said first and second comparator outputs. 
     
     
       20. A method of measuring fluid flow rate and velocity of sound propagation as in claim 19 wherein combining said first and second comparator outputs comprises multiplying the frequency at said first and second comparator outputs to provide a data frequency, and providing a constant data frequency pulse charge to facilitate data reduction. 
     
     
       21. A method of measuring fluid flow rate and velocity of sound propagation as in claim 17 wherein combining said data frequency with said oscillator frequency comprises dividing said oscillator frequency to obtain two outputs in quadrature, directing said data frequency and said divided oscillator frequency to first and second balanced modulators, mixing the outputs of said first and second modulators to obtain a sum frequency and a difference frequency of the oscillator and data frequencies whereby the balanced modulator output frequencies are proportional to upstream and downstream speeds of sound. .Iadd. 22. In an ultrasonic speed of sound and fluid flow meter system of the type utilizing first and second transducers spaced in relative upstream-downstream positions in communication with the fluid to be metered, reference means for generating a reference signal, transmitting means responsive to said reference signal for alternately transmitting signals through the fluid from said first and second transducers respectively, means for receiving signals from the fluid in said second and first transducers respectively, means for comparing in time said reference signal with said received signals and generating a comparison signal, means responsive to said comparison signal for generating signals related to upstream and downstream transmission times, and synthesizing means responsive to said last named signals for synthesizing signals related to fluid sound propagation velocity and flow rate, said reference means responsive to both said fluid sound propagation velocity and flow rate related signals for controlling the timing of said reference signal. .Iaddend. .Iadd. 23. An ultrasonic speed of sound and flow meter system as in claim 22 wherein said transmitting means also is responsive to both said fluid sound propagation velocity and flow rate related signals. .Iaddend..Iadd. 24. In an ultrasonic speed of sound and flow meter system of the type utilizing first and second transducers spaced in relative upstream-downstream positions in communication with the fluid to be metered, reference means for generating a reference signal, transmitting means responsive to said reference signal for alternately transmitting signals through the fluid from said first and second transducers respectively, means for receiving signals from the fluid in said second and first transducers respectively, and synthesizing means responsive to said received and reference signals for synthesizing signals related to fluid sound propagation velocity and flow rate, said reference means responsive to said fluid sound propagation velocity and flow rate related signals for controlling the timing of said reference signal. .Iaddend..Iadd. 25. A method of measuring fluid flow rate and velocity of sound propagation through the fluid utilizing at least one pair of first and second ultrasonic energy transducers capable of functioning as transmitters and receivers in communication with the fluid which comprises generating a transmit pulse, generating a reference pulse related in time to said transmit pulse, directing the transmit pulse alternately upstream and downstream of the flowing medium, receiving the transmitted pulse, comparing the phase of the received and reference pulses, generating signals dependent on said phase comparison and the directionality of transmission, synthesizing signals related to fluid sound propagation velocity and flow rate from said signals dependent on said phase comparison and directionality, combining said synthesized signals to provide control signals for controlling the time relations between said transmit and reference pulses separately for each of the upstream and downstream transmissions. .Iaddend.