Flowmeter system with digital phase shifter and calibration

Claim 2

A flowmeter system comprising, in combination: transducer means for transmitting acoustic compression waves upstream and downstream in a fluid flowing in a path in response to transmit signals; circuit means for measuring the phase difference between the transducer means in the fluid flow path of the acoustic compression waves transmitted upstream and circuit means for measuring the phase difference between said transducer means in the fluid flow path of the acoustic compression waves transmitted downstream; circuit means for producing a difference signal dependent on the difference between the two phase differences, the magnitude and sign of which being directly related to the instantaneous fluid flow rate and its direction; circuit means for automatically adjusting the frequency of the acoustic compression waves to a frequency where a fixed wavelength distance, in the fluid flow medium, occurs across the path of the transducer means; and digital means for generating calibration signals connected to said means for adjusting the frequency of the acoustic compression waves so as to simulate fluid flow in said path in response to signals from said transducer means and said means for adjusting the frequency of the acoustic compression waves for adjusting the phase of the transmit signals during initial calibration of the system to compensate for variations in transducer elements and to calibrate the system for use without the need of a flow in said path.

Claim 3

The flowmeter system as claimed in claim 1 wherein said adjusting and calibrating means is connected to the output of said circuit means for automatically adjusting the frequency of the compression waves and wherein the output signals therefrom are divided down into submultiple signals representing degrees of phase of the transmitted signals to be applied to a transducer, and means for selecting which phase is to be applied to said transducer to simulate flow in said path.

Claim 4

The flowmeter system as claimed in claim 1 wherein said automatic frequency adjusting means is a voltage controlled oscillator which generates output signals at a frequency depending on a voltage applied thereto, means connected to the output of said oscillator for dividing down the frequency of said output to selected signals which are submultiples of said frequency, a shift register, means for storing said submultiple signals in said shift register, means for changing said output signals into two frequency signals 180° out of phase from the other and applying said two frequency signals as a clock source to said shift register for shifting said submultiple signals out of said shift register, multiplexing means connected to the shift register, and means for selectively actuating said multiplexing means to direct which of said submultiple signals is to be directed as a phase shift signal to said transducer.

Claim 5

A flowmeter system for measuring a fluid along a path comprising in combination: means defining a path for confining a fluid flow; a first and second transducer disposed along said path; a transducer control circuit coupled to said first and said second transducers to cause said first transducer to produce first acoustic compressions in the fluid and said second transducer to produce a first received signal when said first acoustic compressions are sensed thereby during a first transmit-receive cycle and to cause said second transducer to produce second acoustic compressions in the fluid and said first transducer to produce a second received signal when said second acoustic compressions are sensed thereby during a second transmit-receive cycle; said control circuit including: means to switch from said first to said second transmit-receive cycle; first measurement means to measure a first phase difference comprising the phase difference between the first acoustic compression produced at said first transducer and said first received signal produced by said second transducer during each said first transmit-receive cycle; second measurement means to measure a second phase difference comprising the phase difference between the second acoustic compression produced at said second transducer and said second received signal produced by said first transducer during each second transmit-receive cycle; difference means responsive to said first and said second measurement means to produce a difference signal whose magnitude equals the difference between one said first phase difference and one said second phase difference wherein the magnitude of said difference signal is directly related to the instantaneous fluid flow rate and the algebraic sign of said difference signal represents the direction of fluid flow along the path; means to automatically adjust the frequency of the acoustic compressions produced by each said transducer to a frequency where a fixed wavelength distance in the fluid flow medium occurs across the distance of either said transducer, thereby maintaining operation at the acoustic resonance to maximize the magnitude of the received signal produced at the other transducer so that said difference signal output of the meter is insensitive to the velocity of sound in the fluid; and digital means connected to and responsive to said automatic frequency adjusting means for generating a plurality of signals each of which are shifted in phase with respect to the frequency of the automatic frequency adjusting means, and means for selecting which of said plurality of signals are used for adjusting the phase of the first and second acoustic compressions during a no flow condition.

Claim 6

A flowmeter system for measuring a fluid along a path comprising in combination: means defining a path for confining a fluid flow; a first and second transducer disposed along said path; a transducer control circuit coupled to said first and said second transducers to cause said first transducer to produce first acoustic compressions in the fluid and said second transducer to produce a first received signal when said first acoustic compressions are sensed thereby during a first transmit-receive cycle and to cause said second transducer to produce second acoustic compressions in the fluid and said first transducer to produce a second received signal when said second acoustic compressions are sensed thereby during a second transmit-receive cycle; said control circuit including: means to switch from said first to said second transmit-receive cycle; first measurement means to measure a first phase difference comprising the phase difference between the first acoustic compression produced at said first transducer and said first received signal produced by said second transducer during each said first transmit-receive cycle; second measurement means to measure a second phase difference comprising the phase difference between the second acoustic compression produced at said second transducer and said second received signal produced by said first transducer during each second transmit-receive cycle; difference means responsive to said first and said second measurement means to produce a difference signal whose magnitude equals the difference between one said first phase difference and one said second phase difference wherein the magnitude of said difference signal is directly related to the instantaneous fluid flow rate and the algebraic sign of said difference signal represents the direction of fluid flow along the path; means to automatically adjust the frequency of the acoustic compressions produced by each said transducer to a frequency where a fixed wavelength distance in the fluid flow medium occurs across the distance of either said transducer, thereby maintaining operation at the acoustic resonance to maximize the magnitude of the received signal produced at the other transducer so that said difference signal output of the meter is insensitive to the velocity of sound in the fluid; and digital means connected to and responsive to said automatic frequency adjusting means for generating a plurality of signals each of which are shifted in phase with respect to the frequency of the automatic frequency adjusting means, and means for selecting which of said plurality of signals are used for adjusting the phase of the first and second acoustic compressions during a no flow condition.

Claim 7

The flowmeter as claimed in claim 4 wherein said digital means comprises, a shift register with multiple output means for applying the output of said automatic frequency adjusting means to said shift register as two out-of-phase clock signals, means for dividing the output of said automatic frequency adjusting means into signals of lesser frequency and storing the latter in said shift register, said clock signals shifting said signals of lesser frequency out of said multiple outputs.

Claim 8

The flowmeter system as claimed in claim 5 wherein said selecting means is a switch operated multiplexer.

Claim 9

The flowmeter system as claimed in claim 6 wherein said selected signal is digital and circuitry is provided between said multiplexer and said transducer for changing said digital signal into an analog signal.

Claim 10

The flowmeter system as claimed in claim 7 wherein said automatic frequency adjusting means is a voltage controlled oscillator.

Claim 11

A flowmeter system comprising: means defining a path for confining the flow of a fluid medium therethrough, first and second transducers disposed along said flow path and connected to circuitry which includes a voltage controlled oscillator and a switching means for alternately generating and receiving acoustic compression waves in the fluid medium by and between the transducers and means for generating a signal in response to the received acoustic compression waves, said circuitry being of the phase lock loop type and further including, phase detector means for measuring the phase difference between the transmitted acoustic compression waves and the received acoustic compression waves, means connected to said phase detector means for producing a sum signal and a difference signal dependent upon the measured phase difference, said sum signal being transmitted to said voltage controlled oscillator for adjusting the frequency of the acoustic compression waves to maintain the length of said waves constant in the fluid medium as a measure of fluid density, means responsive to said difference signal for generating signals representing the direction and magnitude of the flow of the fluid medium, and digital means connected to and responsive to said voltage controlled oscillator for generating signals at phases different from the phase of the voltage controlled oscillator and applying said signals to said transducers to simulate flow of fluid without the need of an actual flow of fluid in said path to calibrate said system.

Claim 12

A flowmeter system comprising: means defining a path for confining the flow of a fluid medium therethrough, first and second transducers disposed along said flow path and connected to circuitry which includes a voltage controlled oscillator and a switching means for alternately generating and receiving acoustic compression waves in the fluid medium by and between the transducers and means for generating a signal in response to the received acoustic compression waves, said circuitry being of the phase lock loop type and further including, phase detector means for measuring the phase difference between the transmitted acoustic compression waves and the received acoustic compression waves, means connected to said phase detector means for producing a sum signal and a difference signal dependent upon the measured phase difference, said sum signal being transmitted to said voltage controlled oscillator for adjusting the frequency of the acoustic compression waves to maintain the length of said waves constant in the fluid medium as a measure of fluid density, means responsive to said difference signal for generating signals representing the direction and magnitude of the flow of the fluid medium, and digital means connected to and responsive to said voltage controlled oscillator for generating signals at phases different from the phase of the voltage controlled oscillator and applying said signals to said transducers to simulate flow of fluid without the need of an actual flow of fluid in said path to calibrate said system.