Acoustic oscillator fluid velocity measuring device

• US 4,003,256 A
• Filed: 11/17/1975
• Issued: 01/18/1977
• Est. Priority Date: 11/17/1975
• Status: Expired due to Term

• Current Assignee: Her Majesty The Queen In Right of Canada As Represented By The Minister of National Defence
• Original Assignee: Canadian Patents and Development Limited
• Inventors: White, Bryan F., Donelan, A. Mark
• Primary Examiner(s): Ruehl, Charles A.
• Application Number:
  US05/632,802
• Time in Patent Office: 428 Days
• Field of Search: 73/194 A, 73/560, 73/67.6
• US Class Current: 73/861.27
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01P 5/247 Sing-around-systems

Abstract

A fluid velocity measuring device for the accurate fast measurement of the velocity of a fluid whether liquid or gas using the time of passage of acoustic energy through the fluid as the frequency determining element in a continuous wave oscillator. The frequencies or periods of oscillations of two anti-parallel acoustic paths are used to compute fluid velocity between the electro-acoustic transducers at the ends of the acoustic paths. The device in accordance with this invention may utilize a single reversing acoustic path or two anti-parallel acoustic paths. The velocity resolution can be selected by the operator in accordance with a stated uncertainty principle limiting the ratio of frequency response to velocity resolution. Mode ambiguities due to fluid phase velocity variations are avoided by varying the path lengths. The frequency range of the oscillator is limited by a phase locked loop.

Claims

1. A fluid velocity measuring device comprising:

a free running continuous wave acoustic oscillator having a first and second acoustic transducer defining an acoustic path within the fluid and switching means coupled to the first and second transducer to periodically reverse the direction of acoustic energy propagation between the transducers, said acoustic path being the frequency determining element of the oscillator;

means for detecting the output signals of the oscillator as it propagates energy in a first direction in said fluid and in a second direction opposite the said first direction;

up/down counter means having the down terminal coupled to the oscillator signal detecting means;

reference oscillator means coupled to the up terminal of the counter;

switch means for coupling the output of the counter to first and second latching circuit means;

sequencer means for controlling said switch means to store the count from the counter means in said first latch means when the acoustic energy is propagated in a first direction, and in said second latch means when the acoustic energy is propagated in a second direction; and

logic means coupled to the first and second latch means to compute the fluid velocity as a function of the difference of the counts stored in said first and second latch means.

2. A fluid velocity measuring device comprising:

a free running continuous wave acoustic oscillator having a first and second acoustic transducer defining an acoustic path within the fluid and switching means coupled to the first and second transducer to periodically reverse the direction of acoustic energy propagation between the transducers, said acoustic path being the frequency determining element of the oscillator;

means for detecting the output signals of the oscillator as it propagates energy in a first direction in said fluid and in a second direction opposite the said first direction;

a first counter means coupled to the oscillator signal detecting means for providing an output signal after a predetermined count η

;

reference oscillator means having an output frequency which is a multiple of the acoustic oscillator frequency;

second counter means coupled to said reference oscillator means for counting the reference oscillator signal, said second counter means being coupled to said first counter means to hold upon receipt of the output signal from the first counter; and

processor means for receiving sequential counts of said second counter means which represent the period of the oscillator when acoustic energy is propagated in a first direction and in the opposite direction, the processor means further adjusting said counts to compensate for oscillator circuit electronic delay and computing the fluid velocity as a function of the difference of the inverse of the adjusted counts.

3. A fluid velocity measuring device comprising:

a first free running continuous wave acoustic oscillator having a first send and a first receive acoustic transducer for defining a first acoustic path therebetween in the direction of fluid flow, said first acoustic path being the frequency determining element of the first oscillator;

a second free running continuous wave acoustic oscillator having a second send and a second receive acoustic transducer for defining a second acoustic path therebetween in the opposite direction of fluid flow, said second acoustic path being the frequency determining element of the second oscillator;

first means for detecting the output signal of the first oscillator as it propagates energy in the direction of fluid flow;

second means for detecting the output signal of the second oscillator as it propagates energy in the opposite direction of fluid flow;

first and second counter means coupled to the first and second oscillator signal detecting means respectively for providing output signals after a predetermined count η

;

reference oscillator means having an output frequency which is a multiple of the acoustic oscillator frequency;

third and fourth counter means having their inputs coupled to said reference oscillator means, the third counter being coupled to said first counter means to hold upon receipt of the first counter output signal, the fourth counter being coupled to said second counter means to hold upon receipt of the second counter output signal; and

processor means for receiving the counts of said third and fourth counter means, adjusting said counts to compensate for oscillator circuit electronic delays and computing the fluid velocity as a function of the difference of the inverse of the adjusted counts.