Apparatus for indicating fluid flow velocity
First Claim
1. Apparatus for use in measuring the velocity or a component of velocity of fluid flow, which apparatus comprises first and second units spaced apart and each adapted to transmit and receive pressure wave pulses travelling over a path through the fluid in the direction in which velocity component is to be measured, variable frequency oscillator means, timing control means for defining time intervals of duration independent of the frequency of the variable frequency oscillator means, trigger means under control of the said timing control means for causing a pressure wave pulse to be transmitted from the First unit to the second unit and, separately, from the second unit to the first unit, and control means for adjusting the variable frequency oscillator means to generate a first frequency dependent upon the time taken for a pressure wave pulse to travel from the first unit to the second unit and, separately under control of said timing control means, to generate a second frequency dependent upon the time taken for a pressure wave pulse to travel from the second unit to the first unit, and a difference determining means for determining the difference between said first and second frequenices.
0 Assignments
0 Petitions
Accused Products
Abstract
Fluid flow rate is determined by transmitting ultrasonic pulses in both directions along a path through the fluid aligned with the direction in which velocity component is to be measured. Transmission of, and measurement upon, pulses in the two directions are controlled by a master clock pulse generator. The frequency of a first variable frequency oscillator is adjusted to fit N pulses exactly into the timer period for flight of an ultrasonic pulse along the path in one direction. The frequency of a second variable frequency oscillator is adjusted to fit N pulses exactly into the time period for flight of an ultrasonic pulse along the path in the opposite direction. The difference frequency is proportional to velocity component. This system may be combined with a limited sing-around system to improve resolution, at the expense of the time response.
78 Citations
29 Claims
-
1. Apparatus for use in measuring the velocity or a component of velocity of fluid flow, which apparatus comprises first and second units spaced apart and each adapted to transmit and receive pressure wave pulses travelling over a path through the fluid in the direction in which velocity component is to be measured, variable frequency oscillator means, timing control means for defining time intervals of duration independent of the frequency of the variable frequency oscillator means, trigger means under control of the said timing control means for causing a pressure wave pulse to be transmitted from the First unit to the second unit and, separately, from the second unit to the first unit, and control means for adjusting the variable frequency oscillator means to generate a first frequency dependent upon the time taken for a pressure wave pulse to travel from the first unit to the second unit and, separately under control of said timing control means, to generate a second frequency dependent upon the time taken for a pressure wave pulse to travel from the second unit to the first unit, and a difference determining means for determining the difference between said first and second frequenices.
-
2. Apparatus as claimed in claim 1, wherein the variable frequency oscillator means is controlled by the said control means to generate a number N1 of oscillations or pulses in a first time period being that taken for a pressure wave pulse to travel from the first unit to the second unit and a number N2 of oscillations or pulses in a second time period being that taken for a pressure wave pulse to travel from the second unit to the first unit, said control means comprising logic circuitry for comparing the times of occurrence of the N1th oscillation or pulse with the time of arrival of the pressure wave pulse at the second unit and for comparing the time of occurrence of the N2th oscillation or pulse and the time of arrival of the pressure wave pulse at the first unit, the said oscillation or pulse repetition frequency being adjusted to tend to bring the said times of occurrence of the N1th or N2th oscillation or pulse into coincidence with the time of arrival of the respective pressure wave pulse, the said difference determining means indicating the difference in frequency between the oscillations or pulses generated in the first time period and the oscillations or pulses generated in the second time period.
-
3. Apparatus as claimed in claim 2, wherein inhibitor means are provided for inhibiting adjustment of the oscillation or pulse repetition frequency in the event that no pressure wave pulse is received within a predetermined period embracing its expected time of arrival.
-
4. Apparatus as claimed in claim 2, wherein N1 N2 N.
-
5. Apparatus as claimed in claim 1, wherein said trigger means comprises first and second trigger devices, and first trigger control means are provided for causing said frist trigger device to re-trigger the first unit upon reception of a pulse by the second unit, and for inhibiting said first trigger device from further re-triggering when a predetermined number M1 of pulses has been transmitted from the first unit to the second unit, second trigger control means are provided for causing said second trigger device to re-trigger the second unit upon reception of a pulse by the first unit, and for inhibiting said second trigger device from further re-triggering when a predetermined number M2 of pulses has been transmitted from the second unit to the first unit, the timing control means being set to initiate pulse transmission from the second unit to the first unit only after sufficient time has elapsed for completion of M1 sing around transmissions from the first unit to the second unit and to initiate pulse transmission from the first unit to the second unit only after sufficient time has elapsed for completion of M2 sing around transmissions from the second unit to the first unit, and the variable frequency oscillator means is controlled to generate a first frequency dependent upon the time taken for M1 sing around transmissions of pressure wave pulses from the first unit to the second unit and a second frequency dependent upon the time taken for M2 sing around transmissions of pressure wave pulses from the second unit to the first unit.
-
6. Apparatus as claimed in claim 5, wherein M1 M2 M.
-
7. Apparatus as claimed in claim 1, wherein said timing control means comprises a Clock pulse generator, the frequency of which is fixed for a given set of measurement conditions.
-
8. Apparatus for use in measuring velocity or a component of velocity of fluid flow, which apparatus comprises first and second units spaced apart and each adapted to transmit and receive pressure wave pulses travelling over a path through the fluid in the direction in which velocity component is to be measured, first and second variable frequency oscillators, timing control means for defining time intervals of duration independent of the frequency of the variable frequency oscillators, means under control of the said timing control means for causing a pressure wave pulse to be transmitted from the first unit to the second unit and separately, from the second unit to the first unit, first control means for controlling the frequency of the first variable frequency oscillator to generate a first frequency dependent upon the time taken for a pressure wave pulse to travel from the first unit to the second unit, second control means for controlling the frequency of the second variable frequency oscillator to generate a second frequency dependent upon the time taken for a pressure wave pulse to travel from the second unit to the first unit, the first and second control means being controlled for operation in sequence by the timing control means, and a difference determining means for determining the difference between the said first and second frequencies.
-
9. Apparatus as claimed in claim 7, wherein the first variable frequency oscillator is controlled by the first control means to generate a number of N1 of oscillations or pulses in a first time period being that taken for a pressure wave pulse to travel from the first unit to the second unit, the second variable frequency oscillator is controlled by the second control means to generate a number N2 of oscillations or pulses in a second time period being that taken for a pressure wave pulse to travel from the second unit to the first unit, the said first and second control means each comprising logic circuitry for comparing the times of occurrence of the respective N1th or N2th oscillation or pulse with the time of arrival of the pressure wave pulse at the second unit or first unit respectively and frequency control means for adjusting the frequency of the respective variable frequency oscillator to tend to bring said time occurrence of the respective N1th or N2th pulse into coincidence with the time of arrival of the pressure wave pulse at the second unit or first unit respectively, the said difference determining means determining the difference in frequency between the oscillations or pulses generated in the first time period and the oscillations or pulses generated in the second time period.
-
10. Appparatus as claimed in claim 9, wherein inhibitor means are provided for inhibiting adjustment of the oscillation or pulse repetition frequency in the event that no pressure wave pulse is received within a predetermined period embracing its expected time of arrival.
-
11. Apparatus as claimed in claim 8, wherein N1 N2 N.
-
12. Apparatus as claimed in claim 9, wherein the said frequency control means comprises a first device operative when switched to increase the frequency of the associated variable frequency oscillator and a second device operative when switched to decrease the frequency of the associated variable frequency oscillator.
-
13. Apparatus as claimed in claim 12, wherein the logic circuitry provides an output for switching the said first device when the time of arrival of the pressure wave pulse is in advance of the time of occurrence of the respective N1th or N2th oscillation or pulse, the logic circuitry provides an output for switching the said second device when the time of occurrence of the respective N1th or N2th oscillation is in advance of the time of arrival of the pressure wave pulse anD a said pressure wave pulse arrives within a time period embracing its expected time of arrival, and the logic circuitry provides no output if no pressure wave pulse arrives within the said time period embracing its expected time of arrival.
-
14. Apparatus as claimed in claim 13, wherein the said first device when switched increases the frequency of the associated variable frequency oscillator by a fixed increment and the said second device when switched decreases the frequency of the associated variable frequency oscillator by a fixed increment.
-
15. Apparatus as claimed in claim 14, wherein means is provided for adjusting temporarily the magnitude of the said fixed increments.
-
16. Apparatus as claimed in claim 9, wherein a time reference upon received pressure wave pulses is established by a zero-crossover detector.
-
17. Apparatus as claimed in claim 9, wherein sign detector means is provided for detecting which is the greater of the frequencies of the respective first and second variable frequency oscillators, and the oscillations or pulses of the difference frequency are counted by an up/down counter set to count respectively up or down by the sign detector means according to which of the said frequencies is the greater.
-
18. Apparatus as claimed in claim 17, wherein means is provided for reversing the setting of the up/down counter when it counts down below zero.
-
19. Apparatus as claimed in claim 18, wherein means is provided for displaying a negative symbol when the setting of the up/down counter is reversed.
-
20. Apparatus as claimed in claim 9, wherein said timing control means comprises a clock pulse generator, the frequency of which is fixed for a given set of measurement conditions.
-
21. Apparatus for measuring a component of velocity of a flowing fluid comprising:
- a. first and second transducer units spaced apart relative to the fluid flow and each adapted to transmit and receive pressure wave pulses through the fluid;
b. first and second drive means connected, respectively, with said first and second transducers for causing, when energized, pressure wave pulses to be transmitted from the associated transducer to the other said transducer;
c. a clock pulse generator which is set to generate oscillations or pulses at a preselected frequency such that the time interval between oscillations or pulses is of the same order but is greater than the expected time of flight of a pressure wave pulse between said transducers;
d. first and second variable frequency oscillators connected in respective association with said first and second drive means;
e. first and second control means associated, respectively, with said first and second variable frequency oscillators for controlling the frequency of the associated oscillator so that a number N of oscillations or pulses are generated in the time taken for a pressure wave to travel from the associated said transducer unit to the other said transducer unit, said control means comprising logic circuitry for comparing, for each direction of flight, the time of occurrence of the Nth oscillation or pulse with the time of arrival of the pressure wave pulse;
f. first and second adjustment means associated, respectively, with said first and second variable frequency oscillators and responsive to said logic circuitry for adjusting the oscillation or pulse repetition frequencies of said variable frequency oscillators to tend to bring the time of occurrence of the Nth oscillations or pulses into coincidence with the time of arrival of the respective pressure wave pulse;
g. first and second gate means associated, respectively, with said clock pulse generator and said first and second control means to energize the associated drive means only when the associated one of said gates has received both an oscillation signal or pulse from said clock pulse generator and a first next oscillation or pulse from the associated one of said variable frequency oscillators;
h. first aNd second inhibit means connected respectively to the said first and second adjustment means for inhibiting adjustment of the frequency of said associated variable frequency oscillator in the event that no pressure wave pulse is received within a predetermined period embracing its expected time of arrival; and
i. a difference determining means for determining the difference in frequency between the oscillations or pulses generated by said first and second variable frequency oscillators.
- a. first and second transducer units spaced apart relative to the fluid flow and each adapted to transmit and receive pressure wave pulses through the fluid;
-
22. Apparatus according to claim 21, including delay means interposed between said clock pulse generator and one of said gate means to delay the reception of an oscillation or pulse from said clock pulse generator at that gate means.
-
23. Apparatus according to claim 22, wherein said delay means delays the reception of the clock pulse generator oscillations or pulses at said associated gate for a time period sufficiently short that the associated said transducer unit transmits a pressure pulse before it receives a previously transmitted pulse from the other said transducer unit.
-
24. Apparatus according to claim 21, including a zero-crossover detector connected to said transducer units for providing a time reference signal of the arrival of a received pressure pulse.
-
25. Apparatus according to claim 24, further including means which are governed by said clock pulse generator to selectively switch the output of said zero-crossover detector to either of said control means.
-
26. Apparatus according to claim 21, wherein an automatic gain controlled amplifier means is provided to amplify the input signal to said zero-crossover detector to a substantially constant level.
-
27. Apparatus according to claim 21, wherein said transducer units are spaced apart along a common boundary of the fluid flow.
-
28. Apparatus for use in measuring the velocity or a component of velocity of fluid flow, which apparatus comprises first and second units spaced apart and each adapted to transmit and receive pressure wave pulses travelling over a path through the fluid in the direction in which velocity component is to be measured, variable frequency oscillator means, trigger means for causing a pressure wave pulse to be transmitted from the first unit to the second unit and, separately, from the second unit to the first unit, and control means for adjusting the variable frequency oscillator means to generate a first frequency dependent upon the time taken for a pressure wave pulse to travel from the first unit to the second unit and to generate a second frequency dependent upon the time taken for a pressure wave pulse to travel from the second unit to the first unit, a difference determining means for determining the difference between said first and second frequencies, and inhibitor means for inhibiting adjustment of the oscillation or pulse repetition frequency in the event that no pressure wave pulse is received within a predetermined period embracing its expected time of arrival.
-
29. Apparatus as claimed in claim 28, wherein the variable frequency oscillator means is controlled by the said control means to generate a number N1 of oscillations or pulses in a first time period being that taken for a pressure wave pulse to travel from the first unit to the second unit and a number N2 of oscillations or pulses in a second time period being that taken for a pressure wave pulse to travel from the second unit to the first unit, said control means comprising logic circuitry for comparing the times of occurrence of the N1th oscillation or pulse with the time of arrival of the pressure wave pulse at the second unit and for comparing the time of occurrence of the N2th oscillation or pulse and the time of arrival of the pressure wave pulse at the first unit, the said oscillation or pulse repetition frequency being adjusted to tend to bring the said times of occurrence of the N1th or N2th oscillation or pulse into coincidence with the time of aRrival of the respective pressure wave pulse, the said difference determining means indicating the difference in frequency between the oscillations or pulses generated in the first time period and the oscillations or pulses generated in the second time period.
Specification