Improvements in or relating to ultrasonic flowmeter systems

Claim 1

25,5 7 5 rn THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A flowmeter, including at least one pair of oppositely disposed ultrasonic transducer means located in acoustic contact with a fluid stream, a first feedback path coupling the output of a first of said transducer means to the input of a second of the transducer means such that signals transmitted upstream from said second transducer means to said first transducer means are recirculated to the second trans- ducer means through said first feedback path, a second feedback path coupling the output of said second transducer means to the input of said first transducer means such that signals trans- mitted downstream from said first transducer means to the second transducer means are recirculated to the first transducer mea ns through said second feedback path, means being provided for causing the same number of pulses to be transmitted from both said first and second transducer means over a predetermined time interval whereby each transmitted pulse will have a corres- ponding received pulse which is delayed with respect to its transmitted pulse, and means being provided coupled to said feedback paths for determining the rate of flow of said fluid stream from a consideration of an expanded time difference between corresponding received pulses in the respective feed- back paths over said number of pulse transmissions which occur during said predetermined time interval. 2. A flowmeter according to claim 1 wherein said first transducer means comprises both a receiving transducer and a sending transducer, arid wherein said second transducer means also comprises both a receiving transducer and a sending transducer. 447 511- 25,575 nl 3. A flowmeter according to claim 1 wherein said first transducer means comprises a single transducer which both receives and transmits pulses, and said second transducer means also comprises a single transducer which both receives and transmits pulses. 4. A flowmeter according to claim 1, 2 or 3 includ- ing means in each of said feedback paths for generating transmitted pulses, and means for enabling the transmitting means in one of said feedback paths to generate a first trans- mitted pulse and for enabling the transmitting means in the other feedback path to generate a first transmitted pulse after a predetermined time delay following transmission of the first pulse in said one feedback path. A flowmeter according to claim 4 wherein each of said feedback paths includes an amplifier for received pulses, an astable multivibrator synchronized by the output of said amplifier, and a blocking oscillator triggered by the -output of said multivibrator. 6. A flowmeter according to any preceding claim wherein there are N pulses transmitted upstream and downstream, and means are provided for determining the time delay between the Nth received pulses in the respective feedback paths to determine the rate of flow of said fluid. 7. A flowmeter according to claim 6 wherein the rate of flow of said fluid is determined from the quantity c 2 N At where N At is the time difference between the Nth received pulses in the respective feedback paths and c is the speed 29 4 4 751f 5 7 5 ni1 of 3ow-±d in said fluid at rest. 8. A flowrnetcr according to claim 7 wherein c2 is determined from the transit time of pulses between said trans- ducer means. 9. A flowmeter according to any of claims 1 to wherein there are N pulses transmitted upstream and downstream wherein means is providedfor producing electrical signals each proportional to the time dela y between corresponding received pulses moving upstream and downstream from each pair of transmitted pulses, and means is provided for summing said electrical signals to determine said rate of fluid flow. A flowmeter according to any of claims 1 to wherein pulses are transmitted upstream and downstream for a f'ixed period of time during each repetition cycle regardless of the number of pulses transmitted dviring that period. 11. A flowmeter according to any preceding claim including means for generating a waveform. and for' producing an output which closely approximates the inverse of the square of time following a specific transmitted pulse, and means for sampling the instantaneous value of said waveformat a time corresponding to a specific received pulse to generate a signal which modifies the determined rate of flow. 12. A flowmeter according to claim 6 wherein the Nth pulse In said one feedback path is delayed by a time interval eq'nual to said predeter'mined time delay to provide pulses separated in time by N At which time interval is measured to indicate f luid velocity.4751 25,5 7 5 13. A flowmeter, according to any preceding claim wherein said ultrasonic transducer means operates as a pair of sing-around loops for causing the same predetermined number of pulses N to te transmitted upstream and downstream in the flow cf fluid, and wherein means is provided coupled to said sing-around loops for determining the rate of flow of said fluid from the quantity 2N A t where N At is the time difference between the Nth received pulses in the respective sing-around loops and c is the speed of scund in said fluid at rest. 14. A flowmeter according to any of claims 1 to 12 wherein said ultrasonic transducer means operates as a pair of sxig-around loops for causing the same predetermined number of pulses N to be transmitted ucstream and downstream in a flow of fluid, and wherein means is provided coupled to said sing-around loops for determining the rate of flow of said fluid from a consideration of: At 2 At 3At NAt where A t is the time difference between the first received pulses of said predetermined number in the respective sir& around loops. A flowmeter according to claim 14 wherein the initial transmitted pulses in the respective sing-around loops are delayed with respect to each other by a time delay/ and said rate of fluid flow is determined from a consideration of: (At (2At (3At +(Nit 5 1 16. 25, 5 7 5 /71 A flow-meter, according to any of claims 1 to 12 wherein said ultrasonic transducer means operates as a pair of sing-around loops for causing pulses to be transmitted upstream and downstream in a flow of fluid over a predetermined fixed time interval and in a manner such that for each pulse transmitted upstream a corresponding pulse is transmitted downstream before the next upstream pulse is transmitted, and wherein means is provided for determining the rate of flow of said fluid from a consideration of the summation of the time differences between received pulses due to corresponding t==ietted pulses in the respective sing-around loops over said predetermined fixed time interval. 17. A flowmeter substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings. DATED This 15th day of FEBRUARY, 1971. WESTINGHOUSE ELECTRICCORPORATION By its Patent Attorneys: CLEMENT HACK CO. Fellows Institute of Patent Attorneys of Australia. 447511 32" 575 /71 K-- C+V A TRANSMIT Re L FIdI. A RECEIVE B TRANSMIT K Ralw A R B RECEIVE at 8 Yvl. FIG.3. 0 IA tB TIME- FIG.2. Ao Al A5' AN A TRANSMIT T 31 4t 5 1IA 2A A A A A RECEIVE__ I I 80 7 Ba I B3 84 B5'BN FIG. BTRANSMIT I I B RECEIVE 0 2tB I TIME- 3 tB I 4 NO 5 tB I A TRANSMIT A I T A A2 A3 A4 A RECEIVE -I lij~R B TRANSMIT BT I I FIG.58. 81 B2 B3 B4 A,' B RECEIVE I BR .t X2 i I TIME- 5 7 5 /71 F! I.- ~-0 447 5 11 25,575 ni- r- I 5 7 5 /71 0 Al A2 A3 A4 A I I I I I I B 4 B I10 o I I2 83 I r I at n 2At 3At 4At TIME FI G. 9 A. ATRANSMIT 2 I 3 I 41 I AT tA tA tA A 5tA BTRANSMIT I I t I I IT t tB+T 3tB+T 4tBFr 5tBF GB n 68 2 r UI L ,PIP-,Pr' OUTPUT A 2 W2+T L 3W+T 41i+C: 5C1* CRCUT7OTl n n E2 n n n n E v t FIG. 9 B. 5 7 5 171 0 o 0 m w 0 -1 OIL 0 0< I-M -i ki a0 i-JZ c0 447 511