Ultrasonic flowmeter systems

Claim 2

In a flowmeter, the combination of 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 transducer 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 transmitted downstream from said first transducer means to the second transducer means are recirculated to the first transducer means through said second feedback path, means for causing N pulses to be transmitted from both said first and second transducer means over a given time interval whereby each transmitted pulse will have a corresponding received pulse which is delayed with respect to its tranSmitted pulse, and circuit means coupled to said feedback paths for generating a signal proportional to the time delay between only the Nth received pulses in the respective feedback paths and for modifying said signal by an amount dependent upon the speed of sound in said fluid at rest, said modified signal providing an indication of fluid flow.

Claim 3

The combination of claim 1 wherein said modified signal is proportional to the quantity c2N Delta t where N Delta t is the time difference between the Nth received pulses in the respective feedback paths and c is the speed of sound in said fluid at rest.

Claim 4

The combination of claim 2 including means for determining c2 from the transit time of pulses between said transducer means.

Claim 5

The combination of claim 3 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 waveform at a time corresponding to a specific received pulse to generate a signal which modifies the determined rate of flow.

Claim 6

In a flowmeter, the combination of 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 transducer 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 transmitted downstream from said first transducer means to the second transducer means are recirculated to the first transducer means through said second feedback path, means for causing the same number N of pulses to be transmitted from both said first and second transducer means over a time interval whereby each transmitted pulse will have a corresponding received pulse which is delayed with respect to its transmitted pulse, and electrical circuitry coupled to said feedback paths for generating a signal dependent upon the speed of sound in said fluid at rest and proportional to Delta t + 2 Delta t + 3 Delta t + . . . + N Delta t where Delta t is the time difference between the first received pulses of said same number in the respective sing-around loops.

Claim 7

In a flowmeter, the combination of 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 transducer 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 transmitted downstream from said first transducer means to the second transducer means are recirculated to the first transducer means through said second feedback path, means for causing the same number N of pulses to be transmitted from both said first and second transducer means over a time interval whereby each transmitted pulse will have a corresponding received pulse which is delayed with respect to its transmitted pulse, and electrical circuitry coupled to said feedback paths for generating a signal dependent upon the speed of sound in said fluid at rest and proportional to Delta t + 2 Delta t + 3 Delta t + . . . + N Delta t where Delta t is the time difference between the first received pulses of said same number in the respective sing-around loops.

Claim 8

In a flowmeter, the combination of at least one pair of oppositely disposed ultrasonic transducer means located in acoustic contact with a fluid stream, a first feedbath 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 downstream from said first transducer means to the second transducer means are recirculated to the first transducer means through said second feedback path, means for causing the same number N of pulses to be transmitted from both said first and second transducer means over a time interval whereby each transmitted pulse will have a corresponding received pulse which is delayed with respect to its transmitted pulse, the initial transmitted pulses in the respective feedback paths being delayed with respect to each other by a time delay Tau , and electrical circuitry coupled to said feedback paths for generating a signal dependent upon the speed of sound in said fluid at rest and proportional to Tau + ( Delta t + Tau ) + (2 Delta t + Tau ) + (3 Delta t + Tau ) . . . + (N Delta t + Tau ), where OT is the time difference between the first received pulses of said same number in the respective ring around loops.

Claim 9

In a flowmeter, the combination of at least one pair of oppositely disposed ultrasonic transducer means located in acoustic contact with a fluid stream, a first feedbath 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 downstream from said first transducer means to the second transducer means are recirculated to the first transducer means through said second feedback path, means for causing the same number N of pulses to be transmitted from both said first and second transducer means over a time interval whereby each transmitted pulse will have a corresponding received pulse which is delayed with respect to its transmitted pulse, the initial transmitted pulses in the respective feedback paths being delayed with respect to each other by a time delay Tau , and electrical circuitry coupled to said feedback paths for generating a signal dependent upon the speed of sound in said fluid at rest and proportional to Tau + ( Delta t + Tau ) + (2 Delta t + Tau ) + (3 Delta t + Tau ) . . . + (N Delta t + Tau ), where OT is the time difference between the first received pulses of said same number in the respective ring around loops.