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US 5,052,230 AGranted
Method and arrangement for flow rate measurement by means of ultrasonic waves
AssigneeFlowtec AG
InventorsMichael Lang, Michael Steinacher
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AssigneeFlowtec AG
InventorsMichael Lang, Michael Steinacher
Estimating the term…
For flow rate measurement by means of ultrasonic waves, on a measuring tube two ultrasonic transducers are arranged spaced apart from each other, one operating as transmitting transducer and the other as receiving transducer. For determining the flow rate the phase shift between the transmission signal and the reception signal is measured digitally in that the measuring time intervals corresponding to the phase shift the periods of a signal are counted with a counting frequency which is substantially greater than the frequency of the transmission signal. The start phase which the counting frequency signal has at the beginning of each counting operation with respect to the measuring time interval is varied from measuring time interval to measuring time interval in a measuring cycle including a plurality of successive measuring time intervals and the counts obtained in the course of the measuring cycle are evaluated to form a measured value with increased measurement resolution.
Method for flow rate measurement by means of ultrasonic waves which are propagated in a medium flowing through a measuring tube (10) between two ultrasonic transducers (12, 14) which are arranged spaced a defined distance apart from each other and of which the one operates as transmitting transducer converting an electrical transmission signal (U.sub.S) to an ultrasonic wave of the same frequency (f.sub.M) whilst the other operates as receiving transducer converting the incoming ultrasonic wave to an electrical reception signal (U.sub.E) of the same frequency, the phase shift between the transmission signal (U.sub.S) and the reception signal (U.sub.E) being measured to determine the flow rate, the method comprising the steps of generating a counting frequency signal (I.sub.C) with a counting frequency (f.sub.C) substantially greater than the measuring frequency (f.sub.M), counting the periods of the counting frequency signal (I.sub.C) in measuring time intervals (T.sub.I) corresponding to the phase shift between the transmission signal (U.sub.S) and the reception signal (U.sub.E), varying a start phase (.phi..sub.S) which the counting frequency signal (I.sub.C ) has at the beginning of each counting operation with respect to the measuring time interval (T.sub.I) from measuring time interval to measuring time interval in a measuring cycle (T.sub.R) including a plurality of consecutive measuring time intervals (T.sub.I), and evaluating the counts obtained in the course of the measuring cycle (T.sub.R) to form a measured value with increased measurement resolution.
Arrangement for flow rate measurement by means of ultrasonic waves comprising a measuring tube (10) traversed by a medium, two ultrasonic transducers (12, 14) arranged on the measuring tube (10) at a definite distance (L.sub.M) from each other, means for applying an electrical transmission signal (U.sub.S) with a measuring frequency (f.sub.M) to one of the two ultrasonic transducers which operates as transmitting transducer converting said electrical transmission signal (U.sub.S) to an ultrasonic wave of the measuring frequency which is propagated in said medium while the other ultrasonic transducer operates as receiving transducer converting the ultrasonic wave to an electrical reception signal (U.sub.E) of the measuring frequency, means for receiving the electrical reception signal (U.sub.E) with the measuring frequency emitted by the other ultrasonic transducer, a counting frequency generator generating a counting frequency signal (I.sub.C) with a counting frequency (f.sub.C) substantially greater than the measuring frequency (f.sub.M), a counter (30) counting the periods of the counting frequency signal (I.sub.C) in measuring time intervals (T.sub.I) which correspond to the phase shift between the transmission signal (U.sub.S) and the reception signal (U.sub.E), and an evaluating circuit (32) to which the count reached in each measuring time interval (T.sub.I) is transferred, characterized by means which vary the start phase (.phi..sub.S) which the counting frequency signal (I.sub.C) has at the beginning of each counting operation with respect to the measuring time interval (T.sub.I) from measuring time interval to measuring time interval in a measuring cycle (T.sub.R) including a plurality of consecutive measuring time intervals (T.sub.I).
Arrangement according to 23, characterized by a pulse generator (202) which for the determination of the number (m) of whole wavelengths of the ultrasonic wave in the measuring tube (10) applies a short single pulse (I.sub.D) to one of the two ultrasonic transducers (12, 14) so that the latter is stimulated to transmit a short wave train, a counter (222) which is set in operation on application of the single pulse (I.sub.D) for counting a counting signal (S.sub.R) with the transmission frequency (f.sub.M) or an integer multiple (2.multidot.f.sub.M) of the transmission frequency, and by a pulse-receiving circuit (210) which is connected to the other ultrasonic transducer and stops the counter (222) on arrival of the short wave train at the other ultrasonic transducer.
Dependencies are inferred from the claim text.