Abstract: In a method for measuring flow by means of an ultra sonic flow meter, an ultra sonic signal is transmitted in an upstream and a downstream direction. This is measured upon receipt of an ultra sonic signal and the measurement stopped at a stopping point. A first series of transmissions is made, and the starting time of each transmission is incremented or decremented until a time difference between the upstream and downstream signal is inside a reference band. Flow is then calculated in accordance with the time measurements.

Abstract: A transmitting and receiving circuit for an ultrasonic flowmeter. In such circuits, an ultrasonic transducer is typically used as both transmitter and receiver. This is obtained by using switching means, for example in the form of CMOS switches. However, problems arise with ringings of a transducer when having acted as a transmitter. This unwanted ringing makes the crystal of the transducer act as an additional signal generator, and the signal is coupled via parasitic capacitances in a switching means to the receiving ultrasonic transducer. This problem is solved by connecting one pole of a short circuit switch (S3, S4) to the ultrasonic transducer (TR1, TR2) or to the switching means (S1, S2) and the other pole of the short circuit switch to ground. Keeping the short circuit switch closed when the switching means is open, and open when the switching means is closed, creates a decoupling path for the unwanted signal, thereby improving the accuracy of the transmitting and receiving circuit.

Abstract: A transmitting and receiving circuit for an ultrasonic flowmeter. In such circuits, an ultrasonic transducer is typically used as both transmitter and receiver. This is obtained by using switching means, for example in the form of CMOS switches. However, problems arise with ringings of a transducer when having acted as a transmitter. This unwanted ringing makes the crystal of the transducer act as an additional signal generator, and the signal is coupled via parasitic capacitances in a switching means to the receiving ultrasonic transducer. This problem is solved by connecting one pole of a short circuit switch (S3, S4) to the ultrasonic transducer (TR1, TR2) or to the switching means (S1, S2) and the other pole of the short circuit switch to ground. Keeping the short circuit switch closed when the switching means is open, and open when the switching means is closed, creates a decoupling path for the unwanted signal, thereby improving the accuracy of the transmitting and receiving circuit.

Abstract: In a method for measuring flow by means of an ultra sonic flow meter, an ultra sonic signal is transmitted in an upstream and a downstream direction. This is measured upon receipt of an ultra sonic signal and the measurement stopped at a stopping point. A first series of transmissions is made, and the starting time of each transmission is incremented or decremented until a time difference between the upstream and downstream signal is inside a reference band. Flow is then calculated in accordance with the time measurements.

Abstract: Transmitting and receiving circuit for an ultrasonic flowmeter, comprising at least two ultrasonic transducers arranged for the transmission and receipt of ultrasonic signals in opposite directions across a measuring distance, a signal source for controlled production of electrical signals for transmission to the ultrasonic transducers and detection means for deriving transmission time measurements, used to calculate the flow, measuring of which is desired. The transmitting and receiving circuit includes an amplifier with a first inverting input terminal for connection to an ultrasonic transducer, a second non-inverting input terminal for connection to the signal source, an output terminal for connection with the detection means, and a feedback connection between the output terminal and the first input terminal.