Ultrasonic flow meter with subsampling of ultrasonic transducer signals
An ultrasonic flow meter is disclosed, including a switching unit for switching electrical transmission signals between a signal generator and at least two ultrasonic transducers and for switching electrical reception signal between the transducers and a receiver circuit, wherein the switching unit is coupled to an output terminal of an operational amplifier of the signal generator and to an inverting input terminal of an operational amplifier of the receiver circuit. Furthermore, a method for characterizing an ultrasonic transducer is disclosed, including the step of determining directly from one or more supply current signals for an active component of a signal generator one or more quantities useful for characterizing the transducer. Furthermore, a method for determining the time delay of an ultrasonic signal in a flow path of an ultrasonic flow meter is disclosed, including the step of comparing physically transmitted, delayed and received signals with simulated non-delayed signals.
1. An ultrasonic flow meter comprising:
a flow path for fluid flow;
at least two ultrasonic transducers acoustically coupled to the flow path, a first transducer of the at least two ultrasonic transducers being arranged upstream of a second transducer of the at least two ultrasonic transducers along the flow path;
a signal generator for generating electrical transmission signals to the at least two ultrasonic transducers, the signal generator comprising a first negative feedback coupled operational amplifier;
a receiver circuit for receiving electrical reception signals from the at least two ultrasonic transducers, the receiver circuit comprising a second negative feedback coupled operational amplifier;
a switching unit for switching the electrical transmission signals between the signal generator and the at least two ultrasonic transducers and for switching the electrical reception signal between the at least two ultrasonic transducers and the receiver circuit; and
a signal processing unit for providing an output indicative of a flow rate of the fluid flow in the flow path based on the electrical reception signals;
wherein the switching unit is coupled to an output terminal of the first negative feedback coupled operational amplifier of the signal generator and the switching unit is coupled to an inverting input terminal of the second negative feedback coupled operational amplifier of the receiver circuit, and
wherein an output impedance of the signal generator and an input impedance of the receiver circuit are negligible, at less than 1%, compared to the impedance of the at least two ultrasonic transducers.
2. The flow meter of claim 1 , wherein the signal generator and the receiver circuit share at least one active component.
3. The flow meter of claim 1 , wherein all active components of the signal generator are completely separate from all active components of the receiver circuit.
4. The flow meter of claim 1 , wherein one or more of the first negative feedback coupled operational amplifier and the second negative feedback coupled operational amplifier are current feedback operational amplifiers.
5. The flow meter of claim 1 , wherein one or more of the first negative feedback coupled operational amplifier and the second negative feedback coupled operational amplifier are operated at an input common mode voltage, an AC component of which is substantially zero.
6. The flow meter of claim 1 , wherein the at least two ultrasonic transducers are arranged to be able to transmit an ultrasound signal simultaneously.
7. The flow meter of claim 1 , wherein the at least two ultrasonic transducers are two ultrasonic transducers.
8. The flow meter of claim 1 , wherein the output impedance of the signal generator and the input impedance of the receiver circuit are less than 10 Ohms.
9. The flow meter of claim 1 , wherein the output impedance of the signal generator and the input impedance of the receiver circuit are less than 1 Ohm.
10. The flow meter of claim 1 , wherein the output impedance of the signal generator and the input impedance of the receiver circuit are less than 0.1 Ohm.