| 主权项 |
1. An ultrasonic flow meter arranged to measure a flow rate of a fluid, wherein the ultrasonic flow meter comprises:
at least two ultrasonic transducers arranged for transmission and receipt of ultrasonic signals in opposite directions across a measuring distance, wherein the at least two ultrasonic transducers comprise at least a first transducer positioned at one end of the measuring distance and at least a second ultrasonic transducer positioned at the other end of the measuring distance; a transducer switch electrically connected to the at least two ultrasonic transducers; a generator circuit for controlled generation of electrical signals for transmission to the at least two ultrasonic transducers, wherein the generator circuit comprises or is connected to a signal source; a receiver circuit for receiving electrical signals from the at least two ultrasonic transducers, the receiver circuit being separate from the generator circuit, wherein the receiver circuit comprises a receiver output for connection to a detector;wherein the transducer switch is arranged for controlled functional connection of:
the first ultrasonic transducer to either the generator circuit or the receiver circuit, and the second ultrasonic transducer to either the generator circuit or the receiver circuit;so that the first ultrasonic transducer is electrically connected to the generator circuit and the second ultrasonic transducer is electrically connected to the receiver circuit, or vice versa, wherein an output impedance of the generator circuit as seen from the at least two ultrasonic transducers is substantially zero, and wherein an input impedance of the receiver circuit as seen from the at least two ultrasonic transducers is substantially zero,wherein the generator circuit comprises an operational amplifier with a first input connected to the signal source, a second input and an output connected to the second input via a feedback connection, and wherein the second input is further connected to the transducer switch so that the second input is operationally connected to the at least two transducers via the switch, and
wherein the receiver circuit comprises an operational amplifier with a third input connected to ground or to a reference potential, a fourth input and a second output connected to the fourth input via a feedback connection, and wherein the fourth input is further connected to the transducer switch so that the fourth input is operationally connected to the at least two transducers via the switch. |
