主权项 |
1. A circuit, comprising:
an ultrasonic transducer having a driver side, a bias voltage side, and a piezoelectric flexure mechanically fixed at one end to a location at a wall of a container in mechanical contact with a membrane; a higher voltage source electrically connected to the bias voltage side of the ultrasonic transducer through a first resistor; a lower voltage source electrically connected to the driver side of the ultrasonic transducer through a second resistor; and a switch having a source, a gate and a drain, the source electrically connected to ground, the gate electrically connected to a control signal source, the drain electrically connected to the lower voltage source through the first resistor and electrically connected to the driver side of the ultrasonic transducer. |