AN APPARATUS AND METHOD FOR CONTROLLING AN ULTRASONIC TRANSDUCER

摘要

An apparatus (108) and method for controlling an ultrasonic transducer (107a) preferably including a signal generator circuit (502), a signal sensing circuit (504), a modulator circuit (506) and a bias circuit (508). The signal generator circuit provides a pulsed drive signal to the ultrasonic transducer. The signal sensing circuit senses the voltage (510) and current (512) of the drive signal. The modulator circuit provides a frequency control signal (516) and an energy control signal (514) to the control signal generator circuit corresponding to a detected phase difference between the sensed voltage and the sensed current of the drive (503) signal. The frequency control signal and energy control signal operated to adjust the frequency and energy level, respectively, of the drive signal. Within the transducer, a movable element in contact with a liquid is preferably positioned corresponding to the level of a dc bias signal provided by the bias circuit. By adjusting the level of the dc bias signal, the flow rate of the liquid is adjusted. By applying the drive signal to the transducer, the viscosity of the liquid is adjusted which establishes a second flow rate of the liquid. When the frequency and energy level of the drive signal are changed, a third flow rate of the liquid is established.