Apparatus and method for controlling an ultrasonic transducer

• US 5,900,690 A
• Filed: 06/26/1996
• Issued: 05/04/1999
• Est. Priority Date: 06/26/1996
• Status: Expired due to Term

• Current Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Original Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Inventors: Cohen, Bernard, Jameson, Lee Kirby, Gipson, Lamar Heath
• Primary Examiner(s): Dougherty, Thomas M.
• Application Number:
  US08/671,266
• Time in Patent Office: 1,042 Days
• Field of Search: 310/316
• US Class Current: 310/316.01
• CPC Class Codes: B06B 1/0246 with a feedback signal
• CPC Class Codes: B06B 2201/70 Specific application

Abstract

An apparatus and method for controlling an ultrasonic transducer preferably including a signal generator circuit, a signal sensing circuit, a modulator circuit, and a bias circuit. The signal generator circuit provides a pulsed drive signal to the ultrasonic transducer. The signal sensing circuit senses the voltage and current of the drive signal. The modulator circuit provides a frequency control signal and an energy control signal to the signal generator circuit corresponding to a detected phase difference between the sensed voltage and the sensed current of the drive signal. The frequency control signal and energy control signal operate 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.

Claims

1. An apparatus for controlling an ultrasonic transducer, comprising:

a signal generator for providing a pulsed drive signal to drive said ultrasonic transducer, said pulsed drive signal having a frequency level and an energy level;

a feedback means for providing a modulation control signal to said signal generator, the value of said modulation control signal corresponding to a phase difference between the voltage level of said used drive signal and the current level of said pulsed drive signal;

said signal generator being operative to adjust said frequency level of said pulsed drive signal in response to said value of said modulation control signal; and

said signal generator being further operative to adjust said energy level of said pulsed drive signal in response to said value of said modulation control signal without changing said frequency level of said pulsed drive signal, so as to substantially eliminate said phase difference, wherein said modulation control signal is further operative to provide a substantially real-time indication of the viscosity of a liquid when said liquid is in contact with said ultrasonic transducer.

2. An apparatus for controlling an ultrasonic transducer, comprising:

a signal generator for providing a pulsed drive signal to drive said ultrasonic transducer;

a signal sensing means for providing a voltage sense signal in response to the voltage level of said pulsed drive signal and for providing a current sense signal in response to the current level of said pulsed drive signal;

a modulator for providing a frequency control signal and an energy control signal to said signal generator, the value of said frequency control signal and the value of said energy control signal corresponding to a phase difference between said voltage sense signal and said current sense signal;

said signal generator being operative to adjust the frequency of said pulsed drive signal in response to the voltage level of said frequency control signal; and

said signal generator being operative to adjust the energy level of said pulsed drive signal in response to the voltage level of said energy control signal without changing the frequency of said drive signal, whereby said phase difference is substantially eliminated, wherein said frequency control signal is further operative to provide a substantially real-time indication of the viscosity of a liquid when said liquid is in contact with said ultrasonic transducer.

3. A method of controlling an ultrasonic transducer, comprising the steps of:

providing a pulsed drive signal to drive said ultrasonic transducer, said pulsed drive signal having a voltage level and a current level;

providing a modulation control signal, the value of said modulation control signal corresponding to a phase difference between said voltage level of said pulsed drive signal and said current level of said pulsed drive signal;

in response to a change in said value of said modulation control signal, changing said pulsed drive signal by adjusting the frequency of said pulsed drive signal; and

in response to said change in said value of said modulation control signal, changing said pulsed drive signal by adjusting the energy level of said pulsed drive signal without changing the frequency of said pulsed drive signal, so as to substantially eliminate said phase difference, wherein said modulation control signal is further operative to provide a substantially real-time indication of the viscosity of a liquid when said liquid is in contact with said ultrasonic transducer.