Abstract:
An ultrasonic driver determines an optimal operating frequency for an ultrasonic transducer, and drives the transducer at its optimal frequency. A microcontroller controlling a MOSFET driver selectively alters the operating frequency of the transducer until a maximum operating current is detected by a transducer performance detector. The transducer performance detector provides an acknowledgment signal to the microcontroller upon detecting the maximum operating current, causing the microcontroller to lock the operating frequency at the current, optimal value.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    The present application is related to Ser. No. ______, entitled “Microcontroller Unit,” filed concurrently with the present invention on Jun. 4, 2002 by inventors common to the present application, and which is hereby incorporated by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of Invention  
           [0003]    The present invention relates generally to the field of transducers. More specifically, the present invention relates to ultrasonic scaler transducers.  
           [0004]    2. Discussion of Prior Art  
           [0005]    Piezo-electric devices are well known in the prior art. An important aspect of a piezo-electric device is that it operates at an optimum frequency at which its impedance is lowered near a minimum value. This optimal frequency provides for the best performance of a piezo-electric device.  
           [0006]    One use of piezo-electric devices is in the field of dentistry, where such a device may be used in a scaler. For best performance, the device needs to be driven at an optimal frequency. It should, however, be noted that a common problem associated with prior art scalers is that the operating frequency is based upon various factors including: the particular mass of the scaler tip, the shape, and the water load in a water spray at the end. These factors (and many others) cause variation in the optimum operating frequency for the device.  
           [0007]    Prior art devices are simply provided with a preset frequency that is considered optimum, and factors such as change of mass and other environmental factors are not taken into account. Thus, due to these factors, a device may operate at a frequency other than its optimal frequency for a particular configuration. Therefore, to overcome the limitations of the prior art, there is a need to be able to dynamically monitor and determine the optimal frequency associated with a scaler, and then to set the frequency accordingly.  
           [0008]    The following references describe prior art in the field of piezo-electric devices, in general.  
           [0009]    The U.S. patent to Isono (U.S. Pat. No. 3,992,679), assigned to Sony Corporation, provides for a locked oscillator having a control signal derived from output and delayed output signals. Disclosed within the patent is a stabilized frequency oscillating circuit having a voltage-controlled variable frequency oscillator with a closed control loop to lock the oscillator to a predetermined mined frequency. It should be noted that the oscillator described in this patent is used to compare phase.  
           [0010]    The U.S. patent to Balamuth et al. (U.S. Pat. No. 4,012,647), assigned to Ultrasonic Systems, Inc., provides for ultrasonic motors and converters. Disclosed within the patent is a transducer means having a pair of piezoelectric crystals attached to a removable tip. A third crystal forms a part of a sensing means for detecting a frequency of the ultrasonic motor. Additionally, the feedback signal is utilized by the converter to adjust itself. It should be noted that this patent provides for a power oscillator with feedback.  
           [0011]    The U.S. patent to Hetzel (U.S. Pat. No. 5,059,122), assigned to Bien-Air S.A., provides for a dental scaler. Disclosed within the patent is a dental scaler having a vibrating piezoelectric transducer and an Amplifier connected to the transducer. The transducer has a series of piezoelectric chips for vibrating the head of a scaler. The series of piezoelectric chips are coupled with electrodes in such a manner to define an input, an output, and two feeder terminals receiving a low direct voltage from an external source of voltage. The input and output of the amplifier are connected to the input and output of the transducer respectively for forming an oscillator. The transducer is connected to the scaler to form a resonator and the amplifier forms a maintenance circuit. The transducer vibrates at its resonant frequency.  
           [0012]    The U.S. patent to Sharp (U.S. Pat. No. 5,451,161), assigned to Parkell Products, Inc., provides for an oscillating circuit for ultrasonic dental scaler. Disclosed within the patent is an oscillating circuit, which is automatically tuned to vibrate a scaler insert at its resonant frequency in response to an impedance of an energizing coil.  
           [0013]    The U.S. patent to Sharp (U.S. Pat. No. 5,730,394), assigned to Parkell Products, Inc., provides for an ultrasonic dental scaler selectively tunable either manually or automatically. Disclosed is an ultrasonic dental scaler, which has a selectively tunable oscillator circuit coupled to an energizing coil L HND . It generates a control signal having an oscillation frequency associated with the energizing coil L HND . An oscillator circuit U 1  includes a switch S 3  which is operatively coupled to automatic and manual timers in order to alter the oscillation frequency. The oscillator circuit U 1  is a phase-locked loop with a phase comparator. It should be noted that the U.S. Pat. No. 6,190,167 B1 teaches along similar lines.  
           [0014]    The U.S. patent to Sale et al. (U.S. Pat. No. 5,927,977) assigned to Professional Dental Technologies, Inc., provides for a dental scaler. Disclosed is a dental scaling system having an ultrasonic transducer to vibrate the scaling tip. Handpiece control electronics control the electrical energy provided to the heater and the ultrasonic transducer.  
           [0015]    The U.S. patent to Boukhny et al. (U.S. Pat. No. 5,938,677), assigned to Alcon Laboratories, Inc., discloses a control system for a phacoemulsification bandpiece. The control system includes a digital signal processor (DSP) for measuring responses of a phacoemulsification handpiece to a varying drive signal from voltage source VCO, and for comparing these responses to determine the probable value of the actual series resonance f s  (the peak of admittance curve). The DSP controls the current I of the drive signals constant with a PID control logic. The patent describes a unit that scans a range, measures the admittance (ratio of current to drive voltage), stores the parameters, analyzes the amplitudes, and calculates an average.  
           [0016]    The U.S. patent to Alexandre et al. (U.S. Pat. No. 5,739,724), assigned to Sollac and Ascometal S.A., provides for control of an oscillator for driving power ultrasonic actuators. Disclosed within the patent is a power generator for providing controlled electric power to the ultrasonic actuators. A voltage current measurement circuit measures the voltage and current supplied by the power generator. The circuit supplies a computer with signals representative of the strength of the current and of the phase between the voltage and the current. The computer controls an interface which drives the power generator. The operator car, set the frequency range, type of search (resonance or anti-resonance), and voltage used for the search.  
           [0017]    The U.S. patent to Noma et al. (U.S. Pat. No. 6,144,139), assigned to Murata Manufacturing Co., Ltd., provides for a piezoelectric transformer inverter. Disclosed within the patent is a piezoelectric transformer converter that has a step-up ratio as a function of a driving frequency. The load current is controlled to be constant with different step-up ratios and frequencies.  
           [0018]    The U.S. patent to Sakurai (U.S. Pat. No. 6,019,775), assigned to Olympus Optical Co., Ltd., provides for an ultrasonic operation apparatus having a common apparatus body usable for different handpieces. Disclosed within the patent is a handpiece having an ultrasonic oscillation element, a phase locked loop (PLL) circuit and a current detection section. The PLL circuit tracks the resonant frequency f3 of element and generates a correspondent signal. A current phase signal detected at the current detection section is sent to the PLL circuit. The phase at the ultrasonic oscillation element is set to zero degrees.  
           [0019]    The German patent to Wieser (DE 2,929,646) assigned to Medtronic GmbH, provides for an oscillator for dental treatment that has a multivibrator supplying a signal via an RC element to a switching transistor with the transducer winding connected at the collector circuit of transistor. The collector circuit is connected via a diode to an integration stage. The oscillator generates pulses whose frequency can be corrected by a closed loop control voltage.  
           [0020]    The German patent to Sturm (DE 2,011,299) provides for an ultrasonic generator which includes an amplifier (coupled in an oscillator configuration) for initiating, via an exciting impedance, ultrasonic vibrations in an electro-acoustic element such as that associated with a dental instrument.  
           [0021]    The German patent to Teichmann (DE 3,136,028) provides for a magnetostrictive ultrasonic oscillator circuit. Disclosed within the patent is a flip-flop circuit used as a variable-frequency ultrasonic generator for a dental hand piece. A hand piece coil L is fed by the variable-frequency ultrasonic generator, which can be tuned to resonance frequency. An RC feed back (R 7 - 9 , C 2 ) with two different time constants, dependent on the inductive load current of the coil L, is used for frequency determination of the ultrasonic generator.  
           [0022]    The German patent to Weiser (DE 2,459,841) provides electrical drive and control for ultrasonic dental equipment that has an oscillator supplying an impulse signal for a transformer. Disclosed within the patent is a magnetostrictive transformer (of a tartar deposit removing instrument), which is provided with impulse signals from the oscillator. The oscillator (a multivibrator) has its frequency stabilized by an open-loop/closed loop control voltage. The open-loop/closed loop control signal derived from the current through the transducer is fed to the oscillator for fine-tuning the frequency.  
           [0023]    Whatever the precise merits, features and advantages of the above cited references, none of them achieves or fulfills the purposes of the present invention.  
         SUMMARY OF THE INVENTION  
         [0024]    The present invention provides for a dental scaler device that comprises a microcontroller, a driver and a transducer performance detector. The transducer performance detector monitors and detects the best performance (i e., optimal frequency) of a transducer of the scaler with the help of the microcontroller. The microcontroller provides a drive frequency to the driver, and continually adjusts the frequency until an optimal performance is detected by the transducer performance detector. When an optimal performance is detected, the frequency of optimal performance is identified and locked for a period of operation.  
           [0025]    The microcontroller includes a digital frequency generator providing a multiplicity of frequencies. Each time the frequency is adjusted, the transducer is driven at the selected frequency and the driver current is measured by the transducer performance detector. This process continues as the microcontroller continues, for example, stepping the frequency upward or downward in increments, with the driver current measured each time. When the driver current reaches a peak, a signal is fed back to the microcontroller instructing it to lock in place the currently selected frequency (i.e., an optimal frequency) corresponding to the peak current. The microcontroller then drives the transducer at the locked optimal frequency, thereby allowing for operation of the transducer at its best performance setting. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0026]    A more complete understanding of the invention may be obtained by reading the following description of specific illustrative embodiments of the invention in conjunction with the appended drawing in which:  
         [0027]    [0027]FIG. 1 illustrates the concept of piezo transducer resonance;  
         [0028]    [0028]FIG. 2 illustrates a block diagram representative of a preferred embodiment of the present invention;  
         [0029]    [0029]FIG. 3 illustrates the “chase effect” as implemented in the peak comparator of FIG. 2;  
         [0030]    FIGS.  4 A- 4 G show timing diagrams associated with various nodes in FIG. 2;  
         [0031]    [0031]FIG. 5 illustrates a detailed system diagram of the microcontroller in FIG. 2;  
         [0032]    [0032]FIG. 6 illustrates a prior art piezo driver circuit; and  
         [0033]    [0033]FIG. 7 illustrates a flowchart describing the methodology associated with the preferred embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    While this invention is illustrated and described in a preferred embodiment, the dental scaler device may be produced in many different configurations, forms and materials. There is depicted in the drawing, and will herein be described in detail, a preferred embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and the associated functional specifications for its construction and is not intended to limit the invention to the embodiment illustrated. Those skilled in the art will envision many other possible variations within the scope of the present invention.  
         [0035]    In the preferred embodiment, the transducer is a piezo-electric transducer, although other equivalents such as a magnetostrictive transducer can be used without departing from the scope of the present invention.  
         [0036]    The present invention provides for a system and a method for identifying an optimal frequency associated with a transducer, and driving the transducer at the optimal frequency. In the preferred embodiment, the transducer is an ultrasonic piezo-electric scaler transducer for use in dental applications. It should be noted that the specific implementation of the present invention as a dental scaler is for illustrative purposes only, and should not be used to restrict the scope of the present invention.  
         [0037]    As illustrated in FIG. 1, the best performance with regard to the piezo-electric scaler is obtained at its transducer&#39;s series resonance Fo. At this series resonance, the transducer&#39;s impedance drops to its lowest possible value. Concurrently, at the lowest impedance value, the driver current reaches its highest point.  
         [0038]    [0038]FIG. 2 illustrates a block diagram of the preferred embodiment of the system of the present invention. FIG. 2 shows that the piezo element  5 ( a ) is driven by transformer T 1 , which is in turn driven by MOSFET driver  4  (comprising MOSFETs Q 1  and Q 2 ), and by the regulated power supply  1 . A sensing resistor R 1  is connected in series with the MOSFET driver  4 . A voltage developed across R 1 , is correlated to a current flow in the driver  4  (driver), which is further correlated with a current flow through piezo element PE. It should be noted that, as mentioned earlier, the piezo transducer  5 ( a ) is used merely to illustrate the preferred embodiment, and one skilled in the art can easily extend it to include other equivalent transducers such as a magnetostrictive transducer  5 ( b ), also shown in FIG. 2.  
         [0039]    The system of FIG. 2 is activated by pressing down foot switch S 1 , which in turn enables microcontroller  3  to provide signals  12 ,  13  at an incremented scanning frequency to driver  4 . The scanning frequency is produced by microcontroller  3 , regulated by system oscillator  2 . When the best performance of the piezo transducer  5 ( a ) is detected by transducer performance detector  6 , an output acknowledge signal  19  causes microcontroller  3  to lock the chosen frequency.  
         [0040]    The best performance of piezo element PE is detected by sensing a voltage developed across resistor R 1 . This voltage signal  16  is filtered by RC circuit  7  (R 2  and C 1 ), whose output at node  17  is fed into a peak comparator  8 . The peak comparator  8  directly receives the output signal at a negative input  8   a , as well as a delayed signal at node  18  via R 3  and C 2  fed directly into a positive input  8   b . An output  8   c  of this comparator directs acknowledge signal  19  to the microcontroller  3  to stop scanning and lock a current frequency when a maximum current I driver  has beet reached.  
         [0041]    The peak comparator  8  employs a “chase effect” which tracks the waveform developed by transducer  5   a  as it is correlated to the voltage across resistor R 1 . While microcontroller  3  operates in the scanning mode, the signal at the node  18  always trails the signal at node  17 . When the trailing signal at node  18  reaches the peak of its comparison, the signal at node  17  has already lessoned in voltage, and the voltage at node  18  becomes greater than the voltage at node  17 . Comparator  8  recognizes this event as a trigger to stop scanning, and outputs acknowledge signal  19  to microcontroller  3  in response.  
         [0042]    [0042]FIG. 3 illustrates the chase effect during frequency scanning as implemented in the peak comparator  8 . Voltages at nodes  17  and  18  are compared by peak comparator  8  of FIG. 2. The voltage at node  17  is greater than that of node  18 , until the peak F=Fo is reached as shown in the inset of FIG. 3. The inset illustrates the peak comparator trigger point after which the signal at node  18  is greater than that of node  17 . At this position, peak comparator  8  effectively identifies the frequency corresponding to the peak by signaling microcontroller  3  of FIG. 2 via acknowledge signal  19  to lock onto the current frequency as the optimal frequency.  
         [0043]    FIGS.  4 A- 4 G provide timing diagrams at various nodes ( 11 ,  12 ,  13 ,  16 ,  17 ,  18  and  19 ) introduced in FIG. 2. In FIG. 4A, node  11  becomes active with operation of foot switch S 1  of FIG. 2 by exhibiting a logical “0” output. As shown in FIGS. 4B and 4C, microcontroller  3  responds by outputting driver input signals at nodes  12 ,  13  to MOSFET driver  4  of FIG. 2. In a preferred embodiment of the present invention, as illustrated in insets to FIGS. 4B and 4C, the input signal at node  13  is arranged to trail the input signal at node  12  by approximately 200 nanoseconds. This delay helps to eliminate undesirable current switching noise from being supplied by MOSFET driver  4  of FIG. 2 to piezo element  5 ( a ). Without this delay, switching noise might otherwise be elevated by simultaneously operating more than one of driver transistors Q 1 , Q 2  of driver  4  in an “On” state.  
         [0044]    [0044]FIG. 4D illustrates voltage signal  16  across resistor R 1  of FIG. 2, which as depicted in FIG. 4D incrementally increases in frequency during scanning frequency period  30  until being locked at optimum frequency during locked frequency period  40 . FIGS. 4E, 4F respectively illustrate voltages at nodes  17  and  18  of FIG. 2 as a function of time. At a peak comparator trigger point between periods  30  and  40 , the voltages on curves  4 E,  4 F that are labeled as “Next event” illustrate the chase effect depicted in FIG. 3. Specifically, and as shown in the inset to FIG. 3, the “Next Event” voltage at node  17  of FIG. 4E is diminished from the “Next Event” voltage at node  18  of FIG. 4I. This condition triggers comparator  8  of FIG. 2 to generate acknowledge signal  19  (further described with respect to FIG. 4G). Discharging regions on the timing curves  4 E,  4 F for nodes  17 ,  18  are respectively associated with and influenced by capacitors C 1  and C 2  of FIG. 2, which allow the affected voltages at nodes  17 ,  18  to dissipate when I driver  terminates at the conclusion of period  40 .  
         [0045]    It can be seen that after the peak comparator trigger point, the operating frequency at node  16  is steady. As shown in FIG. 4G and FIG. 2, peak comparator  8  recognizes at the peak comparator trigger point that a maximum performance level has been reached, and provides acknowledge signal  19  in order to lock microcontroller  3  and driver  4  at an optimal operating frequency equal to the currently selected frequency. Operation continues at this frequency during locked frequency period  40 .  
         [0046]    A more detailed description of the operations of microcontroller  3  with reference to FIGS. 2, 5 is next presented. As shown in FIG. 2, the function of the microcontroller  3 , when the foot switch S 1  is activated, is to provide an incrementing frequency (scan frequency) to the piezo transducer  5 ( a ) (or manetostrictive transducer  5 ( b )), via MOSFET driver  4 . Upon detection of an optimal frequency (by transducer performance detector  6 ), acknowledge signal  19  instructs the microcontroller to stop incrementing, and to output only the currently selected frequency to the scaler transducer.  
         [0047]    Most ultrasonic transducers vibrate between 22 Khz and 50 Khz. If a best performance is not detected during the scanning process, microcontroller  3  is capable of indicating, via a signal supplied to node  21  of FIG. 2 (for example to illuminate an LED or other display attached to output  21 ), that the transducer is not responding. This signal may indicate to an operator, for example, that the transducer is defective. These operating processes are further described in conjunction with the flow chart of FIG. 7.  
         [0048]    In a preferred embodiment of the present invention, transducer  5   a  includes a piezo-electric crystal within a hand piece, and a dental scaler that is placed at the end of the hand piece. When the power is turned on, the piezo-electric device begins to vibrate and causes the scaler tip to vibrate, wherein the vibrations of the tip are used for example to scrape teeth.  
         [0049]    [0049]FIG. 5 provides a functional diagram for microcontroller  3 . When the microcontroller  3  is powered-up and foot switch node  11  is OFF, all of the outputs are at a logical “0” state.  
         [0050]    The moment that foot switch node  11  is switched ON, and acknowledge signal  19  remains high (logical “1”), outputs  12 ,  13  initially provide output signals oscillating at a starting frequency f start . Starting frequency f start  is then stepped in predetermined increments as shown, for example, during the scanning frequency period  30  of FIG. 4D. This process continues until acknowledge signal  19  is brought to a logical “0,” at which point the scanning or stepping process is disabled. When scanning is disabled, the currently selected frequency is provided by microcontroller  3  until foot switch node  11  is switched OFF.  
         [0051]    As illustrated in FIG. 5, when a logical “0” is applied to node  11 , counter A is loaded, via synchronizer C, with frequency preset  22 . Frequency preset  22  represents the desired starting frequency f start  Counter A presents the frequency preset  22  onto its 16-bit output bus. Synchronizer C loads that data into counter B, which presents that data onto its 16-bit output bus, and enables counter B to begin its count. When counter B completes its count, it triggers flip-flop E, which in turn supplies a logical “1” to counter P, to a reset of counter G, and through an inverter a logical “0” to a reset of counter H.  
         [0052]    Counter G and counter H are configured with a predetermined delay between their outputs (as earlier described with reference to the inset figure of FIGS. 4B, 4C). This delay contributes to a separation of on and off time between the outputs, which operate alternately to each other with each completed count. As illustrated by FIGS. 4B, 4C, and with reference to FIG. 2, signal pulses produced at nodes  12 ,  13  alternatively and respectively drive transistors Q 2 , Q 1  of driver  4  in order to generate an alternating current through nodes  14 ,  15  for operating transformer T 1  of piezo transducer  5  (a). The delay eliminates switching noise that might be otherwise elevated by simultaneously operating transistors Q 2 , Q 1  in an “ON” state.  
         [0053]    Counter J and acknowledge confirmed circuit K monitor the acknowledge signal  19 . Once acknowledge signal  19  is confirmed, the output of acknowledge confirmed circuit K triggers flip-flop L and disables comparator D. Comparator D sends a logical “0” to counter A, and disables any further change to its output. As a result, the microcontroller locks outputs  12 ,  13  at the currently selected frequency.  
         [0054]    Near the time that operation of microcontroller  3  is initiated by start signal  11 , it is possible that a false acknowledge signal  19  could terminate the scanning frequency operation of microcontroller  3 . In order to avoid this possibility, digital noise eliminator M controls operation of counter J at initiation. While start signal  11  has not been provided, eliminator M disables counter J. After start signal  11  is provided, eliminator counts several time periods (for example, totaling on the order of a few milliseconds) before enabling counter J.  
         [0055]    Acknowledge input  19  is primarily designed fir the purpose of having load device  5 ( a ) feed balk a resonate signal to the microcontroller  3  to disable the scanning process once the scanning frequency has reached a resonate or optimum frequency for the load device. Once the scanning process is disabled, the currently selected output frequency is locked by microcontroller  3  for continued operation. Thus, the load device is powered at this point at a resonate frequency, which a lows the load device to operate at its best performance.  
         [0056]    An output signal “Transducer out of range” is provided by maximum frequency decoder N at node  21  to indicate that the transducer load (piezo or electromechanical device) is defective. This output will be active only if the scanning frequency reaches a predetermined limit and the acknowledge signal  19  remains at a logical “1”.  
         [0057]    As earlier described with reference to FIGS. 2, 4B and  4 C, typical push-pull or bridge output drivers  4  of FIG. 2 may experience current switching noise, for example, as one transistor driver Q 1  could switch on at the exact time the other transistor driver Q 2  switches off. As a result, it is quite conceivable that both drivers could be on the same time. The outputs  12 ,  13  of the microcontroller  3  of FIG. 5 are designed to drive driver  4  so that there is no overlap in on/off relationship. A suitable separation between on and off output drive signals at nodes  12 ,  13  is provided, for example, by microcontroller  3  (see, for example, the inset in FIG. 5 illustrating 200 nanoseconds of separation provided by microcontroller  3 ). This separation is achieved as a result of output timing delays provided by counters G, H.  
         [0058]    In addition to providing a mechanism for selecting and operating an ultrasonic driver at an optimum frequency and driver current, the present invention provides an additional operational advantage over the prior art which is herewith explained. FIG. 6 illustrates a typical prior art feedback driver circuit  60  for a piezo transducer. In the circuit of FIG. 6, feedback circuit  63  provides an oscillatory signal to the gate of transistor  61  that permits an oscillatory current flow through transistor  61  in order to cause an oscillatory voltage to appear across a primary winding of transformer  67 . This oscillatory voltage induces an oscillatory voltage in a secondary winding of the transformer  67 , which drives piezo transducer  65 . Impedance characteristics of transducer  65  affect the oscillatory signal provided by feedback circuit  63 .  
         [0059]    For example, if a mechanical force is applied to the piezo transducer  65 , the impedance of transducer  65  increases, and the output current through the secondary winding of transformer  67  decreases, and thereby, the feedback current produced by feedback circuit  63  decreases. If sufficient mechanical force is applied to transducer  65 , the feedback current may decrease below a minimum level required to cause an oscillatory current through transistor  61  (according to Nyquist&#39;s criteria). In this case, the circuit  60  ceases to oscillate, and transducer  65  effectively stalls.  
         [0060]    With reference to FIG. 2, in sharp contrast) Applicants&#39; invention does not employ transducer-based feedback in order to regulate the operating frequency of the transducer. Rather, Applicants&#39; invention employs microcontroller  3  and driver  4  to operate piezo element PE of transducer  5 ( a ) over a range of possible frequencies, detects an optimal frequency via transducer performance detector  6 , and locks the operating frequency at the optimum via microcontroller  3 . In other words, microcontroller  3  regulates operating frequency without using ongoing feedback from piezo element PE of transducer  5 ( a ). As a result, and unlike the prior art, Applicants&#39; driver will not stall in the event that a significant mechanical force is applied to piezo element PE of transducer  5 ( a ).  
         [0061]    [0061]FIG. 7 illustrates a method  700  associated with a preferred embodiment of the present invention. The method begins at step  702  with power being applied to the associated circuitry. In step  704 , a foot switch is operated to initialize the frequency selection process. In step  706 , microcontroller  3  proceeds to provide an initial operating frequency to driver circuit  4 . Typically, this will be a lowest frequency safely below an expected optimum operating frequency for an associated class of transducers. In step  708 , performance of the transducer at the current frequency is monitored as a function of operating current through the transducer. In step  710 , a “chase effect” detection method (as described earlier) is employed to determine whether the operating current has reached a maximum or peak value. If a maximum has not been reached, the frequency is incremented by a predetermined amount in step  712 . Alternatively, in an analogous method beginning with a frequency safely above an expected optimal operating frequency for the transducer class, the frequency is decremented by a predetermined amount in step  712 .  
         [0062]    As long as a boundary limiting frequency is not detected in step  718 , steps  706 ,  708 ,  710 ,  712  and  718  continue to cycle until an operating current maximum is detected in step  710 . The boundary limiting condition may be a maximum operating frequency limit if microcontroller  3  is scanning by incrementing frequency, or may be a minimum operating frequency limit if microcontroller  3  is scanning by decrementing frequency.  
         [0063]    Once maximum current is detected in step  710 , an associated frequency is selected (locked) for operation in step  714 , and the associated transducer is driven at the locked frequency in step  716 . Alternatively, if a boundary limiting frequency is detected in step  718 , a transducer defect signal is produced at node  21  of microcontroller  3  (as earlier described with reference to FIG. 2). The signal at node  21  may be used, for example, to light a lamp for visually indicating this contrition to a user.  
         [0064]    A system and method has been shown in the above embodiments for the effective implementation of an ultrasonic driver. While various preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications and alternate constructions falling within the spirit and scope of the invention, as defined in the appended claims. For example, the present invention should not be limited by type of transducer, order of scanned frequency, specific hardware, or software/program driving the device.