CA1298381C - Piezoelectric phase locked loop circuit - Google Patents
Piezoelectric phase locked loop circuitInfo
- Publication number
- CA1298381C CA1298381C CA000580491A CA580491A CA1298381C CA 1298381 C CA1298381 C CA 1298381C CA 000580491 A CA000580491 A CA 000580491A CA 580491 A CA580491 A CA 580491A CA 1298381 C CA1298381 C CA 1298381C
- Authority
- CA
- Canada
- Prior art keywords
- signal
- phase
- output
- piezoelectric
- structural member
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H13/00—Measuring resonant frequency
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/0207—Driving circuits
- B06B1/0223—Driving circuits for generating signals continuous in time
- B06B1/0238—Driving circuits for generating signals continuous in time of a single frequency, e.g. a sine-wave
-
- G—PHYSICS
- G08—SIGNALLING
- G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- G08B13/00—Burglar, theft or intruder alarms
- G08B13/16—Actuation by interference with mechanical vibrations in air or other fluid
- G08B13/1609—Actuation by interference with mechanical vibrations in air or other fluid using active vibration detection systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
- B06B2201/50—Application to a particular transducer type
- B06B2201/55—Piezoelectric transducer
- B06B2201/56—Foil type, e.g. PVDF
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B2201/00—Indexing scheme associated with B06B1/0207 for details covered by B06B1/0207 but not provided for in any of its subgroups
- B06B2201/70—Specific application
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S331/00—Oscillators
- Y10S331/02—Phase locked loop having lock indicating or detecting means
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S73/00—Measuring and testing
- Y10S73/04—Piezoelectric
Abstract
PIEZOELECTRIC PHASE LOCKED LOOP CIRCUIT
Abstract of the Disclosure A structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto. The transmitter film produces a vibration upon activation by a voltage controlled oscillator which forms part of a phase-lock loop circuit. The vibrations of the rigid member generate electric signals on a second receiver film, which feed into a phase comparator.
The other input of the phase comparator is the voltage controlled oscillator. The phase comparator will output a dc signal proportional to the difference in phase between the two signals. When the structural member becomes damped the phase comparator will go into saturation, thereby producing a voltage which can activate an alarm signal or other device.
Abstract of the Disclosure A structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto. The transmitter film produces a vibration upon activation by a voltage controlled oscillator which forms part of a phase-lock loop circuit. The vibrations of the rigid member generate electric signals on a second receiver film, which feed into a phase comparator.
The other input of the phase comparator is the voltage controlled oscillator. The phase comparator will output a dc signal proportional to the difference in phase between the two signals. When the structural member becomes damped the phase comparator will go into saturation, thereby producing a voltage which can activate an alarm signal or other device.
Description
PIEZOELECTRIC PHASE LOC~ED L~OP CIRCUIT
Backqround of the Invention A phase-locked loop is an electronic circuit used to lock an oscill~tor in phase with an arbitrary input signal.
Typically, phase-locked loops comprise a phase comparator, a low pass filter and an error amplifier in the forward signal path with a voltage control oscillator (VCO) in the feedback path. The function of the VCO is to produce a signal which will act as a reference to the phase comparator, and also track any phase change in the input signal. The frequency of the VCO output is controlled by a dc error signal which is generated by the phase comparator.
The dc error signal generated is proportional to the difference in the phase angle between the VCO and the reference input signal.
An important performance Parameter of a phase locked loop is its hold-in range. The hold-in range is the maximum change in input frequency for which the loop will remain locked. It is governed by the dc gain of the loop.
As the frequency of the input signal is changed, the differential in phase of the two signals inputted to the phase detector will produce a dc voltage which will change the output ~requency of the VCO. As the input frequency is further altered, the phase angle differential will continue to increase until it reaches a point where the loop unlocks.
~k 12~8;}~1 Phase lock loops have numerous applications. While phase locked loo~s are perha~s most widely utilized in television receivers, they can ~e adapted to almost any application requiring frequency de~odulation. ~t is well known, for example, that a rigid structure such as a cantilevered beam will vibrate at a characteristic resonant frequency. This frequency is dependent upon the len~th, width, geometric and structural characteristics of the member with respect to the specific point or node where it is held rigid. In the case of a fixed cantilevered-beam, maximum oscillatory deflection will occur at the free end.
By damping the free end of a vibrating cantilevered beam, the resonant frequency of vibration will increase and the phase of vibration of the structure will be shifted positive.
A vibrating rigid member can be utilized to produce an input signal for a phase-locked loop circuit. By utilizing one output of the VCO as a driving signal, a rigid member can be made to vibrate at a characteristic frequency. An input signal generated directly from the driven ri~id member can then be utilized as an input to a phase comparator in the phase-locked loop. If the vibrating member is deflected or damped, thereby increasing its frequency, the phase of the input signal fed to the phase comparator will change. This phase change will produce a positive output on the phase comparator which will geRera.e a correc~ve dc e~Lor sigrlal to trle VCû. ~h~
VCO will accordingly attempt to track the change in input phase. If the phase differential ultimately exceeds the hold-in range of the circuit, the loop will unlock~
Piezoelectric films generally have been thought to ~e unsuited for sensing constant or slowly changing conditions such as the phase changes characteristic of phase-locked loop circuits. New circuit techniques, however~ permit J ~98;~15 1 piezoelectric films to detect steady-state and slowly changing conditions. These new techniques permit the film to he utilized in association with a vibrating member for use in a phase-locked loop circuit.
Kynar'~ piezoelectric film, a commercially available product of Pennwalt Corporation, Philadelphia, PA, assignee of the ~resent invention has excellent electro-mechanical properties which make it ideal as a transducer material for use in association with a vibrating rigid member. When a voltage of proper polarity is appl;ed to a sheet of piezoelectric film, the film becomes thinner and elonqates.
If a voltage of opposite polarity is applied, the film accor~inqly contracts (or shortens) and simultaneously thickens. Accordingly, if directly adhered to a rigid member, the electro-mechanical property of Kynar~ piezo film can be utilized to generate mechanical vibration in the riqid member upon application of an ac signal.
Correspondingly, the mechano-electrical properties of Kynar~ piezo film make it ideal as a transducer for generating an ac input signal for the phase-locked loop.
When an external force (such as the mechanical vibration induced in a rigid member) produces compressive and tensile strain in a second film, an electric potential proportional to the change in mechanical stress is produced across the film. When the direction of force is reversed, the polarity of the resulting voltage is reversed. Hence, the vibrations of the beam geneLated by a first fiim resuits in an alternating voltage in a second film which can be used as an input signal in a phase locked loop circuit. Kynar~
piezoelectric film is sensitive enough such that stretching of a mere 5-10 micrometers can yield voltage outputs ranqing from 10-1000 volts.
It is an object of the present invention to utilize Kynar~ piezo film in order to generate vibration in a riqid 8.~
structural member and to utilize that vibration to produce ~ correspondinc1 in~ut siqnal for a phase locked loop circuit.
It is ~nother object o~ the present invention to utilize Kynar~ piezo film in order to generate an input signal for a phase-locked loop circuit which can be used for practical applications such as in an alarm syste~, liquid level detector.
ummary of the Invention In accordance with the invention, a piezoelectric phase-lock loop circuit is disclosed. The circuit comprises a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, the transmitter film producing electro-mechanical vibrations in the structural member upon activation by an alternatinq current input signal, the receiver film producing alternating output signals upon vibration of said rigid member. A voltage control oscillator (VCO) means generates the alternating input signal. A phase com~arator means compares the phase angle of the si~nal produced by the receiver film with the phaseangle of the VCO generated input signal ~nd a low pass filter means connected to ~he output of the phase comparator means inputs a dc error sianal to the voltage control oscillator (VCO) means.
The dc error signalclrives the freguency of the voltage controlled oscillator (VCO) so as to track the phase of the said input signal whereby 2 predetermined phase relationship is maintained between the output and input signals.
_rief ~escription of The Drawings Figure 1 is a section view o~ the beam member of a preferred embodimentof the invention.
Figure lA is a perspective view of a fluid-level detector utilizing the piezoelectric phase-locked loop.
3~
.
Figure 2 i5 a schematic representation of a signal system incorporating the phase-lock loop of the preferred embodiment.
Figure 3 (on the sheet containing Fi7ure 1) is a block ~iagram of the phase-~ock loop of the preferred embodiment.
Figure 4 is a block diagram of an alarm system incorporating the phase lock loop of the preferred embodiment.
Figure 5 is a block diagram of an alternative embodiment of the alarm system incorporating a one shot mode.
Description of the Preferred Embodiment The invention is described with reference to the enclosed Figures wherein the same numbers are used where applicable. Referring to Figure 1, a rigid beam 10 with one end permanently fixed is shown. Ream 10 is a simple resonant structure. One end is clamped while .he other is free to move. When the structure is disturbed with a force impulse at its free end 10a, beam 10 will vihrate at a characteristic resonant ~requency. The beam has respective piezoelectric transmitter and receiver films 12, 12a adhered to opposite sides of its surface. As those skilled in the art will readily understand, piezoelectric film 12, 12a must be coated with a metal such as aluminum, chromium, silver or other electrode metal in order to create a usable electric signal. These coatinqs are generally applied by vacuum deposition.
Beam 10 is excited and caused to vibrate by an output ac signal 14 which, as will be discussed below, is the amplified signal from a voltage control oscillator (VCO).
The output ac signal 14 when applied to the electrode of piezoelectric transmitter film 12, causes transmitter film 12 to alternatingly elongate and contract. These alternating deformations generate vibrations in beam 10.
s~
The vibrations of the beam, in turn, result in alternating mechanical stress in receiver ~ilm 12a. The alternatin~
stresses in receiver ~ilm 12a, caused by the vibrations of beam 10, qenerate an ac in~ut signal 16. When the beam is vibrating at a resonant frequency, the output and input signals will operate at the same frequency, with a 0 phase of~set. As shown in Figure 1, the respective transmitter and receiver films 12, 12a are glued to opposing surfaces of the beam. However, the ~ s can be adhered directly to each other, and therefore operate as their own vib~ating ~ember.
Referring to Fiqure 2, the electronic circuitry of the preferred embodiment is disclosed. The ac signal 16 generated by receiver film 12a is fed through current amplifier 18 which minimizes the effects of cabling and lead capacitances. Current amplifier 18 shifts the ~hase of the input signal by 90 degrees, thereby eliminating the need for a separate phase shi~ter.
The output o~ current amplifier 18 is then fed through high-pass filter/amplifier 20 which removes the low ~requency noise generated by current amplifier 18. High pass filter/amplifier 20 provides gain but at a pass frequency of approximately two-thirds that of the resonant ~requency of beam 10. This frequency provides the best performance for the circuit. A second filter 22 having the same pass frequency as high ~ass filter/amplifier 20, ~rovides two pole filtering. This particular componen- is not vital to the circuit. The degree of filtering can be modified depending upon the resonant frequency of the beam.
Referrin~ to Figure 3, the phase lock loop circuit of the preferred embodiment is described. Initially, the output of filter 22 is fed into limiter 24 which holds the signal to a preselected level, e.g. 200 millivolts. The output of limiter 24, which is proportional to the ac ~2~8.~
si~nal ~enerated ~y receiver film 12a, is fed as one input into phase comparator 26. Phase comparator 26 of the preferred e~bodiment is a conventional component. Two commonly known phase comparators which can be utilized in the present invention are the diode phase comparator and the double-balanced phase comparator. The diode phase comparator has been preferred historically because of its lower cost and better performance at higher frequencies.
The second input of phase comparator 26 is the output of VCO 28, which comprises the feedback loop of the circuit. VCO 28 is also a conventional component. Two common types of VCOs which can be applied in the circuit of the present invention are the reactance modulator and the varactor modulator. Another popular VCO utilizes a multivibrator wherein a timing capacitor charging current is varied by a dc control voltage. The output of the vCO
28 drives transmitter film 12a through amplifier 30, which provides unity gain and a 0 phase shift.
The output of VCO 28 is then compared with the phase shifted ac siqnal 16 generated by the receiver film 12a.
The output of phase detector 26 is fed into low pass filter ?1. The frequency of the low-pass filter 31 determines the trequency response of the phase-lock loop. Low-pass filter ?l filters out the hi,qh frequency component of the phase-co~parator output and passes the dc response to VCO 28. In phase-lock, low-pass filter 31 passes a dc volta~e corresponding to the phase differential betweer. the OU~L~
of VCO 28 and output signal 16 generated by the receiver film 12a.
A phase differential of approximately -0- (zero) corresponds to a condition of undamped resonance in the beam member. If the resonant frequency of vibration of beam 10 increases due to da~ping, the phase of input signa1 16 fed throughthe phase co~rator 26 will shift positively.
1;Z98;31~3~
If the ~requency of vibration o~ the beam drops due to un~amping, the phase o~ input signal 16 shifts in a negative direction. In either situation, a dc error signal corresponding to the phase shift will be passed as a dc voltage to VCo 28 through a low pass filter 31. VCO ~8 will attem~t to track the change in phase of the input signal.
Ideally, the phase-lock loop should be desi~ned to have an operating range between pre-set hi~h and low limits. It is optimal to have a narrow hold-in range on the phase-lock loop, yet one which is broad enough so as to keep the loop locked through minor disturbances.
Accordingly, as long as beam iO is not significantly damped (or und~mped), the circuit should remain within its hold-in range. When, for example, beam 10 is significantly damped, the circuit will be forced out of its hold-in range.
Significant damping will force phase comparator 26 and l~w pass ~ilter 31 into saturation.
The operation of beam 10 in conjunction with the phase-lock 1Oop circuit is now described with referenceto Figures 1 and 2. When the system is first powered up, beam 10 is assumed not to be vibrating. Therefore, input s,ignal 16 will approximate a zero output. Phase comparator 26 will produce a voltage corresponding to the free runnin~
frequency of VCO 28. Ph~se comparator 26 will output a ~c component which will maintain VCO 28 at its free running frequency. The signal ~rom the ~.~CO 28 will thcn drlve thG
beam through transmitter film 12, thereby initiating vibration in the structure. This vibration will generate an output signal 16 on the receiver film 12a, which will, after amplification and filtering, input to phase detector 26. As input signal 16 increases in amplitude, the system will begin to phase lock, except for a finite phase difference. This phase difference generates a corrective .k 1~98.'3~3~
g error voltage which shifts the VCO frequency fro~ its free running value.
When the resonant frequency of the beam 10 is not the same as the free running frequency of vCo 28, the return signal will be phase shifted in such a way as to generate a dc signal on phase detector 26. This dc component will force the frequency of VCo 28 in the direction of the new resonant frequency. The output frequency of VCO 28 will change until the phase difference between VCo 28 and the input si~nal 16 is minimized. When loc~ed on the resonant frequency of the beam, the output of phase detector 26 will approach 0 (zero).
The resonant beam and phase lock loop circuitry can be combined with circuitry which will indicate when the phase locked loop is unlocked. This circuitry facilitates the practical application of the circuit. Referring to Fi~ures 2, 3 and 4, pin 6 of the phase-lock loop is a dc reference voltage (both positive and negative) which tracks the output of low-pass filter 31 to a predetermined maximum hold-in level for the system. The reference si~nal can be produced by a limiter which tracks the output of VCo 28 until it reaches a preselected value corresponding to a preselected hold-in level. Pin 7 is the dc voltage produced by low-pass filter 3q. The preselected hold-in level must be slightly below that of the maximu~ voltage level of pin 7. This maximum level will in practical terms correspond to saturation of the phase comparator 26 an~
low-pass filter 31. Pins 6 and 7 input to a differential amplifier 32. The output voltage of the differential amplifier 32 then indicates whether the circuit is in phase-lock. This output differential amPlifier 32 will approach 0 (zero) volts when the phase-lock loop remains locked, i.e when the output of pin 6 equals the output of pin 7. When the loop unlocks the value of pin 7 will 905-1~1 ~;~983~1 - 1 o -exceed that of ~in 6 (either positive or negative) and differential a~nlifier 32 will output a non-zero value.
The output of differential amplifier 32 is then ~ed through a pair of comparators 34, 36 in a "wired-or" configuration.
The use of the "wired-or" configuration per~its the circuit to activate on either a positive or negative output on differential amplifier 32. Thus, for example, if the loop is pulled out of range high, comparator 34, for example, goes low. Indicating means such as LED 38 will light thereby indicating that th~ circuit is out of lock.
If the circuit unlocks low, then comparator 36, goes low, again causing LED 38 to light. In either event, if the system is pulled out of phase lock, the "wired-or"
comparator configuration will output a value which will cause LED 38 to light.
The present invention suggests numerous practical applications of which the following are examples. First, the circuit can be utilized in an alarm system. In such a syste~, an undamped vibrating beam member such as beam member 10 could be attached in proximity to a window or door. The opening of the window or door by an intruder could activate means which significantly dampen beam 10, thereby increasing the resonant frequency of beam so as to shift the phase of input signal 16. The change in input phase when compared with the phase of the VCO 28 will generate an error signal which will be fed back to the VCO.
The error signal increases the fre~uency of VCG so dS to track the input signal. The dc output of the phase detector will feed to a differential amplifier where it is compared with a second tracking reference signal. As a predetermined point is reached, the second tracking signal will be li~ited thereby producing positive output on the differential amplifier. The output of the differential amplifier can be used to generate an output signal. As ,,~
l;;~9B381 noted previously, the phase shift can change either be positive or negative. Thus, the loop can be set to stay phase-lockeduntil openin~ of the windcw or door can un~n the resonant structure and thereby unlock the loop.
Those skilled in the art will readily recognize that the principles of applicant's piezoelectric phase-lock loop can be a~Dlied to any vibrating structure or member. Thus, referring to Figure lA, the circuit can be applied, for example, to a liquid detector. In this application the transmitter fil~ 12' is used to generate vibration in a beaker or vessel 40. The vibrations generate an output signal in receiver film 12a'. The addition of liquid will dampen or change the resonant frequency of the beaker 40.
Incorporatin~ the circuitryo~ the phase-l ~ ed loop ~d siqnaling circuitry of Figures 2 and 3, the piezoelectric phase-l ~ ed 100~D circuit can be designed with a hold-in range such that the circuit stays locked until a liguid reaches a pre-set level in the beaker. Upon reaching the pre-set level, the circuit would unlock, thereby activating indicating or activation circuitry. As those skilled in the art will readily discern, the circuit can be applied to any application where a change in pressure in a member alters its resonant frequency.
In an alternative embodirnent, the invention operates in a one-shot mode. In this embodiment switchesSWl, 42, 42a are depressed downwardthereby by passing the phase-locKea loop and differential amplifier circuitry. Upon activation of the beam member 10 an electronic output signal is generated. The signal passes through current amplifier 18, high pass filter/amplifier 20 and second filter 22. The signal inputs into a one-shot44. me one-sho~ 44 indicates whether the switch has been "twangedn. The output of the ,,:~
1~98;~
one-shot then can be fed to an invertor bu~fer46 which produces an output signal on LED 38.
While the applicant has disclosed two e~bodiments o~
the invention, it will be readily understood by those skilled in the art that other embodiments than those disclosed all within the spirit and scope of the claims attached hereto.
~'~
Backqround of the Invention A phase-locked loop is an electronic circuit used to lock an oscill~tor in phase with an arbitrary input signal.
Typically, phase-locked loops comprise a phase comparator, a low pass filter and an error amplifier in the forward signal path with a voltage control oscillator (VCO) in the feedback path. The function of the VCO is to produce a signal which will act as a reference to the phase comparator, and also track any phase change in the input signal. The frequency of the VCO output is controlled by a dc error signal which is generated by the phase comparator.
The dc error signal generated is proportional to the difference in the phase angle between the VCO and the reference input signal.
An important performance Parameter of a phase locked loop is its hold-in range. The hold-in range is the maximum change in input frequency for which the loop will remain locked. It is governed by the dc gain of the loop.
As the frequency of the input signal is changed, the differential in phase of the two signals inputted to the phase detector will produce a dc voltage which will change the output ~requency of the VCO. As the input frequency is further altered, the phase angle differential will continue to increase until it reaches a point where the loop unlocks.
~k 12~8;}~1 Phase lock loops have numerous applications. While phase locked loo~s are perha~s most widely utilized in television receivers, they can ~e adapted to almost any application requiring frequency de~odulation. ~t is well known, for example, that a rigid structure such as a cantilevered beam will vibrate at a characteristic resonant frequency. This frequency is dependent upon the len~th, width, geometric and structural characteristics of the member with respect to the specific point or node where it is held rigid. In the case of a fixed cantilevered-beam, maximum oscillatory deflection will occur at the free end.
By damping the free end of a vibrating cantilevered beam, the resonant frequency of vibration will increase and the phase of vibration of the structure will be shifted positive.
A vibrating rigid member can be utilized to produce an input signal for a phase-locked loop circuit. By utilizing one output of the VCO as a driving signal, a rigid member can be made to vibrate at a characteristic frequency. An input signal generated directly from the driven ri~id member can then be utilized as an input to a phase comparator in the phase-locked loop. If the vibrating member is deflected or damped, thereby increasing its frequency, the phase of the input signal fed to the phase comparator will change. This phase change will produce a positive output on the phase comparator which will geRera.e a correc~ve dc e~Lor sigrlal to trle VCû. ~h~
VCO will accordingly attempt to track the change in input phase. If the phase differential ultimately exceeds the hold-in range of the circuit, the loop will unlock~
Piezoelectric films generally have been thought to ~e unsuited for sensing constant or slowly changing conditions such as the phase changes characteristic of phase-locked loop circuits. New circuit techniques, however~ permit J ~98;~15 1 piezoelectric films to detect steady-state and slowly changing conditions. These new techniques permit the film to he utilized in association with a vibrating member for use in a phase-locked loop circuit.
Kynar'~ piezoelectric film, a commercially available product of Pennwalt Corporation, Philadelphia, PA, assignee of the ~resent invention has excellent electro-mechanical properties which make it ideal as a transducer material for use in association with a vibrating rigid member. When a voltage of proper polarity is appl;ed to a sheet of piezoelectric film, the film becomes thinner and elonqates.
If a voltage of opposite polarity is applied, the film accor~inqly contracts (or shortens) and simultaneously thickens. Accordingly, if directly adhered to a rigid member, the electro-mechanical property of Kynar~ piezo film can be utilized to generate mechanical vibration in the riqid member upon application of an ac signal.
Correspondingly, the mechano-electrical properties of Kynar~ piezo film make it ideal as a transducer for generating an ac input signal for the phase-locked loop.
When an external force (such as the mechanical vibration induced in a rigid member) produces compressive and tensile strain in a second film, an electric potential proportional to the change in mechanical stress is produced across the film. When the direction of force is reversed, the polarity of the resulting voltage is reversed. Hence, the vibrations of the beam geneLated by a first fiim resuits in an alternating voltage in a second film which can be used as an input signal in a phase locked loop circuit. Kynar~
piezoelectric film is sensitive enough such that stretching of a mere 5-10 micrometers can yield voltage outputs ranqing from 10-1000 volts.
It is an object of the present invention to utilize Kynar~ piezo film in order to generate vibration in a riqid 8.~
structural member and to utilize that vibration to produce ~ correspondinc1 in~ut siqnal for a phase locked loop circuit.
It is ~nother object o~ the present invention to utilize Kynar~ piezo film in order to generate an input signal for a phase-locked loop circuit which can be used for practical applications such as in an alarm syste~, liquid level detector.
ummary of the Invention In accordance with the invention, a piezoelectric phase-lock loop circuit is disclosed. The circuit comprises a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, the transmitter film producing electro-mechanical vibrations in the structural member upon activation by an alternatinq current input signal, the receiver film producing alternating output signals upon vibration of said rigid member. A voltage control oscillator (VCO) means generates the alternating input signal. A phase com~arator means compares the phase angle of the si~nal produced by the receiver film with the phaseangle of the VCO generated input signal ~nd a low pass filter means connected to ~he output of the phase comparator means inputs a dc error sianal to the voltage control oscillator (VCO) means.
The dc error signalclrives the freguency of the voltage controlled oscillator (VCO) so as to track the phase of the said input signal whereby 2 predetermined phase relationship is maintained between the output and input signals.
_rief ~escription of The Drawings Figure 1 is a section view o~ the beam member of a preferred embodimentof the invention.
Figure lA is a perspective view of a fluid-level detector utilizing the piezoelectric phase-locked loop.
3~
.
Figure 2 i5 a schematic representation of a signal system incorporating the phase-lock loop of the preferred embodiment.
Figure 3 (on the sheet containing Fi7ure 1) is a block ~iagram of the phase-~ock loop of the preferred embodiment.
Figure 4 is a block diagram of an alarm system incorporating the phase lock loop of the preferred embodiment.
Figure 5 is a block diagram of an alternative embodiment of the alarm system incorporating a one shot mode.
Description of the Preferred Embodiment The invention is described with reference to the enclosed Figures wherein the same numbers are used where applicable. Referring to Figure 1, a rigid beam 10 with one end permanently fixed is shown. Ream 10 is a simple resonant structure. One end is clamped while .he other is free to move. When the structure is disturbed with a force impulse at its free end 10a, beam 10 will vihrate at a characteristic resonant ~requency. The beam has respective piezoelectric transmitter and receiver films 12, 12a adhered to opposite sides of its surface. As those skilled in the art will readily understand, piezoelectric film 12, 12a must be coated with a metal such as aluminum, chromium, silver or other electrode metal in order to create a usable electric signal. These coatinqs are generally applied by vacuum deposition.
Beam 10 is excited and caused to vibrate by an output ac signal 14 which, as will be discussed below, is the amplified signal from a voltage control oscillator (VCO).
The output ac signal 14 when applied to the electrode of piezoelectric transmitter film 12, causes transmitter film 12 to alternatingly elongate and contract. These alternating deformations generate vibrations in beam 10.
s~
The vibrations of the beam, in turn, result in alternating mechanical stress in receiver ~ilm 12a. The alternatin~
stresses in receiver ~ilm 12a, caused by the vibrations of beam 10, qenerate an ac in~ut signal 16. When the beam is vibrating at a resonant frequency, the output and input signals will operate at the same frequency, with a 0 phase of~set. As shown in Figure 1, the respective transmitter and receiver films 12, 12a are glued to opposing surfaces of the beam. However, the ~ s can be adhered directly to each other, and therefore operate as their own vib~ating ~ember.
Referring to Fiqure 2, the electronic circuitry of the preferred embodiment is disclosed. The ac signal 16 generated by receiver film 12a is fed through current amplifier 18 which minimizes the effects of cabling and lead capacitances. Current amplifier 18 shifts the ~hase of the input signal by 90 degrees, thereby eliminating the need for a separate phase shi~ter.
The output o~ current amplifier 18 is then fed through high-pass filter/amplifier 20 which removes the low ~requency noise generated by current amplifier 18. High pass filter/amplifier 20 provides gain but at a pass frequency of approximately two-thirds that of the resonant ~requency of beam 10. This frequency provides the best performance for the circuit. A second filter 22 having the same pass frequency as high ~ass filter/amplifier 20, ~rovides two pole filtering. This particular componen- is not vital to the circuit. The degree of filtering can be modified depending upon the resonant frequency of the beam.
Referrin~ to Figure 3, the phase lock loop circuit of the preferred embodiment is described. Initially, the output of filter 22 is fed into limiter 24 which holds the signal to a preselected level, e.g. 200 millivolts. The output of limiter 24, which is proportional to the ac ~2~8.~
si~nal ~enerated ~y receiver film 12a, is fed as one input into phase comparator 26. Phase comparator 26 of the preferred e~bodiment is a conventional component. Two commonly known phase comparators which can be utilized in the present invention are the diode phase comparator and the double-balanced phase comparator. The diode phase comparator has been preferred historically because of its lower cost and better performance at higher frequencies.
The second input of phase comparator 26 is the output of VCO 28, which comprises the feedback loop of the circuit. VCO 28 is also a conventional component. Two common types of VCOs which can be applied in the circuit of the present invention are the reactance modulator and the varactor modulator. Another popular VCO utilizes a multivibrator wherein a timing capacitor charging current is varied by a dc control voltage. The output of the vCO
28 drives transmitter film 12a through amplifier 30, which provides unity gain and a 0 phase shift.
The output of VCO 28 is then compared with the phase shifted ac siqnal 16 generated by the receiver film 12a.
The output of phase detector 26 is fed into low pass filter ?1. The frequency of the low-pass filter 31 determines the trequency response of the phase-lock loop. Low-pass filter ?l filters out the hi,qh frequency component of the phase-co~parator output and passes the dc response to VCO 28. In phase-lock, low-pass filter 31 passes a dc volta~e corresponding to the phase differential betweer. the OU~L~
of VCO 28 and output signal 16 generated by the receiver film 12a.
A phase differential of approximately -0- (zero) corresponds to a condition of undamped resonance in the beam member. If the resonant frequency of vibration of beam 10 increases due to da~ping, the phase of input signa1 16 fed throughthe phase co~rator 26 will shift positively.
1;Z98;31~3~
If the ~requency of vibration o~ the beam drops due to un~amping, the phase o~ input signal 16 shifts in a negative direction. In either situation, a dc error signal corresponding to the phase shift will be passed as a dc voltage to VCo 28 through a low pass filter 31. VCO ~8 will attem~t to track the change in phase of the input signal.
Ideally, the phase-lock loop should be desi~ned to have an operating range between pre-set hi~h and low limits. It is optimal to have a narrow hold-in range on the phase-lock loop, yet one which is broad enough so as to keep the loop locked through minor disturbances.
Accordingly, as long as beam iO is not significantly damped (or und~mped), the circuit should remain within its hold-in range. When, for example, beam 10 is significantly damped, the circuit will be forced out of its hold-in range.
Significant damping will force phase comparator 26 and l~w pass ~ilter 31 into saturation.
The operation of beam 10 in conjunction with the phase-lock 1Oop circuit is now described with referenceto Figures 1 and 2. When the system is first powered up, beam 10 is assumed not to be vibrating. Therefore, input s,ignal 16 will approximate a zero output. Phase comparator 26 will produce a voltage corresponding to the free runnin~
frequency of VCO 28. Ph~se comparator 26 will output a ~c component which will maintain VCO 28 at its free running frequency. The signal ~rom the ~.~CO 28 will thcn drlve thG
beam through transmitter film 12, thereby initiating vibration in the structure. This vibration will generate an output signal 16 on the receiver film 12a, which will, after amplification and filtering, input to phase detector 26. As input signal 16 increases in amplitude, the system will begin to phase lock, except for a finite phase difference. This phase difference generates a corrective .k 1~98.'3~3~
g error voltage which shifts the VCO frequency fro~ its free running value.
When the resonant frequency of the beam 10 is not the same as the free running frequency of vCo 28, the return signal will be phase shifted in such a way as to generate a dc signal on phase detector 26. This dc component will force the frequency of VCo 28 in the direction of the new resonant frequency. The output frequency of VCO 28 will change until the phase difference between VCo 28 and the input si~nal 16 is minimized. When loc~ed on the resonant frequency of the beam, the output of phase detector 26 will approach 0 (zero).
The resonant beam and phase lock loop circuitry can be combined with circuitry which will indicate when the phase locked loop is unlocked. This circuitry facilitates the practical application of the circuit. Referring to Fi~ures 2, 3 and 4, pin 6 of the phase-lock loop is a dc reference voltage (both positive and negative) which tracks the output of low-pass filter 31 to a predetermined maximum hold-in level for the system. The reference si~nal can be produced by a limiter which tracks the output of VCo 28 until it reaches a preselected value corresponding to a preselected hold-in level. Pin 7 is the dc voltage produced by low-pass filter 3q. The preselected hold-in level must be slightly below that of the maximu~ voltage level of pin 7. This maximum level will in practical terms correspond to saturation of the phase comparator 26 an~
low-pass filter 31. Pins 6 and 7 input to a differential amplifier 32. The output voltage of the differential amplifier 32 then indicates whether the circuit is in phase-lock. This output differential amPlifier 32 will approach 0 (zero) volts when the phase-lock loop remains locked, i.e when the output of pin 6 equals the output of pin 7. When the loop unlocks the value of pin 7 will 905-1~1 ~;~983~1 - 1 o -exceed that of ~in 6 (either positive or negative) and differential a~nlifier 32 will output a non-zero value.
The output of differential amplifier 32 is then ~ed through a pair of comparators 34, 36 in a "wired-or" configuration.
The use of the "wired-or" configuration per~its the circuit to activate on either a positive or negative output on differential amplifier 32. Thus, for example, if the loop is pulled out of range high, comparator 34, for example, goes low. Indicating means such as LED 38 will light thereby indicating that th~ circuit is out of lock.
If the circuit unlocks low, then comparator 36, goes low, again causing LED 38 to light. In either event, if the system is pulled out of phase lock, the "wired-or"
comparator configuration will output a value which will cause LED 38 to light.
The present invention suggests numerous practical applications of which the following are examples. First, the circuit can be utilized in an alarm system. In such a syste~, an undamped vibrating beam member such as beam member 10 could be attached in proximity to a window or door. The opening of the window or door by an intruder could activate means which significantly dampen beam 10, thereby increasing the resonant frequency of beam so as to shift the phase of input signal 16. The change in input phase when compared with the phase of the VCO 28 will generate an error signal which will be fed back to the VCO.
The error signal increases the fre~uency of VCG so dS to track the input signal. The dc output of the phase detector will feed to a differential amplifier where it is compared with a second tracking reference signal. As a predetermined point is reached, the second tracking signal will be li~ited thereby producing positive output on the differential amplifier. The output of the differential amplifier can be used to generate an output signal. As ,,~
l;;~9B381 noted previously, the phase shift can change either be positive or negative. Thus, the loop can be set to stay phase-lockeduntil openin~ of the windcw or door can un~n the resonant structure and thereby unlock the loop.
Those skilled in the art will readily recognize that the principles of applicant's piezoelectric phase-lock loop can be a~Dlied to any vibrating structure or member. Thus, referring to Figure lA, the circuit can be applied, for example, to a liquid detector. In this application the transmitter fil~ 12' is used to generate vibration in a beaker or vessel 40. The vibrations generate an output signal in receiver film 12a'. The addition of liquid will dampen or change the resonant frequency of the beaker 40.
Incorporatin~ the circuitryo~ the phase-l ~ ed loop ~d siqnaling circuitry of Figures 2 and 3, the piezoelectric phase-l ~ ed 100~D circuit can be designed with a hold-in range such that the circuit stays locked until a liguid reaches a pre-set level in the beaker. Upon reaching the pre-set level, the circuit would unlock, thereby activating indicating or activation circuitry. As those skilled in the art will readily discern, the circuit can be applied to any application where a change in pressure in a member alters its resonant frequency.
In an alternative embodirnent, the invention operates in a one-shot mode. In this embodiment switchesSWl, 42, 42a are depressed downwardthereby by passing the phase-locKea loop and differential amplifier circuitry. Upon activation of the beam member 10 an electronic output signal is generated. The signal passes through current amplifier 18, high pass filter/amplifier 20 and second filter 22. The signal inputs into a one-shot44. me one-sho~ 44 indicates whether the switch has been "twangedn. The output of the ,,:~
1~98;~
one-shot then can be fed to an invertor bu~fer46 which produces an output signal on LED 38.
While the applicant has disclosed two e~bodiments o~
the invention, it will be readily understood by those skilled in the art that other embodiments than those disclosed all within the spirit and scope of the claims attached hereto.
~'~
Claims (8)
1. A piezoelectric phase-lock loop circuit comprising:
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations in said structural member upon activation by an alternating current input signal, said receiver film producing alternating output signals in response to vibration of said structural member;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle of the signal produced by said receiver film with the phase angle of said alternating input signal and for outputting a signal corresponding to the differential in phase angle;
(d) low pass filter means connected to the output of said phase comparator means for inputting a dc error signal corresponding to said phase differential to said voltage controlled oscillator means, said dc error signal forcing the frequency of said voltage controlled oscillator means to track said output signal whereby a predetermined phase relationship is maintained between said output and input signals.
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations in said structural member upon activation by an alternating current input signal, said receiver film producing alternating output signals in response to vibration of said structural member;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle of the signal produced by said receiver film with the phase angle of said alternating input signal and for outputting a signal corresponding to the differential in phase angle;
(d) low pass filter means connected to the output of said phase comparator means for inputting a dc error signal corresponding to said phase differential to said voltage controlled oscillator means, said dc error signal forcing the frequency of said voltage controlled oscillator means to track said output signal whereby a predetermined phase relationship is maintained between said output and input signals.
2. The piezoelectric phase-lock loop circuit recited in claim 1 further comprising a current amplifying means for shifting the phase of the output signal generated by said receiver film by approximately 90°.
3. The piezoelectric phase-lock loop circuit of claim 2 further comprising amplifier means for amplifying the signal from said voltage controlled oscillator means which drives said transmitter film.
4. The piezoelectric phase-lock loop circuit of claim 1 further comprising:
(a) means for producing a reference signal corresponding to said error signal;
(b) means for producing a tracking signal corresponding to the dc component of said error signal, said tracking signal tracking said reference signal to a point corresponding to said predetermined phase relationship;
(c) differential amplifier means for determining a difference between said reference signal and said tracking signal;
(d) comparator means for registering a signal output when said reference signal exceeds said tracking signal; and (e) signaling means for indicating when said reference signal is not equal to said tracking signal.
(a) means for producing a reference signal corresponding to said error signal;
(b) means for producing a tracking signal corresponding to the dc component of said error signal, said tracking signal tracking said reference signal to a point corresponding to said predetermined phase relationship;
(c) differential amplifier means for determining a difference between said reference signal and said tracking signal;
(d) comparator means for registering a signal output when said reference signal exceeds said tracking signal; and (e) signaling means for indicating when said reference signal is not equal to said tracking signal.
5. The piezoelectric phase-lock loop circuit of claims 1 or 4 where said structural member is a cantilevered beam.
6. The piezoelectric phase-lock loop circuit of Claims 1 or 4 wherein said structural member is a beaker and said predetermined phase relationship is maintained until said beaker fills with a liquid to a pre-set level.
7. An apparatus for detecting a change in the vibrational characteristics of a structural member, comprising:
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations on said structural member upon activation by an alternating current input signal, said receiver film producing an alternating current output signal upon vibration of said structural member;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle differential between said alternating input signal and said alternating current output signal, said phase comparator means generating a signal proportional to said phase angle differential;
(d) low pass filter means for passing an error signal proportional to the signal generated by said phase comparator, said signal proportionally adjusting the frequency of said voltage controlled oscillator to a frequency within a preselected frequency range;
(e) means for producing a first signal corresponding to said error signal;
(f) means for producing a second signal corresponding to the dc component of said error signal, said second signal tracking said first signal to a point corresponding to a predetermined phase relationship;
(g) differential amplifier means for determining a difference between said first signal and said second signal; and (h) light emitting diode means for indicating when said first signal exceeds said second signal.
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations on said structural member upon activation by an alternating current input signal, said receiver film producing an alternating current output signal upon vibration of said structural member;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle differential between said alternating input signal and said alternating current output signal, said phase comparator means generating a signal proportional to said phase angle differential;
(d) low pass filter means for passing an error signal proportional to the signal generated by said phase comparator, said signal proportionally adjusting the frequency of said voltage controlled oscillator to a frequency within a preselected frequency range;
(e) means for producing a first signal corresponding to said error signal;
(f) means for producing a second signal corresponding to the dc component of said error signal, said second signal tracking said first signal to a point corresponding to a predetermined phase relationship;
(g) differential amplifier means for determining a difference between said first signal and said second signal; and (h) light emitting diode means for indicating when said first signal exceeds said second signal.
8. Apparatus for sensing a change in pressure on a structural member comprising:
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations in said structural member upon activation by an alternating current input signal, said receiver film producing alternating output signals in response to the vibration of said structural member, said frequency of vibration increasing when said structural member is deflected;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle of the signal produced by said receiver film with the phase of said alternating input signal;
(d) low pass filter means connected to the output of said phase comparator means for inputting a dc error signal to said voltage controlled oscillator means, said dc error signal forcing the frequency of said voltage controlled oscillator means toward said output signal so as to maintain a predetermined phase relationship between said output and input signals;
(e) means for producing a first signal corresponding to said error signal;
(f) means for producing a second signal corresponding to the dc component of said first signal, said second signal tracking said first signal to a point corresponding to said predetermined phase relationship;
(g) differential amplifier means for determining a difference between said first signal and said second signal;
(h) said differential amplifier means registering an output when said member is deflected;
(i) comparator means for registering a signal when said first signal exceeds said second signal; and (j) means for indicating when said first signal exceeds said second signal upon the deflection of said member.
(a) a structural member having a piezoelectric transmitter film and a piezoelectric receiver film adhered thereto, said transmitter film producing electro-mechanical vibrations in said structural member upon activation by an alternating current input signal, said receiver film producing alternating output signals in response to the vibration of said structural member, said frequency of vibration increasing when said structural member is deflected;
(b) voltage controlled oscillator means for generating said alternating input signal;
(c) phase comparator means for comparing the phase angle of the signal produced by said receiver film with the phase of said alternating input signal;
(d) low pass filter means connected to the output of said phase comparator means for inputting a dc error signal to said voltage controlled oscillator means, said dc error signal forcing the frequency of said voltage controlled oscillator means toward said output signal so as to maintain a predetermined phase relationship between said output and input signals;
(e) means for producing a first signal corresponding to said error signal;
(f) means for producing a second signal corresponding to the dc component of said first signal, said second signal tracking said first signal to a point corresponding to said predetermined phase relationship;
(g) differential amplifier means for determining a difference between said first signal and said second signal;
(h) said differential amplifier means registering an output when said member is deflected;
(i) comparator means for registering a signal when said first signal exceeds said second signal; and (j) means for indicating when said first signal exceeds said second signal upon the deflection of said member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US110,260 | 1987-10-20 | ||
| US07/110,260 US4841256A (en) | 1987-10-20 | 1987-10-20 | Piezoelectric phase locked loop circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1298381C true CA1298381C (en) | 1992-03-31 |
Family
ID=22332053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000580491A Expired - Lifetime CA1298381C (en) | 1987-10-20 | 1988-10-18 | Piezoelectric phase locked loop circuit |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US4841256A (en) |
| JP (1) | JPH021515A (en) |
| CA (1) | CA1298381C (en) |
| GB (1) | GB2211369B (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5028887A (en) * | 1989-08-31 | 1991-07-02 | Qualcomm, Inc. | Direct digital synthesizer driven phase lock loop frequency synthesizer with hard limiter |
| WO1993015850A1 (en) * | 1992-02-07 | 1993-08-19 | Valleylab, Inc. | Ultrasonic surgical apparatus |
| CH685648A5 (en) * | 1992-10-23 | 1995-08-31 | Kk Holding Ag | Multicomponent force and moment measuring arrangement. |
| JPH07128155A (en) * | 1993-09-13 | 1995-05-19 | Tokyo Electric Power Co Inc:The | Method and system for measurement of stress |
| US6053041A (en) * | 1995-02-27 | 2000-04-25 | The Regents Of The University Of California | Noninvasive method for determining the liquid level and density inside of a container |
| KR100352681B1 (en) * | 1995-03-16 | 2002-11-18 | 퀄컴 인코포레이티드 | Direct digital synthesizer driven pll prequency synthesizer with clean-up pll |
| US6032028A (en) * | 1996-04-12 | 2000-02-29 | Continentral Electronics Corporation | Radio transmitter apparatus and method |
| US5844491A (en) * | 1997-04-30 | 1998-12-01 | Endress + Hauser Gmbh + Co. | Apparatus for establishing and/or monitoring a predetermined filling level in a container |
| DE19742683C2 (en) * | 1997-09-26 | 1999-07-15 | Reich Kg Regel & Sicherheits | Method for determining the content of a gas cylinder |
| US5945854A (en) * | 1998-02-10 | 1999-08-31 | Ericsson Inc. | Phase locked loops including input amplitude control |
| DE10242970A1 (en) * | 2002-09-17 | 2004-04-01 | Vega Grieshaber Kg | Vibration level sensor compares mechanical oscillator amplitude and/or frequency with value and detects fault in mechanical oscillator if amplitude and/or frequency of value differs in defined manner |
| US6929343B2 (en) * | 2003-04-28 | 2005-08-16 | Hewlett-Packard Development Company, L.P. | Fluid detection system |
| US6874861B2 (en) * | 2003-04-29 | 2005-04-05 | Hewlett-Packard Development Company, L.P. | Printing device having a printing fluid detection system |
| US7029082B2 (en) * | 2003-07-02 | 2006-04-18 | Hewlett-Packard Development Company, L.P. | Printing device having a printing fluid detector |
| US7185960B2 (en) * | 2003-07-30 | 2007-03-06 | Hewlett-Packard Development Company, L.P. | Printing device having a printing fluid detector |
| US7950261B2 (en) | 2003-09-05 | 2011-05-31 | Yutaka Giken Co., Ltd. | Method and apparatus for press forming sheet material |
| DE102007059977B4 (en) * | 2006-12-12 | 2011-03-31 | Concentris Gmbh | Device for operating a micromechanical cantilever and measuring arrangement with such a cantilever |
| DE102009047728B4 (en) * | 2009-12-09 | 2012-08-09 | Endress + Hauser Gmbh + Co. Kg | Apparatus and method for determining at least two process variables of a liquid and / or gaseous medium in a container |
| RU2646541C2 (en) | 2013-04-23 | 2018-03-05 | Майкро Моушн, Инк. | Method of generating a drive signal for a vibratory sensor |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4056761A (en) * | 1975-09-11 | 1977-11-01 | Quintron, Inc. | Sonic transducer and drive circuit |
| US4395651A (en) * | 1981-04-10 | 1983-07-26 | Yujiro Yamamoto | Low energy relay using piezoelectric bender elements |
| US4538139A (en) * | 1982-04-30 | 1985-08-27 | Bolt Beranek And Newman Inc. | Signalling apparatus |
| US4473859A (en) * | 1982-09-22 | 1984-09-25 | Piezo Electric Products, Inc. | Piezoelectric circuit breaker |
| US4450375A (en) * | 1982-11-12 | 1984-05-22 | Kiwi Coders Corporation | Piezoelectric fluid control device |
| US4499394A (en) * | 1983-10-21 | 1985-02-12 | Koal Jan G | Polymer piezoelectric sensor of animal foot pressure |
| US4595855A (en) * | 1984-12-21 | 1986-06-17 | General Electric Company | Synchronously operable electrical current switching apparatus |
| GB2183371B (en) * | 1985-10-09 | 1989-09-27 | Canon Kk | Vibration wave motor and drive circuit therefor |
-
1987
- 1987-10-20 US US07/110,260 patent/US4841256A/en not_active Expired - Fee Related
-
1988
- 1988-10-18 CA CA000580491A patent/CA1298381C/en not_active Expired - Lifetime
- 1988-10-20 JP JP63263026A patent/JPH021515A/en active Pending
- 1988-10-20 GB GB8824535A patent/GB2211369B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB8824535D0 (en) | 1988-11-23 |
| US4841256A (en) | 1989-06-20 |
| GB2211369B (en) | 1992-02-12 |
| JPH021515A (en) | 1990-01-05 |
| GB2211369A (en) | 1989-06-28 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1298381C (en) | Piezoelectric phase locked loop circuit | |
| US5113116A (en) | Circuit arrangement for accurately and effectively driving an ultrasonic transducer | |
| EP0404023B1 (en) | Control apparatus for vibration driven motor | |
| US4277758A (en) | Ultrasonic wave generating apparatus with voltage-controlled filter | |
| US5130619A (en) | Drive control apparatus for an ultrasonic motor | |
| JP2912791B2 (en) | High frequency receiver | |
| WO1997026512A1 (en) | Apparatus and method for level sensing in a container | |
| US3985952A (en) | Elasto-optic device for spot wobble in a video disc player | |
| KR910005255A (en) | Magnetic head positioning device | |
| US3965440A (en) | Tunable laser oscillator | |
| US6938483B1 (en) | Phase-locked mechanical resonator pair and its application in micromachined vibration gyroscope | |
| US4578650A (en) | Resonance drive oscillator circuit | |
| US5774555A (en) | Switched capacitor bandpass filter for detecting pilot signal | |
| US6791421B2 (en) | Input-switching voltage-controlled oscillator and PLL-controlled oscillator | |
| CA2288121C (en) | Resonator having a selection circuit for selecting a resonance mode | |
| US2404026A (en) | Method of and system for translating signals | |
| US6374671B1 (en) | Method of stimulating an oscillator control for capacitive measurement of strength, acceleration and/or rotation speed | |
| CN1082275C (en) | An apparatus and method for using negative FM feedback in high quality oscillator devices | |
| US4388598A (en) | Loss-of-phase-lock indicator circuit | |
| JPH02245275A (en) | Device for driving ultrasonic vibrator | |
| US5159293A (en) | Voltage-controlled oscillator with wide modulation bandwidth | |
| JP3712141B2 (en) | Phase-locked loop device | |
| JP2008151632A (en) | Acceleration detector | |
| US5770975A (en) | Phase-locked loop circuit having a high-speed forcible pulling-in function | |
| RU2024911C1 (en) | Control unit of electromagnetic vibrator |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |