CN1818683A - Circuit and method for inspecting piezoelectric resonance mode by time-domain transient current - Google Patents

Abstract

A circuit utilizing time-domain transient current to detect piezoelectric resonant mode consists of digital-controllable voltage source, current-limiting resistance R1 and heavy-duty capacity C. It is featured as connecting N-MOSFET switch between said R1 and said C, also connecting resistance R3 and driving chip to N-MOSFET switch, connecting one end of driving chip to triggering signal, connecting resistance R2 to digital oscilloscope through resistance R4 and setting piezoelectric vibrator between resistance R2and R3.Its detecting method is also disclose.

Description

Adopt time-domain transient current to detect the circuit and the method thereof of piezoelectric resonance mode

Technical field

The invention belongs to the material and the components and parts technical field that are used for the detection of piezoelectric vibrator resonance, relate to the method and the circuit of the detection of the different modes of resonance of piezoelectric vibrator, particularly a kind of method and circuit thereof that adopts time-domain transient current to detect piezoelectric resonance mode.

Technical background

Piezoelectric crystal is a class important electron functional material, also is one of emphasis basic material in the message area.Piezoelectric crystal is the product of information science and two subject crossing of material science, has become the material foundation of a plurality of new discipline development in the message area.All kinds of electron devices made from piezoelectric crystal have the functions such as collection, transmission, conversion, processing, demonstration, execution and antagonism to information.Now piezoelectric crystal has become one of frontier development of material science, also is one of the key of development China modern high technology and core content.From P. Curie in 1880 and J. Curie brother at natural quartz (α β-SiO ₂) after crystal (piezoelectric quartz) go up to find piezoelectric effect, the piezoelectric crystal of having studied and having measured had reached nearly thousand kinds.Ferroelectric crystal has been obtained significant progress in recent years as an important branch of piezoelectric crystal.Succeeding in developing of lead magnesio-niobate lead titanates (PMNT) and lead lead-titanate niobium-zincate (PZNT) ferro-electricity single crystal caused the upsurge of the whole world about the relaxor ferroelectric monocrystal growth.

One of most important purposes of piezoelectric crystal is the piezoelectric vibrator (piezoelectricity crystal oscillator) that utilizes its piezoelectricity to make, and can be used for purposes such as resonator, wave filter.Spectral method in frequency domain point by point scanning is adopted in the detection of the piezoelectric resonator of piezoelectric vibrator always, this method requires the testing apparatus of complex and expensive, as Hewlett-Packard Corporation's (being present Agilent company) corresponding impedance spectrum instrument is arranged, but cost an arm and a leg, testing efficiency is lower.

Summary of the invention

Problem at the existence of piezoelectric vibrator detection range, the purpose of this invention is to provide a kind of circuit and method thereof that time-domain transient current detects piezoelectric resonance mode that detect that adopt, this testing circuit and method thereof are simple, with low cost, can be used for the detection of piezoelectric vibrator, also can be used for intuitively observing simultaneously the Unsteady State Response of piezoelectric device.

Design of the present invention is to excite simultaneously by the different modes of resonance of step electric field to same piezoelectric vibrator, gather transient state charge and discharge electric current with time domain approach, adopt Fourier transform that this transient current is analyzed, thereby reach the resonance frequency of the different piezoelectric resonance mode correspondences of piezoelectric vibrator and the purpose of piezoelectric parameter detection thereof.

Theoretical foundation of the present invention is:

1) adopt the step electric field that the different modes of resonance of same piezoelectric vibrator are excited simultaneously, the sine wave under the observation different frequency is to the piezoelectric current that inspires of the different piezoelectricity patterns of piezoelectric vibrator; Because exciting is that individual pulse causes, therefore the expression formula of single resonance current is:

I(t)＝Aexp(-t/τ)×sin(2πft+phi) (1)

In the formula, ω equals 2 π f, different is that electric current is made up of a plurality of resonance currents when adopting the step pulse electric field to excite, so the linearity that its unified expression formula is such resonance current is sued for peace, consider the existence of displacement current simultaneously, then total electric current should comprise displacement current and two parts of resonance current:

$I\left(t\right)=A_0\exp (-t/{\mathrm{\τ}}_0)+\stackrel{k}{\mathrm{\Σ}}{A}_n\exp (-t/{\mathrm{\τ}}_n)\×\sin (2{\mathrm{\πf}}_{n}t+\mathrm{ph}{i}_n)...\left(2\right)$

The wherein very fast and not vibration of first decay, so its influence to test can ignore is carried out Fourier to the time domain electric current that obtains then and is changed and obtain its frequency, so just can obtain the resonance frequency under the different mode.

The present invention excites simultaneously by the different modes of resonance of step electric field to same piezoelectric vibrator, gather transient state charge and discharge electric current with time domain approach, adopt Fourier transform that this transient current is analyzed, can draw resonance frequency and other piezoelectric parameter of different piezoelectric resonance mode correspondences, it is simple to have metering circuit, advantage with low cost can intuitively be observed the Unsteady State Response of piezoelectric device simultaneously.Adopt the method for mentioning among the present invention, can design the driving circuit that piezoelectric vibrator is excited based on step or square-wave pulse.

This technological means of domain test by corresponding mathematical analysis and circuit design, had realized this process, and has obtained expected effect when characteristics of the present invention were to have proposed theoretically to piezoelectric vibrator.

The technical solution that realizes the foregoing invention purpose is: a kind of circuit that adopts time-domain transient current to detect piezoelectric resonance mode, it is characterized in that, this circuit comprises: a digital controllable voltage source, on this digital controllable voltage source, be connected with current-limiting resistance R1, current-limiting resistance R1 links to each other with large bulk capacitance C, be connected with the N-MOSFET switch between resistance R 1 and the large bulk capacitance C, also be connected with chip for driving IR2110, resistance R 3 on the N-MOSFET switch, the end of chip for driving IR2110 links to each other with trigger pip; One end of resistance R 3 links to each other with large bulk capacitance C, resistance R 2, and resistance R 2 links to each other with digital oscilloscope by resistance R 4, and the piezoelectric vibrator measuring junction is arranged between resistance R 2 and the R3.

Foregoing circuit detects the method that time-domain transient current detects piezoelectric resonance mode, it is characterized in that the concrete operations step is as follows:

The first step: the piezoelectric vibrator that will polarize places the relevant position of test circuit, and polarised direction is with to apply direction of an electric field consistent;

Second step: open the digital controllable power supply and charge, till voltage is stable, open digital oscilloscope simultaneously to capacitor C;

The 3rd step: give a high trigger signal, make the N-MOSFET switch conduction, make the step electric field be applied to the piezoelectric vibrator two ends by chip for driving IR2110;

The 4th step: obtain transient current information by oscillograph with piezoelectric resonator circuit;

The 5th step: obtain frequency domain information in the time domain electric current by Fourier transform, obtain corresponding resonance frequency.

There are being long history and rich experience in Xi'an Communications University's electronic material and key lab of the device Ministry of Education aspect piezoelectricity ferro material and the device.The present invention is one of technological achievement of finishing in implementing the Department of Science and Technology great basic research project 973 material fields " some underlying issues research sub-project-ferroelectric ceramics dielectric, nonlinears of informational function pottery and adjustable mechanism research " and project of national nature science fund project " electric field is to the research of ferroelectric microcell modulating action " process of Xi'an Communications University's electronic material and key lab of the device Ministry of Education.

Description of drawings

Fig. 1 is that the present invention detects the circuit theory diagrams that time-domain transient current detects piezoelectric resonance mode.

Fig. 2 is the PZT piezoelectric ceramics oscillator synoptic diagram of four kinds of different sizes among the present invention.

Fig. 3 is the transient current curve under the strip sheet vibration mode.

Transient current curve under Fig. 4 side of being sheet shear mode.

Fig. 5 is the transient current curve under the disk vibration mode.

Fig. 6 is the transient current curve under the long excellent vibration mode.

Fig. 7 is the transient current curve of PMNT monocrystalline.

Fig. 8 is a PMNT monocrystalline transient current fourier transform spectrum.

Fig. 9 is a PMNT monocrystalline impedance frequency spectrum.

Figure 10 is application example figure of the present invention.

Wherein:

R1 is a current-limiting resistance among Fig. 1, and R2 is a sampling resistor, and R3 is a discharge loop resistance, and R4 is an impedance matching resistance, and digital oscilloscope is the digital oscilloscope of Tek company.C is a large value capacitor.The high-voltage high-speed switch is N-MOSFET, and IR2110 is a corresponding M OSFET switch drive chip.In the time of test high pressure is added to the capacitor two ends, gives trigger pip of IR2110 chip by the trigger pip trigger pip then, open high-voltage high-speed switch N-MOSFET, voltage just can be added to the two ends of sample in the very short time like this.The step pulse rising edge time like this is less than 50ns.Observe its current waveform by oscillograph, just can obtain data with the piezoelectric resonator correlated current.

Fig. 2 is the piezoelectric vibrator synoptic diagram of four kinds of different sizes.Wherein (a) is the strip sheet vibration mode, thick 25mm, 5mm and the 1mm of being respectively of these strip sheet size length and width; (b) side's of being sheet shear mode, this side's chip size are that length and width 5mm thickness is 1mm; (c) be the disk vibration mode, this disk diameter is 0.5mm for 10mm thickness; (d) be long excellent vibration mode, the excellent oscillator of this length is of a size of 1mm * 1mm * 5m.

Fig. 3 is the transient current curve under the strip sheet vibration mode.Wherein (a) is 10 μ s; (b) be 20 μ s; (c) be 100 μ s; (d) be 200 μ s;

Transient current curve under Fig. 4 side of being sheet shear mode.Wherein (a) is 20 μ s; (b) be 50 μ s;

Fig. 5 is the transient current curve under the disk vibration mode.Wherein (a) is 10 μ s; (b) be 20 μ s;

Fig. 6 is the transient current curve under the long excellent vibration mode.Wherein (a) is 20 μ s; (b) be 50 μ s; (c) be 100 μ s; (d) be 200 μ s;

Fig. 7 is the transient current curve of PMNT monocrystalline.

Fig. 8 is a PMNT monocrystalline transient current fourier transform spectrum.

Fig. 9 is a PMNT monocrystalline impedance frequency spectrum.

Figure 10 is the result that the present invention tests different piezoelectrics.Wherein (a) is to PMNT ferro-electricity single crystal detected piezoelectric resonator electric current under different electric field intensity; (b) be to PMNT ferroelectric ceramics detected piezoelectric resonator electric current under different electric field intensity; (c) be PZT pottery detected piezoelectric resonator electric current under different electric field intensity to modification; (d) be to lead magnesio-niobate (PMN) ferroelectric ceramics detected transient current that does not have piezoelectric resonator under different electric field intensity.

The present invention is described in further detail below in conjunction with embodiment that accompanying drawing and inventor provide.

Embodiment

According to the Fourier transform theory, a square-wave pulse equivalence is the linear combination of a series of sine wave.The lower frequency limit of the sine wave that these are a series of is by the inverse of the width that equals this square wave, and sinusoidal wave upper limiting frequency equals the inverse of this square wave rising edge time.If be ideal sine wave, the rising edge time is 0 second, and then Dui Ying upper limiting frequency is infinitely great.And a step pulse can be thought a square wave with unlimited width.This step pulse just is equivalent to adopt this lower frequency limit to be infinitesimal.The set of the sine wave that frequency coverage is very wide when adopting a step pulse that piezoelectric vibrator is excited like this excites this piezoelectric vibrator.When the test frequency of outside equaled the intrinsic resonance frequency of piezoelectric vibrator, this mode of resonance will be for exciting.In the appearance that shows as the unusual of an impedance on the impedance spectrum and be attended by a phase anomaly peak on the loss frequency.If detect its electric current in time domain, W.C.Cady calculated the time domain piezoelectric current under such a-c cycle driving.And obtained the expression-form shown in (1) formula:

I(t)＝I ₀sin(ωt+phi) (1)

I in the following formula ₀Be its resonance current amplitude, ω is its vibration frequency, and phi is a phase place.Just can draw the resonance frequency of this piezoelectric vibrator like this when the frequency of observing resonance current.

Equally when adopting step pulse that piezoelectric vibrator is excited, can observe sine wave under the different frequency to the piezoelectric current that inspires of piezoelectric vibrator difference piezoelectricity patterns.Because exciting is that individual pulse causes, therefore can calculate the expression formula position of single resonance current:

I(t)＝Aexp(-t/τ)×sin(2πft+phi) (2)

Here ω equals 2 π f.Different is that electric current is made up of a plurality of resonance currents when adopting the step pulse electric field to excite.Therefore its unified expression formula should be the linearity summation of such resonance current, considers the existence of displacement current simultaneously, and then total electric current should comprise displacement current and two parts of resonance current:

$I\left(t\right)=A_0\exp (-t/{\mathrm{\τ}}_0)+\stackrel{k}{\mathrm{\Σ}}{A}_n\exp (-t/{\mathrm{\τ}}_n)\×\sin (2{\mathrm{\πf}}_{n}t+{\mathrm{phi}}_n)...\left(3\right)$

The wherein very fast and not vibration of first's decay, so its influence to test can be ignored.Then the time domain electric current that obtains is carried out the Fourier variation and obtain its frequency, so just can obtain the resonance frequency under the different mode.

Fig. 1 detects the circuit theory diagrams that time-domain transient current detects piezoelectric resonance mode.Circuit comprises: a digital controllable voltage source, on this digital controllable voltage source, be connected with a current-limiting resistance R1, current-limiting resistance R1 links to each other with a large bulk capacitance C, be connected with the N-MOSFET switch between a resistance R 1 and the large bulk capacitance C, also be connected with chip for driving IR2110, resistance R 3 on the N-MOSFET switch, the end of chip for driving IR2110 links to each other with trigger pip, one end of resistance R 3 links to each other with large bulk capacitance C, resistance R 2, resistance R 2 links to each other with digital oscilloscope by resistance R 4, and the piezoelectric vibrator measuring junction is arranged between resistance R 2 and the R3.

The principle of work of this circuit is:

When the N-MOSFET switch turn-offed, this digital controllable voltage source was to large bulk capacitance C charging, and capacitor C is discharged to piezoelectric vibrator in the time of the N-MOSFET switch conduction;

Capacitor C, the N-MOSFET switch, piezoelectric vibrator and sampling resistor R2 constitute discharge loop; Chip for driving IR2110 cooperates the N-MOSFET switch to use, and input signal arrives the N-MOSFET switch by this chip for driving IR2110, directly controls conducting and shutoff;

Digital oscilloscope links to each other with resistance R 2 by the resistance R 4 of coupling, is used to obtain the change in voltage of 2 two sections of resistance R, obtains to flow through the current information of piezoelectric vibrator itself; When the N-MOSFET switch is closed once again, piezoelectric vibrator is by resistance R 3 discharges.

Step pulse can be added to the two ends of sample by this circuit.The rising edge time of general this step pulse is limited to 20MHz less than 50 nanoseconds on its spectral range.

The vibration principle of piezoelectric vibrator is exactly an electromechanical Coupling of utilizing piezoelectrics.At first make electric energy be converted to mechanical energy, and then mechanical energy is converted into electric energy by piezoelectric effect by inverse piezoelectric effect.The reciprocal process of one-period has just constituted the periodic vibration of piezoelectric vibrator like this.By the effect of different electromechanical coupling factors, can obtain the vibration of piezoelectric vibrator different mode.Therefore also can classify to vibration mode by electromechanical coupling factor is classified to come.Common electromechanical coupling factor has: k ₃₁, k ₃₃, k ₁₅, k _p, k _tThe vibration mode of their correspondences is respectively like this:

1) electric field is perpendicular to the telescopic pattern (k of length ₃₁);

2) electric field is parallel to the telescopic pattern (k of length ₃₃);

3) electric field is parallel to the thickness shearing mode (k of direction of wave travel ₁₅);

4) radial vibration mode (k of thin discs _p);

5) electric field is parallel to the flexible pattern (k of thickness of direction of wave travel _t).

The vibration mode of these five kinds of piezoelectric vibrators just can be excited out under the effect of suitable external AC field.Excite the vibration of these five kinds of different modes, the size of piezoelectric vibrator has requirement.Such as, if excite the length vibration mode of strip sheet, generally require the length l of strip sheet will be much larger than its width w and thickness t.If excite the thickness vibration mode of circle sheet, require its diameter d will be much larger than its thickness t.Also there are a plurality of modes of resonance simultaneously in certain same piezoelectric vibrator, have thickness resonance and resonance radially simultaneously as a thin discs, and a strip sheet exists length resonance, width resonance and thickness resonance.Author designed has been made the piezoelectric vibrator of the ceramic different size of lead zirconate titanate (PZT) for this reason, and in the hope of inspiring the vibration mode that will observe, the size of this sample as shown in Figure 2.

Foregoing circuit detects the method that time-domain transient current detects piezoelectric resonance mode, and concrete steps are as follows:

First: the piezoelectric vibrator that will polarize places the corresponding position of test macro, and polarised direction is with to apply direction of an electric field consistent.

Second: open the digital controllable power supply and charge, till voltage is stable to capacitor C.Open digital oscilloscope simultaneously.

The the 3rd: give a high trigger signal, make the N-MOSFET switch conduction by chip for driving.The step electric field is applied on the piezoelectric vibrator.

The the 4th: obtain transient current information by oscillograph with piezoelectric resonator circuit.

The the 5th: obtain frequency domain information in the time domain electric current by Fourier transform, obtain corresponding resonance frequency.

Fig. 3 to Fig. 6 adopts circuit of the present invention that the different piezoelectricity patterns of the piezoelectric vibrator under the different mode are excited the transient current curve that obtains.The circuit curve of different vibration frequencies as we can see from the figure, this vibration mode with expection matches.That is to say that the circuit that adopts among the present invention can excite five kinds of the most frequently used piezoelectric resonance modes.

Fig. 7 excites the transient current curve that obtains to PMNT monocrystalline side sheet piezoelectric vibrator.Fig. 8 makes the frequency that obtains behind the Fourier transform to Fig. 7 (b) transient current, with Fig. 9 adopt the point by point scanning spectral method to data compare coincide fine.This has also just proved the feasibility of the present invention in concrete the application.

It below is the specific embodiment that the inventor provides.

Embodiment 1: adopt the present invention that other piezoelectric is detected.

Chosen the PZT pottery in this example, the PMN-32PT pottery, PMN-32PT monocrystalline and PMN pottery are as tested object.Sample is little side's sheet or sequin, and therefore possible piezoelectric vibration pattern is the flexible pattern of planar radial stretching vibration pattern and thickness.That is to say the oscillating current that on transient current spectrum, should only may observe two frequencies.And the PMN pottery does not have piezoelectricity, therefore should not observe resonance current.Transient current has proved this point among Figure 10.To the PZT pottery, the data that the data about resonance frequency that PMN-32PT pottery, the transient current of PMN-32PT monocrystalline do to obtain behind the Fourier transform also obtain with the spectrum scan mode therewith match simultaneously.

Claims (2)

1. circuit that adopts time-domain transient current to detect piezoelectric resonance mode, it is characterized in that, this circuit comprises: a digital controllable voltage source, on this digital controllable voltage source, be connected with current-limiting resistance R1, current-limiting resistance R1 links to each other with large bulk capacitance C, be connected with the N-MOSFET switch between resistance R 1 and the large bulk capacitance C, also be connected with chip for driving IR2110, resistance R 3 on the N-MOSFET switch, the end of chip for driving IR2110 links to each other with trigger pip; One end of resistance R 3 links to each other with large bulk capacitance C, resistance R 2, and resistance R 2 links to each other with digital oscilloscope by resistance R 4, and the piezoelectric vibrator measuring junction is arranged between resistance R 2 and the R3.

2. one kind is detected the method that time-domain transient current detects piezoelectric resonance mode, it is characterized in that, this method adopts the described circuit of claim 1, and concrete steps are as follows:

The first step: the piezoelectric vibrator that will polarize places the corresponding position of test macro, and polarised direction is with to apply direction of an electric field consistent;

Second step: open the digital controllable power supply and charge, till voltage is stable, open digital oscilloscope simultaneously to capacitor C;

The 3rd step: give a high trigger signal, make the N-MOSFET switch conduction, make the step electric field be applied to the piezoelectric vibrator two ends by chip for driving IR2110;

The 4th step: obtain transient current information by oscillograph with piezoelectric resonator circuit;

The 5th step: obtain frequency domain information in the time domain electric current by Fourier transform, obtain corresponding resonance frequency.

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