CN1182403C - Piezoelectric ceramics transducer admittance circular graphic instruments - Google Patents

Abstract

The present invention relates to a device used for admittance circle measurement of a piezoelectric ceramic transducer in the acoustics field of physics, which is a device used for generating and receiving sound in the acoustics field. An admittance circle needs measuring to obtain main parameters before the piezoelectric ceramic transducer is used, and then the application of the piezoelectric ceramic transducer can be guided. The present invention is an integral technical scheme which aims at the admittance circle measurement of the piezoelectric ceramic transducer and combines hardware and software analysis of a PC. The scheme has the characteristics of high precision, low cost, convenient operation and strong pertinency. The hardware part mainly completes the function of data acquisition of the admittance circle, and the software part mainly completes the data analysis function. Communication between the hardware part and the software part is completed through a serial port of a computer. The hardware part is mainly composed of a signal generation circuit, a calculation and acquisition circuit and a data communication circuit, and the software part is mainly composed of a data communication part, a user interface part and a data processing part.

Description

Piezoelectric ceramic transducer admittance circle diagram instrument

Technical field

The present invention is a kind of device that relates to field of acoustics in the physics, relevant piezoelectric ceramic transducer admittance measurement.

Piezoelectric ceramic transducer is that field of acoustics is used to produce and a crystalloid material of reception sound.Needed to know that its major parameter just can practice before using piezoelectric ceramic transducer, its parameter mainly comprises: resonance point frequency, static capacity (C0), motional impedance (R1, C1, L1), electromechanical coupling factor, equivalent frequency range, Qm Q, temperature stability etc.If can measure the admittance value near the band frequency scope resonance point of piezoelectric ceramic transducer, just can analyze and extract above required parameter.Because the admittance value in this band frequency scope forms an approximate circle on the admittance complex coordinates, so be referred to as admittance circle.

Piezoelectric ceramic transducer admittance circle diagram instrument is to be used for the admittance characteristic of piezoelectric ceramic transducer is analyzed, thereby obtains the instrument of its main parameter.It is mainly used in detection and the use of instructing piezoelectric ceramic transducer, be to piezoelectric ceramic transducer effectively measure, the comprehensive solution of analysis or qualified/defective test.

Background technology

Piezoelectric ceramics can extend under the effect of alternating voltage a little while, shortens a little while, produces vibration, thereby sounds, and this phenomenon is piezoelectric effect on physics, and the pottery with such effect also just is piezoelectric ceramics.On the contrary, when it when being subjected to mechanical pressure, must be little as acoustic vibration even this pressure is small, the capital produces change of shape such as compression or elongation, along with the variation of shape, the two sides of this crystal can produce different electric charges, like this, when acoustic wave action was on piezoelectric ceramics, electric charge will become electric signal.The piezoelectric ceramic transducer that constitutes with piezoelectric ceramics has become one of effective means of generation and reception sound.

Admittance circle about piezoelectric ceramic transducer detects generally by two kinds of methods at present, and the one, adopt the admittance circle detection of making piezoelectric ceramic transducer from U.S.'s import, general electric impedance analyzer.Agilent4192A (being HP4192A originally) for example, but its price is very expensive, greatly about 2-3 is ten thousand dollars, domesticly has the few of this instrument.And it is not connected with PC, the interface that needs own exploitation and computing machine with and the program that is specifically designed to piezoelectric ceramic transducer, be used for to the parameter of transducer analyze, extraction, printout.The application surface of Agilent4192A wide (admittance of making piezoelectric ceramic transducer detects the Just One Of Those Things partial function), so its performance index are also very high, cause the pick-up unit complexity, cost is very high, and the parameter analysis of making piezoelectric ceramic transducer is extracted also inconvenient.

Another method is to adopt general waveform generator to carry out point by point scanning, and uses the oscillograph recording reading, and its admittance circle is depicted, and obtains the parameter of piezoelectric ceramic transducer then, and the method not only wastes time and energy, and precision is not high.

The development of microelectric technique, the signal source that makes the acquisition frequency accurately to control becomes possibility.Along with the popularization and application of PC, developing application on PC combines hardware and software, develops a kind of cost instrument relatively low, that be specifically designed to piezoelectric ceramic transducer admittance circle mensuration, just can solve above contradiction.

Summary of the invention

A kind of device that is used for measuring the piezoelectric ceramic transducer admittance circle diagram, wherein hardware and PC software are combined, finish piezoelectric ceramic transducer admittance data acquisition function by hardware components, finish drawing and data analysis function by software section, two parts are by computing machine serial port mutual communication, be characterised in that: adopt piezoelectric ceramic transducer is connected with variable resistor, obtain current value on the piezoelectric ceramic transducer by the magnitude of voltage on the variable resistor, record electric current and voltage by piezoelectric ceramic transducer and obtain impedance under the current frequency, resistance value is got the admittance value that just obtains under the current frequency reciprocal;

Have in the metering circuit:

1). signal generating circuit, adopt Direct Digital frequency synthesis technology to obtain sinusoidal signal, 89C51 does frequency control with single chip computer AT, signal is amplified the sinusoidal signal of acquisition with power operational amplifier;

2). computing and data acquisition circuit comprise peak-detector circuit and phase detecting circuit, peak-detector circuit comprises a high speed operation amplifier, a low speed operational amplifier and two fast recovery diodes, is used to detect the crest voltage of the sinusoidal signal of dynamic change; Phase detecting circuit adopts analog multiplier, is used to detect the phase difference value of two-way sine wave;

3). telecommunication circuit, as the communication slave computer, computing machine sends instruction by computer software to slave computer as the communication host computer with single-chip microcomputer, after the slave computer execution command, the data that collect is sent to host computer;

The data that the software processes of using employing Microsoft Visual C++6.0 to write on computers collects, obtain the admittance data of piezoelectric ceramic transducer, on computer display, make admittance circle diagram, thereby piezoelectric ceramic transducer is carried out the parameter extraction of specificity analysis and piezoelectric ceramic transducer.

This programme can be realized low cost, high precision, the requirement efficiently of use aspect.

Content of the present invention is divided into ultimate principle, software design, three parts of hardware design.

1. ultimate principle:

The sinusoidal voltage signal that frequency is accurately controlled, stable is added in the two ends of piezoelectric ceramic transducer, measure the electric current that flows through in the transducer branch road then, with voltage of signals divided by branch current, just can obtain its impedance under current frequency, at this moment impedance is a plural number, comprises real part and imaginary part.Resistance value is got inverse, just obtain the admittance value of transducer under current frequency.Measure its admittance value near one section continuous frequency range the piezoelectric ceramic transducer resonance point, just can on admittance complex coordinates (real part of admittance is a horizontal ordinate, and imaginary part is an ordinate), draw an approximate circle, be referred to as admittance circle.The symbol and the equivalent electrical circuit of piezoelectric transducer please refer to Fig. 1.

Because current value is not easy to detect, solution is resistance of series connection in branch road, because ohmically magnitude of voltage and current value are directly proportional, just can obtain the branch current value so detect ohmically magnitude of voltage.Because at the transducer of different purposes, the scope of its motional impedance R1 is very wide, from several ohm to several kilohms, so precision in order to guarantee to detect, the resistance value of being connected needs scalable, and is too big or too little to avoid ohmically voltage, so that be difficult to detect.Its schematic circuit as shown in Figure 2, wherein Us is that sinusoidal excitation signal, R are the internal resistance of source, R _MFor branch road resistance in series, L are piezoelectric ceramic transducer.The impedance Z of transducer is as shown in Figure 2:

$Z=\frac{u_A-u_B}{u_B/R_M}=R_M|\frac{u_A}{u_B}-1|$ (u _ABe branch road both end voltage, u _BBe resistance R _MBoth end voltage)

If: u _A=K _Ae ^Jwt, u _B=K _Be ^{J (ω t+ )}

Can get: $\frac{U_{\mathrm{AM}}}{U_{\mathrm{BM}}}=\frac{K_A}{K_B}$ (U _AMBe u _APeak value, U _BMBe u _BPeak value)

Then:

In the formula:

(R is a real part of impedance) 1)

(X is the imaginary part of impedance) 2)

The admittance Y of transducer is:

$Y=\frac{1}{Z}=\frac{R}{R^2+X^2}+j\frac{X}{R^2+X^2}=G+\mathrm{jB}$ (G is that real part, the B of admittance is the imaginary part of admittance)

By formula 1) and 2) as can be known, the admittance of transducer is a plural number, as long as measure the U under the different frequency _AM, U _BM, Cos numerical value, know R then _MSize just can obtain the admittance feature of transducer.

2. hardware design

Hardware components is by common nine kinds of needles serial port and compunication.Hardware is divided into three parts:

1) signal generating circuit: need to produce the sinusoidal signal that resolution is 1Hz in actual applications, the degree of stability of frequency is in 1Hz, and frequency band range is 1Hz～0.5MHz.Adopt analog form to be difficult to meet the demands, therefore adopt the mode of Direct Digital synthetic (DDS) to obtain sinusoidal signal.Be characterized in: frequency accuracy height, accurately control easily.To DDS chip transmission frequency control word, just can export the sine wave signal of corresponding frequencies.The function that the DDS family chip that U.S. Analog Device company releases such as AD7008, AD9850 all can realize the Direct Digital frequency synthesis.

Simply introducing structure and the performance of AD7008: AD7008 below is that Analog Device company adopts synthetic (DDS) technology of advanced Direct Digital, the high integration frequency synthesizer of release.Its inside comprise 32 phase accumulators, cosine/sine table, 10 DAC of high-performance, with serial and the parallel interface and the control circuit etc. of microcomputer, can realize the frequency synthesis of digital programming Control formula.Connect the precision interval clock source, AD7008 can produce sine waves of control able to programme of a frequency and phase place.When AD7008 worked under the crystal oscillator of 20MHz, its output frequency resolution rate can reach 0.047Hz, and maximum output frequency can reach 5MHz.

AD7008 interface control is fairly simple, can be with 8 or 16 bit parallel mouths or control datas such as the direct incoming frequency of single file mouth, phase place and amplitude modulation amplitude.Here adopt the SPI mouth of serial to be connected with AT89C51, referring to need be with the programming Control that just can realize on SDATA, the SCLK of AD7008, the delivery outlet that LOAD receives single-chip microcomputer the AD7008 output frequency.The phase accumulator value Δ Phase that AT89C51 needs only with 32 of serial mode inputs just can change frequency, and the relation of phase accumulator value and frequency is as follows:

$f=\frac{\mathrm{\ΔPhase}\×f_{\mathrm{CLOCK}}}{2^{32}}(0\≤\mathrm{\ΔPhase}\≤2^{32}).$ F wherein _CLOCKBe crystal oscillator frequency.

The sinusoidal signal of AD7008 output needs to amplify by amplifier, and fundamental purpose is in order to improve its load-carrying ability.When being used to measure the transducer of higher resistance, just passable with common amplifier, such as NE5534, NE5532, AD818 can.If relate to the more low-impedance transducer of measurement, just need to use the bigger amplifier of power, promptly can export the amplifier of big electric current, as LM3875, LM3886 of National Semiconductor company or the like.When using LM3875, LM3886, its closed loop enlargement factor must be greater than 10, and system can stablize.

Here can only can not avoid the amplifier overload by the method that increases the branch road resistance in series by the carrying load ability that strengthens amplifier, its principle is as follows: if resistance in series is strengthened, can avoid the amplifier overload, but under many circumstances, can cause the error measured very big, even the admittance situation of change when occurring detecting frequency change.

2) computing and data acquisition circuit:, therefore under the excitation of different sinusoidal signals, can present different admittance characteristics owing to contain electric capacity and inductance in the equivalent electrical circuit of piezoelectric ceramic transducer.In order to detect its admittance characteristic, the factor that embodies its admittance characteristic in the circuit need be converted to by computing circuit can detected voltage, obtains by the collection of A/D translation circuit then.Computing circuit is divided into two parts: peak detection circuit and phase detecting circuit.Peak detection circuit is used to detect the crest voltage of the sinusoidal signal of dynamic change.Phase detecting circuit is used to detect the phase difference value of two-way sine wave, and phase differential changes in-90 °～+ 90 ° scope, need be translated into the voltage of 0～5V.Convert to after the voltage, just can obtain by 12 A/D transducer collection.Computing circuit please refer to Fig. 3.

u _xWith u _yPhase differential detect with the high-precision analog multiplier.Analog multiplier is output as:

With two frequency multiplication item eliminations in the following formula, get final product with low-pass filter So

Can obtain

Because u _x, u _yPeak value U _XM, U _YMAvailable peak detector is tried to achieve (peak-detector circuit please refer to Fig. 4), just can obtain the cosine of phase differential according to following formula.

In the side circuit design, the MPY634 of integrated four-quadrant analog multiplier AD633, AD534, AD734 or the Texas Instrument company of employing U.S. Analog Device company all can realize asking the function of phase differential.

Peak-detector circuit needs to use two amplifiers as shown in Figure 4 in the circuit, first amplifier IC1 must be the high speed amplifier, require gain bandwidth product greater than 50M, voltage Slew Rate greater than 500V/ μ s.LM6171, the LM6161 of the AD818 of AnalogDevice company or National Semiconductor company all can meet the demands.Amplifier IC2 adopts the low speed amplifier to get final product, and the LF411 of common National Semiconductor company just can meet the demands.D1, D2 are fast recovery diode, can select 1N4148 or schottky diode for use.C2 and R2 determine the retention time of crest voltage, and C1 can get 0.1 μ F, and R2 can get 10M Ω.R1 can get 2K Ω, and C1 and R3 are used to adjust precision, can regulate its size according to side circuit.

The A/D transducer can be selected the TLC2543 of Texas Instrument company, perhaps the MAX147 of Maxim company.They are connected with processor by spi bus, can satisfy the data collection task in the native system preferably.The REF02 that TLC2543 can use MAXIM is as voltage-reference, and it is output as REF02+5V, and stable stability is 3ppm/ ℃.

3) telecommunication circuit: be responsible for and the communicating by letter of PC (host computer) by single-chip microcomputer (slave computer) in the circuit.Send instruction by computer software to slave computer, after the single-chip microcomputer execution command, the voltage that collects is sent to host computer.In the process of work, slave computer is given in the order of host computer transmission frequency, and slave computer control produces the correspondent frequency signal, simultaneously with under this frequency, be used for characterizing three road voltage collections of piezoelectric ceramic transducer admittance characteristic and feeding back to host computer.System adopts the AT89C51 of American ATMEL as slave computer, communicates by letter with host computer by the serial port of AT89C51.Because what the computing machine serial port was used is the RS232 level, AT89C51 then is the CMOS level, and intermediate demand is realized its level conversion function with the MAX232 of U.S. MAXIM company.MAX232 only needs+work of 5V single supply, and is easy to use.

The baud rate of slave computer and host computer must unanimity can be communicated by letter, because data volume is little, therefore adopts typical transmission rate 9600bps just passable.The baud rate of AT89C51 is set by its inner timer, and its external crystal-controlled oscillation frequency is used 11.0592MHz (9600 integral multiples), and register TH1=0xFD is set, and baud rate just can be set is 9600bps.

3. software design:

Software section of the present invention is write by Microsoft Visual C++6.0.On window2000 or higher version, move.Software can be divided into three parts by function:

1) data communication function: operator's order is sent to slave computer, simultaneously the data that feed back from slave computer acceptance.Order sends to slave computer by the serial port (COM1, COM2, COM3, COM4) of computing machine.In Visual C++, finish and the communicating by letter of slave computer by the Windows api function.Its main used function is described below:

CreateFile: open serial port SetCommState the serial ports baud rate is set

The buffer zone WriteFile that PurgeComm empties serial port sends data to slave computer

ReadFile receives data from slave computer.

Host computer and slave computer are with master-slave mode work, and host computer sends order, slave computer feedback data.The order of host computer transmission frequency, the ending of order is a sign with " H ", after slave computer receives " H ", fill order, promptly export the corresponding frequencies sinusoidal signal, wait for 0.5 second then after, the result who gathers the A/D conversion also sends to host computer, its result is the character string of 12 characters, is representing three magnitudes of voltage (magnitude of voltage represented in per four characters) respectively.All data are all with the transmission of the form of ASCII character, just send after promptly frequency and the equal step-by-step of voltage being converted to ASCII character.Therefore on host computer and slave computer, the subroutine of changing mutually between ASCII character and the binary code is arranged all.

2) user interface: the user can select the size of branch road resistance in series on software, and the initial frequency of scanning, the termination frequency of scanning, frequency step during scanning or the like.User interface also comprises graphical display window, the man-machine operation interface that data are preserved and graphic printing is exported, and the demonstration of measurement result or the like.User interface please refer to Fig. 5.

The user at first selects the computing machine serial slogan that is connected with equipment, clicks From initial frequency, termination frequency, the frequency step of keyboard input and output frequency sweeping, click again then

System promptly begins to scan, and with every speed of 0.6 second, on the G-B coordinate of on the left side, from initial point, draws the admittance circle of measured piezoelectric ceramic transducer in the direction of the clock.Make G-F figure and B-F figure simultaneously on the coordinate on the right.(G: admittance real part, unit are ms; B: the admittance imaginary part, unit is ms; F: frequency, unit is Hz).Can click " stopping " in the scanning process and stop scanning.Frequency values in the scanning process, phase differential, admittance real part, these data of admittance imaginary part all show on screen in real time, and are kept at simultaneously in class members's variable.

After the been scanned, the user can click any point that screen coordinate is fastened, and the coordinate figure of click place is read and shown to Automatic Program.

The parameter result that process analysis draws is presented at the upper right corner of screen.

3) data processing function: comprise mapping, data analysis, parameter extraction, printout, data preservation or the like function.In the process that detects, in real time data are shown on G-B coordinate and G-F, B-F coordinate, because the coordinate size can not change, so program can make normalized to the survey data, promptly chooses coordinate scale automatically according to the admittance value of surveying.

After all Data Detection finish, by optimizing algorithm the figure that is obtained is fitted to the circle of a rule, just can analyze the parameter of piezoelectric ceramic transducer then.After mapping finishes, software can be according to the theory of relevant piezoelectric ceramic transducer admittance circle, calculate the parameters of transducer, for example resonance point frequency, static capacity (C0), motional impedance (R1, C1, L1), electromechanical coupling factor, equivalent frequency range, Qm Q or the like.

Technical solutions according to the invention have a lot of advantages at the detection of piezoelectric ceramic transducer admittance circle: precision height, with strong points, use simple, quick; And the detection that notebook computer just can directly apply to industry spot is gone up in connection; The more important thing is that compare its cost with import instrument very cheap, have very big price advantage.

Description of drawings:

With reference to the accompanying drawings and explanation, can have more clearly the technical scheme among the present invention and characteristics thereof and advantage and understand.These accompanying drawings are:

Fig. 1 (a) is the symbol of piezoelectric ceramic transducer, and Fig. 1 (b) is near the lump equivalent electrical circuit piezoelectric ceramic transducer resonant frequency.C0 is a direct capacitance, and L1 is a dynamic inductance, and C1 is a dynamic capacity, and R1 is a dynamic resistance.

Fig. 2 is the basic principle schematic of testing circuit.R is the internal resistance of source, u _ABe sine signal source voltage, u _BBe branch road resistance in series voltage, R _MBe the branch road resistance in series, L is the piezoelectric ceramic transducer transducer, and Us is a sine signal source.

Fig. 3 is the signal computing circuit principle schematic.U wherein _ABe excitation power supply voltage, u _BBe branch road resistance in series voltage, R _MBe the branch road resistance in series; U _AMBe u _APeak value, U _BMBe u _BPeak value, Uxm is u _xPeak value, Uym is u _yPeak value; Ka, Kb, Km, Ko are scale-up factor; Uo is u _XyAmplify the magnitude of voltage after the low-pass filtering after Ko times.

Fig. 4 is the sinusoidal signal peak-detector circuit, is used to detect the positive peak voltage of sinusoidal signal.Wherein IC1, IC2 are operational amplifier.

Fig. 5 is the user interface of program, and the left side of interface upper part is user's operation part; The right of interface upper part is the parameter display part; The bottom at interface is the graphic presentation part.

Fig. 6 is the schematic diagram of circuit, and the detail of relevant circuit engineering scheme all embodies in the drawings.

Fig. 7 is the PCB figure (printed circuit diagram) of circuit, and the component symbol on the figure is consistent with the schematic diagram of Fig. 6.

Fig. 8 is according to the model machine of the technical program design admittance circle measurement result to a piezoelectric ceramic transducer.

Fig. 9 is import instrument HP4192A to the measurement result of the transducer of being surveyed among Fig. 8.

Embodiment:

Technical scheme according to above introduction has successfully designed model machine, and has obtained good effect in producing use.Its performance and technical indicator are as follows:

Frequency range 1Hz～0.5MHz

Frequency step 1Hz

Frequency accuracy ± 50ppm

Resonance frequency Measurement Resolution 1Hz

Motional impedance measuring error＜1%

Direct capacitance measuring error:＜2%

Qm measuring error:＜2%

The contrast of its performance and HP4192A please refer to Fig. 8 and Fig. 9.

The enforcement of scheme is divided into four parts: circuit theory diagrams, circuit PCB (printed circuit board (PCB)) figure, single-chip microcomputer (slave computer) program, PC (host computer) program.

1. circuit theory diagrams:

Schematic diagram please refer to Fig. 6, and IC1 is single chip computer AT 89C51, and IC2 is AD7008AP20.AT89C51 is by P0.0, P0.1, three mouth control of P0.2 AD7008 AP20.AD7008AP20 is a technical grade, and external crystal oscillator is 20MHz to the maximum, because crystal oscillator directly has influence on the precision of its output frequency, therefore wants service precision than higher crystal oscillator, preferably constant-temperature crystal oscillator.

The amplitude of the sinusoidal signal of AD7008 output is by R1, R2, three resistance decisions of R3, and the computing formula of its full amplitude output current is as follows:

${\mathrm{IOUT}}_{\mathrm{FULL}-\mathrm{SCALE}}=\frac{6233\×V_{\mathrm{REF}}}{R_3}$ V wherein _REF=1.27V (internal reference voltage)

When getting R _SEFWhen=390 Ω, R1=R2=39.9 Ω, the amplitude of its output signal is about 1V.After its output voltage amplified through amplifier difference (IC10/NE5534), its output voltage amplitude was 5V.Because the internal resistance of NE5534 is bigger, can not be used for the bigger output of power, and is more high-power if desired, need to use the power amplifier, for example LM3886 etc.

IC17 (NE5534), IC12 (LM6171), IC13 (LF411) are used to measure u _APeak value; IC18 (NE5534), IC14 (LM6171), IC15 (LF411) are used to measure u _B(u _A, u _BDefinition please refer to Fig. 2 or Fig. 3) peak value.R9, R34, R35 and switch SW 1, SW2 are used to regulate the size of transducer branch road resistance in series.IC17, IC18 are the forward amplifying circuit, IC17 enlargement factor Ka=1.5 wherein, IC18 enlargement factor Kb=2 (definition of Ka, Kb please refer to Fig. 3).

IC3 is four-quadrant analog multiplier AD633, and its output to the operational formula of input is:

$W=\frac{(X_1-X_2)(Y_1-Y_2)}{10V}+Z$

Here X ₂=Y ₂=Z=0, Km=1/10.IC16 (NE5534) is the forward amplifying circuit, its enlargement factor Ko=5 (definition of Km, Ko please refer to Fig. 3).Voltage after the amplification obtains DC component through after the low-pass filtering, adopts the RC filtering mode, and time constant is got 0.01 second (R=100 Ω, C=100 μ F).

According to Fig. 3, Uxm, Uym, Uo three part voltages are gathered into the impedance of transducer or Admittance Calculation formula following (wherein R10=3K, R11=2K) through A/D transducer TLC2543:

$\frac{U_{\mathrm{AM}}}{U_{\mathrm{BM}}}=\frac{U_{\mathrm{xm}}}{U_{\mathrm{ym}}}\·\frac{K_b}{K_a}\·\frac{R_{10}+R_{11}}{R_{11}}=\frac{U_{\mathrm{xm}}}{U_{\mathrm{ym}}}\·\frac{10}{3}$

With following formula

Be updated in following two formulas with Cos , just can obtain transducer real part of impedance and imaginary part under current frequency:

(R _MBe transducer branch road series impedance, R9, R34, R35 in the corresponding diagram 6)

R value and X value are updated in the following formula, just can obtain the real part G and the imaginary part B of transducer admittance under current frequency:

$Y=\frac{1}{Z}=\frac{R}{R^2+X^2}+j\frac{X}{R^2+X^3}=G+\mathrm{jB}$

Do conversion between RS-232 level and the CMOS level with MAX232 in the serial communication, serial communication only needs the nine needles serial port of three lines and PC just to be connected can carry out full-duplex communication, is respectively TXD, RXD, GND.

The power supply of circuit board is provided by transformer, because need the two-way power supply, positive voltage and negative voltage are provided respectively, therefore select for use and be with tapped pair of 15V transformer, become direct current behind the rectifier bridge heap of the output terminal of transformer through 1A600V, use the capacitor filtering of 1000 μ F/50V then, the voltage that comes out is again through just giving chip power supply after the three terminal regulator 7815,7915,7805.

Relate to analog amplify circuit in the system, its related resistors all needs to use precision resistance, can guarantee that just amplification multiple is accurately.Needing in the system has with the resistance of 0.1% precision: R5, R6, R7, R8, R9, R10, R11, R13, R14, R16, R17, R31, R32, R34, R35; Needing in the system has with the precision resistance of 0.5% precision: R1, R2, R3.

2. circuit printed circuit diagram (PCB figure):

PCB figure please refer to Fig. 7, and wherein Shen Se lines are top layer cabling (TopLayer), and the lines of light color are bottom cabling (BottomLayer).Chips all except AD7008 all adopt dual-in-line package.AD7008 is the PLCC44 encapsulation, for the ease of debugging, has adopted the PLCC socket.

PCB figure is divided into three parts, is power unit topmost, comprises three three terminal regulators and a rectifier bridge heap and relevant filter capacitor, and all three terminal regulators all need radiation fin.The left side below the power unit is the digital circuit part, the right is an artificial circuit part, the mode of digital simulation subregion wiring has been adopted in PCB figure design, wherein AD7008 and TLC2543 had both related to mimic channel, relate to digital circuit again, therefore place them in the intersection of simulation part and numerical portion, do like this and can reduce interference as much as possible.Because existing mimic channel in the circuit also has digital circuit,, need avoid the stack of digital loop and analog loopback for improving antijamming capability.

3. Single Chip Microcomputer (SCM) program:

AT89C51 uses 8051 kernels, and has expanded the FLASH memory under program on this basis.Program compiles with Franklin C51, and its master routine is as follows, and note please refer to program the right:

The register definitions header file * that #include " reg51.h "/* compiler provides/unsigned char recieve; Unsigned char buffer[8]; Unsigned char buffer_pointer=0; Char send_buffer[12]; Unsigned char send_buf_pointer=0; Unsigned long ad7008_reg; Header file */#include " ad.h "/* and relevant header file */#include " math.h " bit flag1=0 of TLC2543 operation that #include " delay.h " #include " ad70082.h "/* is relevant with the AD7008 operation; Unsigned long freq=0; Unsigned int ad_channel1; Unsigned int ad_channel2; Unsigned int ad_channel3; Sbit red_led=P0^5; Void delay_time (unsigned int n); / * time delay subroutine */void convert_char_to_freq (); / * will represent that the ASC II sign indicating number of frequency converts the subroutine * of binary number/void convert_ad_result_to_char () to; / * converts the binary result of AD conversion to subroutine */void main ()/* master routine */{ the int s of ASC II sign indicating number; Red_led=0; SCON=0x50; / * mode 1, allow to accept */＜!--SIPO＜DP n=" 10 "〉--〉＜dp n=" d10 "/TMOD=0x20; / * timer 1: timing mode, mode 2 (has the 8 bit timing device */TH1=0xFD that reinstall automatically; ET1=0; / * timer 1 overflows interrupt inhibit */TR1=1; / * starts timer */ES=1; / * serial port interrupts allowing */EA=1; / * always allows to interrupt */AD_CS=1; While (1) { if (flag1) { flag1=0; Convert_char_to_freq (); / * will receive the frequency character string convert binary number */output_ad7008 (freq) to; / * output frequency */delay_time (50); / * 0.5 second */the ad_channel1=0 that delays time; Tlc2543 (); For (s=0; S＜3; S++) {/* gathers first via voltage */delay_time (3); Ad_out_byte=0; Tlc2543 (); Ad_channel1+=ad_result; Ad_channel1/=3; Three */ad_channel2=0 that average of/* conversion; Ad_out_byte=0x10; Tlc2543 (); For (s=0; S＜3; S++) {/* gathers the second road voltage */delay_time (3); Ad_out_byte=0x10; Tlc2543 (); Ad_channel2+=ad_result; Ad_channel2/=3; Three */ad_channel3=0 that average of/* conversion; Ad_out_byte=0x20; Tlc2543 (); For (s=0; S＜3; S++) {/* gathers Third Road voltage */delay_time (3); Ad_out_byte=0x20; Tlc2543 (); Ad_channel3+=ad_result; Ad channel3/=3; / * conversion */the convert_ad_result_to_char () that averages for three times; Binary number after/* changes AD converts ASC II code character string */SBUF=send_buffer[send_buf_pointer++ to]; The data * of/* after host computer sends the AD conversion/void serial (void) interrupt 4/* serial port receive with send data subroutine */＜!--SIPO＜DP n=" 11 "〉--〉＜dp n=" d11 "/{ if (TI) { TI=0; If (send_buf_pointer＜12) SBUF=send_buf_pointer++]; / * sends 12 string data */return; If (RI) { RI=0; Recieve=SBUF;=' H ') buffer[buffer_pointer++]=recieve; / * character string finishes */else flag1=1 with ' H '; Return; Void delay_time (unsigned int n)/* time delay subroutine, time-delay 0.01 * n * second/{ unsigned int i; Unsigned int s=711*n; For (i=O; I＜s; I++) { } } void convert_char_to_freq ()/* will represent that the ASC sign indicating number of frequency converts the subroutine * of binary number/{ int i to; Freq=0; For (i=buffer_pointer-1; I＞=0; I--) freq+=((buffer[i]-48) * pow (10, buffer_pointer-1-i)); Buffer_pointer=0; Void convert_ad_result_to_char ()/* converts the binary result of AD conversion to the subroutine */{ send_buf_pointer=0 of ASC II sign indicating number; Send_buffer[0]=ad_channel1/1000+48; / * first via voltage conversion */send_buffer[1]=ad_channel1%1000)/100+48; Send_buffer[2]=(ad_channel1%100)/10+48; Send_buffer[3]=ad_channel1%10+48; Send_buffer[4]=ad_channel2/1000+48; / * the second road voltage conversion */send_buffer[5]=(ad_channel2%1000)/100+48; Send_buffer[6]=(ad_channel2%100)/10+48; Send_buffer[7]=ad_channel2%10+48; Send_buffer[8]=ad_channel3/1000+48; / * Third Road voltage conversion */send_buffer[9]=(ad_channel3%1000)/100+48; Send_buffer[10]=(ad_channel3%100)/10+48; Send_buffer[11]=ad_channel3%10+48; }

4. host computer procedure:

System's host computer procedure translation and compiling environment is Microsoft Visual C++6.0.Program is write under the Dialog of MFC structural framing.Because the file that MFC generates automatically is many, therefore only introduce the core of program, program annotation please refer to program the right "/* */" interior literal.

The program of opening serial ports following (serial port setting is: 9600bps, 8 bit data, 1 position of rest, no parity check position):

Void CSerialDlg ∷ OnOpenSerialPort () //TODO:Add your control notification handler code here CSerialDlg ∷ UpdateData (1); {/* serial ports is opened program */case 0:hCom=CreateFile (" COM1 " to switch (m_port_com_select), GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); If (hCom==INVALID_HANDLE_VALUE) MessageBox (" serial ports 1 is opened mistake! "); Else m_is_serial_port_open=1; Break; Case 1:hCom=CreateFile (" COM2 ", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); If (hCom=INVALID_HANDLE_VALUE) MessageBox (" serial ports 2 is opened mistake! "); Else m_is_serial_port_open=1; Break; Case 2:hCom=CreateFile (" COM3 ", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); If (hCom==INVALID_HANDLE_VALUE) MessageBox (" serial ports 3 is opened mistake! "); Else m_is_serial_port_open=1; Break; Case 3:hCom=CreateFile (" COM4 ", GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); If (hCom=INVALID_HANDLE_VALUE) MessageBox (" serial ports 4 is opened mistake! "); Else m_is_serial_port_open=1; Break; DCB dcb; Be serial port setting program */BOOL m_error below the/*; M_error=GetCommState (hCom ， ﹠amp; Amp; Dcb); If (! "); Dcb.BaudRate=CBR_9600; Dcb.ByteSize=8; Dcb.Parit=NOPARITY; Dcb.StopBits=ONESTOPBIT; M_error=SetCommState (hCom ， ﹠amp; Amp; Dcb); If (! "); M_error=SetCommMask (hCom, EV_RXCHAR|EV_TXEMPTY);＜!--SIPO＜DP n=" 13 "〉--〉＜dp n=" d13 "/if (! "); M_error=SetupComm (hCom, 0,0); If (! "); M_error=PurgeComm (hCom, PURGE_TXCLEAR|PURGE_RXCLEAR); If (! "); COMMTIMEOUTS m_com_time; M_com_time.ReadIntervalTimeout=1000; M_com_time.ReadTotalTimeoutConstant=0; M_com_time.ReadTotalTimeoutMultiplier=0; M_com_time.WriteTotalTimeoutConstant=2; M_com_time.WriteTotalTimeoutMultiplier=25; M_error=SetCommTimeouts (hCom ， ﹠amp; Amp; M_com_time); If (! "); }

The working routine of button is as follows:

Void CSerialDlg ∷ OnStartWork () //TODO:Add your control notification handler code here CSerialDlg ∷ UpdateData (1); / * obtains input value */if (m_is_serial_port_open==0) { MessageBox (" from man-machine interface does not have available serial ports at present, please open a serial ports! "); Return;=0﹠amp; Amp; ﹠amp; Amp;=1) { MessageBox (" please select the surveying instrument gear! "); Return; If (m_frquency_start==" ") { MessageBox (" please set initial frequency! "); Return; If (m_ffequency_end==" ") { MessageBox (" please set the termination frequency! "); Return; If (m_frequency_grads==0) { MessageBox (" please select the frequency steps distance! "); Return; {/* determines coordinate system scale */switch (m_coordinate_scale) { case 0:m_gain_value=100 to if (m_ceramic_select==0); Break; Case 1:m_gain_value=50; Break; Case 2:m_gain_value=20; Break; If (m_ceramic_select==1) { switch (m_coordinate_scale) { case 0:m_gain_value=10; Break; Case 1:m_gain_value=5; Break; Case 2:m_gain_value=2; Break; M_output_frequency=m_frequency_start; Int length;＜!--SIPO＜DP n=" 14 "〉--〉＜dp n=" d14 "/int i; Length=m_frequency_start.GetLength (); M_output_freq_low_long=0; For (i=0; I＜length; I++)/* with the ASC II sign indicating number of frequency convert to binary number */m_output_freq_low_long+=(m_frequency_start[i]-48) * pow (10, length-1-i); M_frequency_start_long=m_output_freq_low_long; Length=m_frequency_end.GetLength (); M_output_freq_high_long=0; For (i=0; I＜length; I++) { m_output_freq_high_long+=(m_frequency_end[i]-48) * pow (10, length-1-i); M_last_cos_fi=0; Initialization */the m_cos_fi=0 of/* one tittle; M_flag1=1; Sign change */the m_max_cos_fi=0 of/* sign admittance imaginary part; M_data_pointer=0; M_frequency_add_times=0; CSerialDlg ∷ OnClearScreen (); Paint_pic (); CDC*pdc; Pdc=GetDlgItem (IDC_GRAPH)-＞GetDC (); Pdc-＞TextOut (302,134, m_frepuency_start); / * on coordinate display frequency initial sum stop value */pdc-＞TextOut (660,134, m_frequency_end); Float ss=(m_output_freq_high_long-m_output_freq_low_long)/m_frequency_grads; M_x_axis_nterval=400/ss; SetTimer (ID_CLOCK_TIMER, 600, NULL); The timer * that/* setting program begins to scan/}

Program is carried out the working routine following (time interval of program scanning is produced by timer) that frequency sweeping is drawn:

The program of carrying out the data preservation in the program is as follows:

Void CSerialDlg ∷ OnSaveData () //TODO:Add your control notification handler code here CString path, name; CString save_data=" frequency (Hz) tCos (fi) tG (ms) t tB (ms) t tR (ohm) t tX (ohm) n "; Classification */CString the tmp of/* data form;=0) {/* all data in will scanning are deposited (the int i=0 of */in the character string; I＜m_data_pointer; I++) save_data+=m_data[i] .m_frequency; Save_data+=" t t "; Tmp.Format (" %f ", m_data[i] .m_cos_fi); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_data[i] .m_G); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_data[i] .m_B); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_data[i] .m_R); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_data[i] .m_X);＜!--SIPO＜DP n=" 19 "〉--〉＜dp n=" d19 "/save_data+=tmp; Save_data+=" n "; Save_data+=" n "; Tmp=" Syntonic F (Hz) Cos (fi) G (ms) B (ms) R (ohm) X (ohm) n "; The form classification */save_data+=tmp of/* tuning-points data; / * is following to be the data */save_data+=m_syntonic_freq of tuning-points; Save_data+=" t "; Tmp.Format (" %f ", m_max_cos_fi); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_syntonic_g); Save_data+=tmp; Save_data+=" t; Tmp.Format (" %f ", m_syntonic_b); Save_data+=tmp; Save_data+=" t; Tmp.Format (" %f ", m_syntoni_r); Save_data+=tmp; Save_data+=" t "; Tmp.Format (" %f ", m_syntonic_x); Save_data+=tmp; Save_data+=" n "; CFileDialog dlg (true, " RTF ", NULL, OFN_OVERWRITEPROMPT, NULL, NULL); / * opens program and preserves dialog box, with data be saved in */if in the file (dlg.DoModal ()==IDOK) { path=dlg.GetPathName (); Name=dlg.GetFileName (); FILE*FileHandle=fopen (path.GetBufferr (0), " wb "); Fwrite (save_data.GetBuffer (0), save_data.GetLength (), 1, FileHandle); Fllose (FileHandle);

The subroutine that the coordinate figure of click place is shown is as follows:

Void CSerialDlg ∷ OnMouseMove (UINT nFlags.CPoint point) //TODO:Add your message handler code here and/or call default if ((nFlags﹠amp; Amp; MK_LBUTTON)==MK_LBUTTON) { {/* measures gear 1*/if (point.x＜303), and {/* click place is coordinate left-half */m_pointer_g=((float) point.x-13)/m_gain_value to if (m_ceramic_select==0); M_pointer_b=375-(float) point.y)/m_gain_value; M_pointer_f=0; {/* click place is coordinate right half part */m_pointer_g=(375-(float) point.y) * 2/m_gain_value to if (point.x＞303); M_pointer_b==(375-(float) point.y) * 2/m_gain_value; Float qq=(float) (m_frequency_grads* (point.x-303))/m_x_axis_interval;＜!--SIPO＜DP n=" 20 "〉--〉＜dp n=" d20 "/m_pointer_f=(int) qq+m_frequency_start_long; {/* measures gear 2 to else{ if (point.x＜303), and click place is coordinate left-half */m_pointer_g=((float) point.x-13)/m_gain_value; M_pointer_b=(375-(float) point.y)/m_gain_value; {/* click place is coordinate right half part */m_pointer_g=(375-(float) point.y) * 2/m_gain_value to if (point.x＞303); M_pointer_b=(375-(float) point.y) * 2/m_gain_value; Float pp=(float) (m_frequency_grads* (point.x-303))/m_x_axis_interval; M_pointer_f=(int) pp+m_frequency_star_long; CSerialDlg ∷ UpdateData (0); }

Claims (1)

1. device that is used for measuring the piezoelectric ceramic transducer admittance circle diagram, wherein hardware and PC software are combined, finish piezoelectric ceramic transducer admittance data acquisition function by hardware components, finish drawing and data analysis function by software section, two parts are by computing machine serial port mutual communication, be characterised in that: adopt piezoelectric ceramic transducer is connected with variable resistor, obtain current value on the piezoelectric ceramic transducer by the magnitude of voltage on the variable resistor, record electric current and voltage by piezoelectric ceramic transducer and obtain impedance under the current frequency, resistance value is got the admittance value that just obtains under the current frequency reciprocal;

Have in the metering circuit:

1). signal generating circuit, adopt Direct Digital frequency synthesis technology to obtain sinusoidal signal, 89C51 does frequency control with single chip computer AT, signal is amplified the sinusoidal signal of acquisition with power operational amplifier;

2). computing and data acquisition circuit comprise peak-detector circuit and phase detecting circuit, peak-detector circuit comprises a high speed operation amplifier, a low speed operational amplifier and two fast recovery diodes, is used to detect the crest voltage of the sinusoidal signal of dynamic change; Phase detecting circuit adopts analog multiplier, is used to detect the phase difference value of two-way sine wave;

3). telecommunication circuit, as the communication slave computer, computing machine sends instruction by computer software to slave computer as the communication host computer with single-chip microcomputer, after the slave computer execution command, the data that collect is sent to host computer;

The data that the software processes of using employing Microsoft Visual C++6.0 to write on computers collects, obtain the admittance data of piezoelectric ceramic transducer, on computer display, make admittance circle diagram, thereby piezoelectric ceramic transducer is carried out the parameter extraction of specificity analysis and piezoelectric ceramic transducer.

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