CN212031354U - Piezoelectric impedance measurement data acquisition device - Google Patents
Piezoelectric impedance measurement data acquisition device Download PDFInfo
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- CN212031354U CN212031354U CN202020643677.8U CN202020643677U CN212031354U CN 212031354 U CN212031354 U CN 212031354U CN 202020643677 U CN202020643677 U CN 202020643677U CN 212031354 U CN212031354 U CN 212031354U
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Abstract
The utility model discloses a piezoelectric impedance measurement data acquisition device relates to piezoelectric impedance real-time measurement, data storage and transmission device, and the purpose is in order to overcome the problem that the existing piezoelectric impedance measurement device is bulky and can not be miniaturized, and comprises a main control circuit, a digital-to-analog conversion circuit, a voltage following circuit, a current-voltage conversion circuit, a true effective value detection circuit, a phase discrimination circuit and an analog-to-digital acquisition circuit; the main control circuit is electrically connected with the digital-to-analog conversion circuit; the digital-to-analog conversion circuit is electrically connected with the phase discrimination circuit and the voltage follower circuit at the same time; the voltage following circuit is electrically connected with the structural body to be detected and the true effective value detection circuit at the same time; the structure body to be tested is electrically connected with the current-voltage conversion circuit; the current-voltage conversion circuit is electrically connected with the phase discrimination circuit and the true effective value detection circuit at the same time; the phase discrimination circuit is electrically connected with the analog digital acquisition circuit; the true effective value detection circuit is electrically connected with the analog digital acquisition circuit end; the analog digital acquisition circuit is electrically connected with the main control circuit.
Description
Technical Field
The utility model relates to a nondestructive test technical field, concretely relates to piezoelectric impedance real-time measurement, data storage and transmission device.
Background
Among a plurality of structural local tiny damage identification methods, the damage identification method based on the piezoelectric impedance principle is very sensitive to structural local state changes, is not easily interfered by external environment, does not depend on model analysis, is suitable for complex engineering structure detection, is also suitable for online monitoring, and is a simple, convenient and reliable structural damage identification method.
In the damage identification method based on the piezoelectric impedance principle, changes such as the local rigidity of the structure are expressed as changes in the mechanical impedance of the structure. The piezoelectric sensor is adhered to the structure to generate mechanical coupling with the structure, and then the mechanical impedance of the structure is converted into the electrical impedance of the piezoelectric sensor through the self force-electricity coupling effect of the piezoelectric sensor. Changes in electrical impedance reflect changes in the mechanical impedance of the structure, and thus damage or other changes in the state of the structure. One of the key steps of the piezoelectric impedance method is the measurement of the impedance characteristic curve of the piezoelectric sensor. At present, in a structural damage identification test based on the piezoelectric impedance principle in a laboratory, an impedance analyzer is generally adopted to measure characteristic curves such as the electrical impedance of a piezoelectric sensor, such as a commonly used Agilent 4294A precision impedance analyzer (Agilent 4294A), a Wayne Kerr WK6550B precision impedance analyzer, and the like. Although the device has wide measuring frequency range, high resolution and rich functions. For example, 4294A measures frequency from 40kHz to 110MHz, and the frequency resolution is 1 mHz. However, when the above-mentioned device is applied to an actual engineering structure, there are many problems, such as that the 4294A driving voltage is low (below 1V), and when the piezoelectric sensor is attached to or embedded in a large structure for monitoring, if the piezoelectric sensor cannot be excited sufficiently, the measured electrical impedance signal cannot accurately reflect the actual damage condition of the structure. Meanwhile, the equipment has the defects of high price, large volume, heavy weight and the like, all functions of the equipment are not used in actual measurement, and the measurement range and the measurement precision far exceed the measurement requirement. Therefore, the large-scale equipment is difficult to be applied to the actual engineering structure field to carry out a large number of sensor acquisition and carry out structural damage identification in real time.
Based on this, some researchers have developed highly integrated, small-sized and portable impedance analyzers, such as Naserodin Sepehry, which measure piezoelectric impedance curves below 100kHz using an AD5933 chip (Naserodin Sepehry, Mahnaz Shamshirsz and Ali basic. Experimental and the organic analysis in ambient-based Structural Health Monitoring with varying impedance Monitoring,2010,10(6): 573-585), but are limited to principle circuits and do not form devices with complete functions. The utility model discloses a piezoelectric impedance measuring equipment for structure health monitoring "(grant No.: ZL201520331939.6) used arbitrary waveform generator and digital oscilloscope, did not carry out miniaturized detailed circuit and functional design, and still bulky, with high costs.
A new patent "a miniature piezoelectric impedance device and method for on-line health monitoring" (application No. 201811420828.7) discloses a miniature device based on AD5933 chip, but the measurement range is small, and the detailed design on specific functions, such as data storage and transmission, is not made.
SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming current piezoelectric impedance measuring device is bulky, the unable miniaturized problem, provide a piezoelectric impedance measurement data acquisition device.
The utility model discloses a piezoelectric impedance measurement data acquisition device, which comprises a main control circuit, a digital-to-analog conversion circuit, a voltage following circuit, a current-voltage conversion circuit, a true effective value detection circuit, a phase discrimination circuit and an analog-to-digital acquisition circuit;
the sine signal output end of the main control circuit is electrically connected with the digital signal input end of the digital-to-analog conversion circuit;
the first homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit is electrically connected with the reference signal input end of the phase discrimination circuit, and the second homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit is electrically connected with the voltage buffering input end of the voltage follower circuit and is buffered through the voltage follower circuit;
the voltage buffer output end of the voltage following circuit is electrically connected with the measurement signal input end of the structural body to be detected and the first detection signal input end of the true effective value detection circuit at the same time;
the return signal output end of the structure body to be tested is electrically connected with the current signal input end of the current-voltage conversion circuit, and current-voltage conversion is carried out through the current-voltage conversion circuit;
the voltage signal output end of the current-voltage conversion circuit is electrically connected with the measurement return signal input end of the phase discrimination circuit and the second detection signal input end of the true effective value detection circuit at the same time;
the phase difference signal output end of the phase discrimination circuit is electrically connected with the first analog acquisition signal input end of the analog-digital acquisition circuit;
the excitation signal true effective value output end of the true effective value detection circuit is electrically connected with a second analog acquisition signal input end of the analog-digital acquisition circuit; the return signal true effective value output end of the true effective value detection circuit is electrically connected with a third analog acquisition signal input end of the analog-digital acquisition circuit;
the digital acquisition signal output end of the analog-digital acquisition circuit is electrically connected with the digital acquisition signal input end of the main control circuit.
The utility model has the advantages that: a small piezoelectric impedance measuring device is provided, which has the functions of real-time acquisition, storage and transmission of piezoelectric impedance signals and temperature signals. The method can be used for portable piezoelectric impedance measurement in a laboratory or on site, and can also be used for long-term online piezoelectric impedance measurement in a laboratory or on site.
The device can scan 1000 frequency points at one time and has high response speed. The sensor is matched with a piezoelectric sensor and a temperature sensor for use, can be conveniently used for on-site detection or real-time online monitoring of a structure, and can provide temperature data and electrical impedance data for judging the tiny change of the structure state, so that the local tiny damage identification of the structure is realized. The multifunctional portable multifunctional desk has the characteristics of complete functions, simple structure, light weight, small volume, low price, easiness in operation, good stability, wide application range and the like.
Drawings
Fig. 1 is an electrical schematic diagram of a piezoelectric impedance measurement data acquisition device according to the present invention, in which a DUT represents a structure to be measured, which is composed of a matching capacitor, a shielding cable, and a piezoelectric sensor;
fig. 2 is a circuit diagram of a main control circuit in the piezoelectric impedance measurement data acquisition device of the present invention;
fig. 3 is a schematic diagram of a combination of the digital-to-analog conversion circuit, the voltage follower circuit, the true effective value detection circuit and the phase discrimination circuit in the piezoelectric impedance measurement data acquisition device of the present invention, wherein CON1A is a connection pin with the main control circuit;
fig. 4 is a schematic diagram of a combination of a current-voltage conversion circuit, a true effective value detection circuit, a phase demodulation circuit and an analog-digital acquisition circuit in the piezoelectric impedance measurement data acquisition device of the present invention, wherein CON1B is a connection pin with a main control circuit;
fig. 5 is a working schematic diagram of a piezoelectric impedance measurement data acquisition device of the present invention;
FIG. 6 is a graph showing the conductance (G) in the upper solid line and the susceptance (B) in the lower broken line of the graph, in which the conductance (G) is shown by the upper line, in the conductance-admittance curve (50 kHz-1 MHz) obtained by measuring a structure by the present apparatus; wherein the abscissa represents the frequency of the excitation voltage signal and the ordinate represents the admittance.
Detailed Description
In a first specific embodiment, the piezoelectric impedance measurement data acquisition device in this embodiment includes a main control circuit 1, a digital-to-analog conversion circuit 2, a voltage follower circuit 3, a current-voltage conversion circuit 4, a true effective value detection circuit 5, a phase discrimination circuit 6, and an analog-digital acquisition circuit 7;
the sine signal output end of the main control circuit 1 is electrically connected with the digital signal input end of the digital-to-analog conversion circuit 2;
a first homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit 2 is electrically connected with a reference signal input end of the phase discrimination circuit 6, and a second homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit 2 is electrically connected with a voltage buffering input end of the voltage follower circuit 3 and is buffered by the voltage follower circuit 3;
the voltage buffering output end of the voltage following circuit 3 is electrically connected with the measuring signal input end of the structural body to be detected 8 and the first detection signal input end of the true effective value detection circuit 5 at the same time;
the return signal output end of the structural body to be tested 8 is electrically connected with the current signal input end of the current-voltage conversion circuit 4, and current-voltage conversion is carried out through the current-voltage conversion circuit 4;
the voltage signal output end of the current-voltage conversion circuit 4 is electrically connected with the measurement return signal input end of the phase discrimination circuit 6 and the second detection signal input end of the true effective value detection circuit 5;
the phase difference signal output end of the phase discrimination circuit 6 is electrically connected with the first analog acquisition signal input end of the analog-digital acquisition circuit 7;
the excitation signal true effective value output end of the true effective value detection circuit 5 is electrically connected with a second analog acquisition signal input end of the analog-digital acquisition circuit 7; the true effective value output end of the return signal of the true effective value detection circuit 5 is electrically connected with the third analog acquisition signal input end of the analog-digital acquisition circuit 7;
the digital acquisition signal output end of the analog digital acquisition circuit 7 is electrically connected with the digital acquisition signal input end of the main control circuit 1.
Specifically, the use method for measuring the corrosion of metal by using the novel device is characterized in that a piezoelectric ceramic sensor is attached to a vulnerable part of the metal, and the piezoelectric ceramic sensor is connected to the novel piezoelectric impedance measurement data acquisition device by using a shielding cable to acquire impedance data. The device can transmit the frequency spectrum data of the electric admittance (the reciprocal of the electric impedance) to a remote industrial personal computer through a network cable and a switch for displaying, storing and analyzing, as shown in figure 6.
As shown in fig. 1, the present novel piezoelectric impedance measurement data acquisition device is a small piezoelectric impedance measurement device, and its main function circuit includes: the circuit comprises a main control circuit 1, a digital-to-analog conversion circuit 2, a voltage follower circuit 3, a current-voltage conversion circuit 4, a true effective value detection circuit 5, a phase discrimination circuit 6 and an analog-digital acquisition circuit 7.
The device can generate an excitation voltage signal with 50 kHz-1 MHz and a peak value of 5V to continuously measure the structural body 8 to be measured on line.
The structure 8 to be measured in fig. 1 is composed of a matching capacitor, a shielding cable and a piezoelectric sensor, wherein the piezoelectric sensor is used as an impedance sensor, and the piezoelectric sensor can adopt a piezoelectric ceramic piece and generates a response electric signal after an inverse piezoelectric effect. And the matching capacitor is used for ensuring that the impedance value of the piezoelectric sensor is within the measurement range of the piezoelectric impedance measurement data acquisition device.
The functions of the circuits of the device are explained as follows:
the main control circuit 1 adopts an FPGA core board, and can realize control of the whole system.
The digital-to-analog conversion circuit 2 adopts a 14-bit double-channel DA conversion chip, and is combined with an FPGA core board to construct a double-channel in-phase sinusoidal signal source, so as to generate 50 kHz-1 MHz alternating-current scanning signals with adjustable amplitude, frequency and frequency sweeping ranges.
The voltage follower circuit 3 is used for buffering, isolating and improving the loading capacity of the system.
The current-voltage conversion circuit 4 converts a current signal, which is not easily directly measured, into a voltage signal, which is easily directly measured.
The true effective value detection circuit 5 sends the two paths of measured actual true effective values to the analog digital acquisition circuit 7 in the form of voltage.
The phase detection circuit 6 performs measurement of a phase difference (impedance angle) between a return voltage signal (measurement return signal) and a reference voltage signal (reference signal), and calculates a resistance component and a reactance component therefrom.
The analog-digital acquisition circuit 7 converts three paths of voltage analog quantity into digital quantity and sends the digital quantity to the main control circuit 1, so that acquisition of piezoelectric impedance data is completed.
Meanwhile, the device can be additionally provided with a wireless transmission circuit 10 and a display circuit 11.
The wireless transmission circuit is used for data interaction between the upper computer 12 and the main control circuit 1, the upper computer 12 transmits configuration data to the main control circuit 1 through an antenna, excitation signal parameters (which can be not specified and adopt fixed parameters) sent by the main control circuit 1 are specified, and the main control circuit 1 transmits impedance data to the upper computer through the wireless transmission circuit for real-time display and storage.
The display circuit 11, i.e., a display device such as a liquid crystal panel, is connected to the display data output terminal of the main control circuit 1, and can display the impedance data in real time.
The wireless sensor network measurement system has the wired and wireless network connection function, and measurement data can be sent to an upper computer through a network protocol, so that the data can be conveniently displayed and analyzed. By setting the measurement interval time, the result may be sent periodically. When the electrical impedance signal is measured, the temperature value of the position of the piezoelectric sensor can be measured, and the temperature value is used for later-stage temperature influence analysis and temperature influence elimination.
Best embodiment, this embodiment is a further description of the first embodiment, and this embodiment further includes a temperature sensor 9;
the temperature signal output end of the temperature sensor 9 is electrically connected with the temperature signal input end of the main control circuit 1.
Specifically, the structural mechanical impedance and the electrical impedance of the piezoelectric sensor are both sensitive to temperature, a specific measurement signal is easily influenced by temperature, temperature factors need to be eliminated in practical application, and the conventional piezoelectric impedance measurement device has no temperature measurement function. Therefore, a temperature sensor 9 is added for detecting the current ambient temperature and using this temperature for calibration.
The temperature sensor 9 may be a specific type of temperature sensor, e.g. collecting the electrical impedance data while collecting the temperature at the piezoelectric sensor, which may be used for subsequent analysis to eliminate the influence of temperature on the electrical impedance measurement.
The temperature of the measured object is measured, so that temperature compensation is added, and measurement errors caused by temperature changes are eliminated.
In this embodiment, the main control circuit 1 is an EP4CE15F17C8N processor.
In the present embodiment, the digital-to-analog conversion circuit 2 is an AD9767 digital-to-analog converter.
In the present embodiment, the true effective value detection circuit 5 is an AD637 rms dc converter.
In this embodiment, the phase detection circuit 6 is an AD8302 amplitude-phase detector.
In this embodiment, the analog-digital acquisition circuit 7 is an AD7606 synchronous sampler.
Specifically, as shown in fig. 1, this novel hardware includes power supply (12/24V), master control circuit, digital-to-analog conversion circuit, voltage follower circuit, matching capacitor, shielded cable, piezoelectric sensor, current-to-voltage conversion circuit, true effective value detection circuit, phase discrimination circuit, AD acquisition circuit, wireless transmission circuit, temperature acquisition circuit and power supply conversion circuit.
The above-mentioned cooperative work flow of the circuits is shown in fig. 5.
As shown in fig. 2 to 4, the main control circuit 1 is an FPGA core board, and is a development board using EP4CE15F17C8N as a core chip. The control of the whole system is realized, including the realization of a sine signal generator and the excitation of a digital-to-analog conversion circuit 2; control, data reception and data processing of the analog digital acquisition circuit 7; the temperature measurement is realized by the excitation and data transmission of a temperature measurement circuit (temperature change); the control of the wireless serial port circuit (wireless transmission circuit) realizes the remote transmission of data.
As shown in fig. 3, the digital-to-analog conversion circuit 2 generates two paths of in-phase sinusoidal frequency sweep signals by using AD9767 of ADI, one path of the in-phase sinusoidal frequency sweep signals is buffered by the voltage follower circuit 3 and then respectively sent to the structural body to be measured 8 and the true effective value detection circuit 5 to measure the actual true effective value of the excitation signal, and the other path of the in-phase sinusoidal frequency sweep signals is taken as a reference signal and sent to the phase discrimination circuit 6; and the signal that returns from the structural body 8 to be measured also divides into two-way after the current-voltage switching circuit 4 circuit, send into the phase discrimination circuit 6 and compare with reference signal and get the phase difference (impedance angle) in one way, send into the real effective value detection circuit 5 to detect the actual real effective value of the return signal in another way.
As shown in fig. 4, the phase detection circuit 6 converts the measured phase difference into a voltage value by using AD8302 of ADI corporation, and sends the voltage value to the analog-digital acquisition circuit 7;
as shown in fig. 4, the true effective value detection circuit 5 adopts AD637 of ADI corporation to send two paths of measured actual true effective values to the analog-digital acquisition circuit 7 in the form of voltage;
as shown in fig. 4, the analog-digital acquisition circuit 7 converts three voltage analog quantities into digital quantities by using AD7606 of ADI corporation, and sends the digital quantities to the FPGA core board of the main control circuit 1.
Claims (7)
1. A piezoelectric impedance measurement data acquisition device is characterized by comprising a main control circuit (1), a digital-to-analog conversion circuit (2), a voltage follower circuit (3), a current-voltage conversion circuit (4), a true effective value detection circuit (5), a phase discrimination circuit (6) and an analog-digital acquisition circuit (7);
the sine signal output end of the main control circuit (1) is electrically connected with the digital signal input end of the digital-to-analog conversion circuit (2);
a first homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit (2) is electrically connected with a reference signal input end of the phase discrimination circuit (6), and a second homodromous sine frequency sweeping signal output end of the digital-to-analog conversion circuit (2) is electrically connected with a voltage buffering input end of the voltage follower circuit (3) and is buffered by the voltage follower circuit (3);
the voltage buffering output end of the voltage following circuit (3) is electrically connected with the measuring signal input end of the structure body to be detected (8) and the first detection signal input end of the true effective value detection circuit (5) at the same time;
the return signal output end of the structure body to be tested (8) is electrically connected with the current signal input end of the current-voltage conversion circuit (4), and current-voltage conversion is carried out through the current-voltage conversion circuit (4);
the voltage signal output end of the current-voltage conversion circuit (4) is electrically connected with the measurement return signal input end of the phase discrimination circuit (6) and the second detection signal input end of the true effective value detection circuit (5) at the same time;
the phase difference signal output end of the phase discrimination circuit (6) is electrically connected with the first analog acquisition signal input end of the analog-digital acquisition circuit (7);
the excitation signal true effective value output end of the true effective value detection circuit (5) is electrically connected with the second analog acquisition signal input end of the analog-digital acquisition circuit (7); the return signal true effective value output end of the true effective value detection circuit (5) is electrically connected with a third analog acquisition signal input end of the analog-digital acquisition circuit (7);
and the digital acquisition signal output end of the analog-digital acquisition circuit (7) is electrically connected with the digital acquisition signal input end of the main control circuit (1).
2. A piezoelectric impedance measurement data acquisition device according to claim 1, further comprising a temperature sensor (9);
and the temperature signal output end of the temperature sensor (9) is electrically connected with the temperature signal input end of the main control circuit (1).
3. A piezoelectric impedance measurement data acquisition device according to claim 1 or 2, wherein the main control circuit (1) is an EP4CE15F17C8N processor.
4. A piezoelectric impedance measurement data acquisition device according to claim 1 or 2, wherein the digital-to-analog conversion circuit (2) is an AD9767 digital-to-analog converter.
5. A piezoelectric impedance measurement data acquisition device according to claim 1 or 2, wherein the true effective value detection circuit (5) is an AD637 rms dc converter.
6. A piezoelectric impedance measurement data acquisition device according to claim 1 or 2, characterized in that the phase detection circuit (6) is an AD8302 amplitude-phase detector.
7. A piezoelectric impedance measurement data acquisition device according to claim 1 or 2, wherein the analog-digital acquisition circuit (7) is an AD7606 synchronous sampler.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115327233A (en) * | 2022-09-06 | 2022-11-11 | 乌镇实验室 | Novel piezoelectric resonance impedance measuring system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115327233A (en) * | 2022-09-06 | 2022-11-11 | 乌镇实验室 | Novel piezoelectric resonance impedance measuring system |
| CN115327233B (en) * | 2022-09-06 | 2024-02-09 | 乌镇实验室 | Piezoelectric resonance impedance measurement system |
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