Eddy current nondestructive testing device

Abstract

The present invention provides an eddy current nondestructive testing device, comprising: a central module, a digital-to-analog conversion module, a power amplifier module, an excitation coil, an acquisition module, a preamplifier module, an analog-to-digital conversion module, and a display module, wherein: the digital-to-analog conversion module is connected to the output end of the central module; the power amplifier module is connected to the output end of the digital-to-analog conversion module; the excitation coil is connected to the output end of the power amplifier module to generate an excitation signal to perform excitation disturbance on the object to be tested; the acquisition module collects the induced signal; the preamplifier module is connected to the output end of the acquisition module; the analog-to-digital conversion module is connected to the output end of the preamplifier module to obtain defect information of the object to be tested by performing calculations and processing on the digitized excitation parameter signal; and the display module is connected to the output end of the central module to display and control the defect information. The device is easy to operate, obtains accurate and reliable results, has a high system integration level, and reduces hardware costs.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic nondestructive testing, in particular to an eddy current nondestructive testing device. Background Art

[0002] Electromagnetic nondestructive testing (NDT) is a method that uses changes in a material's electromagnetic properties to detect defects and test its performance. Its fundamental principles are based on the theory of electromagnetism. Modern electromagnetic testing, particularly eddy current testing, is based on Maxwell's equations.

[0003] Tunnel magnetoresistance (TMR) is a type of thin-film magnetoresistive sensor based on the quantum tunneling effect. Developed in the 1990s to increase HDD density, this type of magnetic sensor was commercialized in the hard drive market in 2004. Around 2012, with the advancement of TMR sensor technology, linear TMR sensors were introduced to the industrial market. However, the differential electrical signal directly transmitted from the TMR is still very small and easily drowned out by various noise sources. Therefore, the application of weak signal detection technologies in eddy current nondestructive testing systems is essential.

[0004] Phase-locked amplification technology is a widely used weak signal detection technology. Compared with common narrowband filtering method and sampling integration and digital averaging method, phase-locked amplification method has better detection ability, stronger stability and higher detection accuracy. It can detect weak signal with a signal-to-noise ratio of 10 -5 The weak signal is equivalent to a bandpass filter with an adjustable center frequency and a bandwidth less than 0.004HZ.

[0005] At present, commercial lock-in amplifiers on the market need to be based on versatility and multifunctionality, and mostly use modular design. The equipment is large and expensive, which makes it difficult to adapt to the needs of today's market for fast, low-cost, and on-site electromagnetic non-destructive testing. Summary of the Invention

[0006] In view of the above-mentioned shortcomings of the prior art, the object of the present invention is to provide an eddy current non-destructive testing device to solve the problems of high cost, cumbersome testing and difficult on-site testing of the modular electromagnetic non-destructive testing device in the prior art.

[0007] To achieve the above-mentioned and other related objectives, the present invention provides an eddy current nondestructive testing device, which comprises at least: a central module, a digital-to-analog conversion module, a power amplifier module, an excitation coil, an acquisition module, a preamplifier module, an analog-to-digital conversion module, and a display module, wherein:

[0008] The digital-to-analog conversion module is connected to the output end of the central module and converts the digital excitation parameter signal output by the central module into an analog signal;

[0009] The power amplifier module is connected to the output end of the digital-to-analog conversion module to amplify the analog signal;

[0010] The excitation coil is connected to the output end of the power amplifier module to generate an excitation signal for exciting the object to be tested;

[0011] The acquisition module acquires the induction signal generated by the object to be tested under the excitation disturbance;

[0012] The preamplifier module is connected to the output end of the acquisition module to amplify the output signal of the acquisition module;

[0013] The analog-to-digital conversion module is connected to the output end of the preamplifier module, converting the output signal of the preamplifier module into a digital signal and transmitting it to the input end of the hub module;

[0014] The central module obtains defect information of the object to be tested based on the digital signal and the digitized excitation parameter signal;

[0015] The display module is connected to the output end of the central module to display the defect information.

[0016] Optionally, the central module is a field programmable logic gate array chip, a quantum processor chip, a dedicated integrated circuit chip, or a microprocessor chip.

[0017] Optionally, the central module includes a control communication unit, a signal generating unit and a digital phase-locked amplification unit, wherein the control communication unit receives parameter instructions sent by the host computer and transmits defect information and display control signals to the display module; the signal generating unit generates the digital excitation parameter signal based on the received parameter instructions, wherein the digital excitation parameter signal includes a reference signal 1 and a reference signal 2, and the reference signal 1 and the reference signal 2 have equal frequencies and are strictly orthogonal; the digital phase-locked amplification unit performs correlation and arithmetic operations on the digital signal.

[0018] Optionally, the digital phase-locked amplification unit includes a first correlator, a second correlator and an arithmetic operator, wherein: the first correlator receives the reference signal 1 and the digital signal; the second correlator receives the reference signal 2 and the digital signal; and the arithmetic operator is connected to the output ends of the first correlator and the second correlator.

[0019] Optionally, the first correlator and the second correlator each include a multiplier and a low-pass filter, wherein: the multiplier in the first correlator receives the reference signal 1 and the digital signal, outputs them to the low-pass filter in the first correlator after multiplication, and outputs them to the arithmetic operator after filtering; the multiplier in the second correlator receives the reference signal 2 and the digital signal, outputs them to the low-pass filter in the second correlator after multiplication, and outputs them to the arithmetic operator after filtering.

[0020] Optionally, the communication protocol of the control communication unit is RS-232 protocol, RS-422 protocol, RS-485 protocol or Bluetooth.

[0021] Optionally, the signal generating unit is a direct digital frequency synthesizer.

[0022] Optionally, the excitation coil is a planar double D-shaped excitation coil.

[0023] Optionally, the acquisition module is a tunnel magnetoresistive sensor, and the number of the tunnel magnetoresistive sensors is N, where N is a natural number greater than or equal to 1.

[0024] Optionally, the number of channels of the preamplifier module is N.

[0025] Optionally, the display module is a display, a mobile phone, a tablet, or a host computer.

[0026] As described above, the eddy current nondestructive testing device of the present invention has the following beneficial effects:

[0027] 1) The eddy current nondestructive testing device of the present invention generates eddy current disturbances in the object to be tested through an excitation coil. The magnetic field generated by the eddy current disturbances is captured by an acquisition module and input into a digital lock-in amplifier unit after pre-amplification and analog-to-digital conversion. After calculation, defect information of the object to be tested is obtained. The device is easy to operate and the results obtained are accurate and reliable.

[0028] 2) The eddy current nondestructive testing device of the present invention adopts a central module to construct a digital phase-locked amplification unit, which has high system integration and reduces hardware costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Shown is a functional structure diagram of the eddy current non-destructive testing device provided by the present invention.

[0030] Figure 2 Shown is a schematic diagram of the internal functional structure of the hub module provided by the present invention.

[0031] Figure 3 Shown is a schematic diagram of the structure of the excitation coil provided by the present invention.

[0032] Figure 4 Shown is a functional structure diagram of the digital phase-locked amplifier unit provided by the present invention.

[0033] Component number description

[0034] 1 Central module

[0035] 11 Control communication unit

[0036] 12 signal generation unit

[0037] 13 Digital lock-in amplifier unit

[0038] 131 First Correlator

[0039] 132 Second Correlator

[0040] 133 Arithmetic Unit

[0041] 2 Digital-to-analog conversion module

[0042] 3 Power amplifier module

[0043] 4 Excitation coil

[0044] 5. Acquisition Module

[0045] 6 Preamplifier Module

[0046] 7 Analog-to-digital conversion module

[0047] 8 Display Module DETAILED DESCRIPTION

[0048] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0049] See also Figures 1 to 4 It should be noted that the diagrams provided in this embodiment are merely schematic illustrations of the basic concept of the present invention. Therefore, the diagrams only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0050] like Figures 1 to 4As shown, this embodiment provides an eddy current nondestructive testing device, which includes at least: a central module 1, a digital-to-analog conversion module 2, a power amplifier module 3, an excitation coil 4, an acquisition module 5, a preamplifier module 6, an analog-to-digital conversion module 7 and a display module 8, wherein:

[0051] like Figure 1 As shown, the digital-to-analog conversion module 2 is connected to the output end of the central module 1, and converts the digital excitation parameter signal output by the central module 1 into an analog signal; the power amplifier module 3 is connected to the output end of the digital-to-analog conversion module 2, and amplifies the analog signal; the excitation coil 4 is connected to the output end of the power amplifier module 3, and generates an excitation signal for excitation disturbance of the object to be tested.

[0052] Specifically, as an example, Figure 1 and Figure 2As shown, the central module 1 is a field programmable logic gate array chip or a quantum processor chip or a dedicated integrated circuit chip or a microprocessor chip. More specifically, the central module 1 is provided with a control communication unit 11, a signal generating unit 12 and a digital phase-locked amplifier unit 13, wherein the control communication unit 11 receives the parameter instructions sent by the host computer, and transmits the defect information and the display control signal to the display module 8. Furthermore, the communication protocol of the control communication unit 11 is RS-232 protocol or RS-422 protocol or RS-485 protocol or Bluetooth; the signal generating unit 12 generates the digital excitation parameter signal from the received parameter instruction, wherein the digital excitation parameter signal includes a reference signal 1 and a reference signal 2, and the reference signal 1 and the reference signal 2 have equal frequencies and are strictly orthogonal; further, the signal generating unit 12 is a direct digital frequency synthesizer, i.e., DDS (Direct Digital Frequency Synthesizer). Synthesizer); the digital phase-locked amplifier unit 13 performs correlation and arithmetic operations on the digital signal. Further, the digital phase-locked amplifier unit 13 includes a first correlator 131, a second correlator 132 and an arithmetic operator 133, wherein: the first correlator 131 receives the reference signal 1 and the digital signal; the second correlator 132 receives the reference signal 2 and the digital signal; the arithmetic operator 133 is connected to the output ends of the first correlator 131 and the second correlator 132, and further, the first The first correlator 131 and the second correlator 132 each include a multiplier and a low-pass filter, wherein: the multiplier in the first correlator 131 receives the reference signal 1 and the digital signal, outputs them to the low-pass filter in the first correlator 132 after multiplication, and outputs them to the arithmetic operator 133 after filtering; the multiplier in the second correlator 132 receives the reference signal 2 and the digital signal, outputs them to the low-pass filter in the second correlator 132 after multiplication, and outputs them to the arithmetic operator 133 after filtering.

[0053] It should be noted that when the central module 1 is a field programmable gate array chip, i.e., FPGA (Field Programmable Gate Array), it is used to convert the digital excitation parameter signal into an analog signal, set the parameter instruction of the excitation signal on the host computer, and transmit the parameter instruction to the control communication unit 11 in the FPGA through serial communication, wherein the communication protocol of the control communication unit 11 is RS-232 protocol or RS-422 protocol or RS-485 protocol or Bluetooth. It should be further noted that RS-232 protocol or RS-422 protocol or RS-485 protocol are all standard protocols for serial communication. The maximum communication distance of RS-232 protocol is 15 meters, and only one device can be connected; while the maximum communication distance of RS-422 protocol or RS-485 protocol is 1200 meters, and more than one device can be connected. In the application, the communication protocol of the control communication unit 11 is set according to the usage scenario. As long as the parameter instruction can be communicated, any communication protocol is applicable, not limited to this embodiment.

[0054] The control communication unit 11 then outputs the received parameter instruction to the signal generating unit 12, wherein the signal generating unit 12 is a direct digital frequency synthesizer, namely DDS (Direct Digital Synthesizer), such as Figure 4 As shown, the DDS generates two strictly orthogonal digital excitation reference signals, namely reference signal 1 and reference signal 2, wherein the reference signal 1 and reference signal 2 have the same frequency and are strictly orthogonal. The reference signal 1 and reference signal 2 are transmitted to the digital phase-locked amplifier unit 13, and the DDS transmits the reference signal 1 or the reference signal 2 to the digital-to-analog conversion module 2. It should be further explained that since the phase synchronization frequency of the reference signal 1 and the reference signal 2 is equal, for the convenience of description, the digital excitation reference signal is used here to refer to the reference signal 1 or the reference signal 2 transmitted to the digital-to-analog conversion module 2, and the digital-to-analog conversion module 2 converts the digital excitation reference signal into an analog signal. It should be supplemented that, with the development of semiconductor manufacturing technology, modules with the same functions as the digital-to-analog conversion module 2 and the analog-to-digital conversion module 7 can also be integrated into the FPGA chip to reduce the hardware area. The specific setting should take into account the actual applicable scenario and is not limited to this embodiment. It should be noted that when the central module 1 is a quantum processor chip or an application-specific integrated circuit chip (ASIC) or a microprocessor chip (MCU), the functions implemented are similar to those of FPGA and will not be described in detail here.

[0055] Specifically, as an example, Figure 3As shown, the excitation coil 4 is connected to the output end of the power amplifier module 3 to generate an excitation signal that can disturb the internal current of the ferromagnetic object. The excitation coil 4 is a planar double D-shaped excitation coil, which adopts PCB (Printed Circuit Board) technology and is composed of multiple strands of the same wire coil. It should be noted that the excitation coil 4 is usually also provided with excitation signal input and output pins, linear magnetic sensor pins and linear magnetic sensor. Figure 3 The excitation signal disturbs the object under test, and the object under test generates an induction signal after the excitation disturbance.

[0056] like Figure 1 As shown, the acquisition module 5 acquires the induction signal generated by the object to be tested under excitation disturbance; the preamplifier module 6 is connected to the output end of the acquisition module 5 to amplify the output signal of the acquisition module 5; the analog-to-digital conversion module 7 is connected to the output end of the preamplifier module 6 to convert the output signal of the preamplifier module 6 into a digital signal and transmit it to the input end of the central module 1; the central module 1 obtains the defect information of the object to be tested based on the digital signal and the digitized excitation parameter signal; the display module 8 is connected to the output end of the central module 1 to display the defect information.

[0057] Specifically, as an example, Figure 1 As shown, the acquisition module 5 is a tunnel magnetoresistive sensor, and the number of the tunnel magnetoresistive sensors is N, where N is a natural number greater than or equal to 1. It should be noted that the number of tunnel magnetoresistive sensors is designed based on the imaging requirements of the defective portion of the object to be tested. It can be set to three Z-direction tunnel magnetoresistive sensors for converting the induced signal (usually a magnetic field signal) perpendicular to the excitation coil 4 into a differential voltage signal. It can also be set to two, one, or more than three tunnel magnetoresistive sensors. The direction of the tunnel magnetoresistive sensors should be set according to the specific usage scenario and is not limited to this embodiment.

[0058] More specifically, the number of channels of the preamplifier module 6 is N. It should be noted that the preamplifier module 6 is configured based on the acquisition module 5. Therefore, the number of channels of the preamplifier module 6 must be equal to the number of acquisition modules 5 (the number of tunnel magnetoresistive sensors). Since the defect area of ​​the object to be tested may be a surface or an irregular solid, if the number of channels of the preamplifier module 6 is 1, the final image is only a line, making it difficult to determine the specific attributes of the defect area. It should be noted that the number of channels of the preamplifier module 6 should be set according to the attributes of the defect area of ​​the object to be tested and the required imaging requirements, such as resolution, and is not limited to this embodiment.

[0059] Specifically, as an example, Figure 1 As shown, the display module 8 is a display, a mobile phone, a tablet, or a host computer. It should be noted that the display module 8 is used to display the defects of the item to be tested. The display module 8 is displayed by the control communication unit 11 in the central module 1. The control communication unit 11 transmits the defect information of the item to be tested to the display module 8 through, for example, Bluetooth. It can also be displayed on the host computer interface, or using the RS-232 protocol, RS-422 protocol, RS-485 protocol, or File Transfer Protocol (FTP) for transmission. Any method that can display and control the defects of the item to be tested is applicable, and is not limited to this embodiment.

[0060] Specifically, as an example, Figure 1 and Figure 4 As shown, the operation performed when the digital signal is transmitted to the input end of the central module 1 includes: transmitting the reference signal 1 and the reference signal 2 to the correlator in the digital phase-locked amplifier unit 13 for correlation operation respectively; the correlation operation consists of a multiplier and a low-pass filter. If the digital signal is The effective part is The random noise mixed in is n(t); the reference signal 1 is The output signal after the multiplier is:

[0061] When V1 passes through a low-pass filter with a cutoff frequency of 2ω0, since the reference signal m2(t) is independent of the noise signal n(t), the output after the above signal integration is Similarly, since reference signal 2 is strictly orthogonal to reference signal 1, the output of reference signal 2 after passing through the correlator is Then, after arithmetic operation, the amplitude of the defect information of the object to be tested is In this way, the defect information of the object to be tested is obtained and the eddy current non-destructive testing is completed.

[0062] In summary, the present invention provides an eddy current nondestructive testing device, including: a central module, a digital-to-analog conversion module, a power amplifier module, an excitation coil, an acquisition module, a preamplifier module, an analog-to-digital conversion module and a display module, wherein: the digital-to-analog conversion module is connected to the output end of the central module, and converts the digitized excitation parameter signal output by the central module into an analog signal; the power amplifier module is connected to the output end of the digital-to-analog conversion module; the excitation coil is connected to the output end of the power amplifier module, generates an excitation signal, and performs excitation disturbance on the object to be tested, wherein the object to be tested generates an induction signal after the excitation disturbance; the acquisition module collects the induction signal; the preamplifier module is connected to the output end of the acquisition module; the analog-to-digital conversion module is connected to the output end of the preamplifier module, converts the preamplified induction signal into a digital signal and transmits it to the input end of the central module, and obtains the defect information of the object to be tested by performing calculation processing with the digitized excitation parameter signal; the display module is connected to the output end of the central module, and performs display control operations on the defect information. The eddy current nondestructive testing device of the present invention generates eddy current disturbances in the object to be tested through an excitation coil. The magnetic field generated by the eddy current disturbances is captured by the acquisition module and input into the digital phase-locked amplifier unit after pre-amplification and analog-to-digital conversion. After calculation, the defect information of the object to be tested is obtained. The operation is convenient and the results obtained are accurate and reliable. The eddy current nondestructive testing device of the present invention uses a central module to construct the digital phase-locked amplifier unit, which has a high system integration and reduces hardware costs. Therefore, the present invention effectively overcomes the various shortcomings of the existing technology and has high industrial utilization value.

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An eddy current nondestructive testing device, characterized in that: The eddy current nondestructive testing device at least includes: a central module, a digital-to-analog conversion module, a power amplifier module, an excitation coil, an acquisition module, a preamplifier module, an analog-to-digital conversion module and a display module, wherein: The digital-to-analog conversion module is connected to the output end of the central module and converts the digital excitation parameter signal output by the central module into an analog signal; The power amplifier module is connected to the output end of the digital-to-analog conversion module to amplify the analog signal; The excitation coil is connected to the output end of the power amplifier module to generate an excitation signal for exciting the object to be tested; The acquisition module acquires the induction signal generated by the object to be tested under the excitation disturbance; The preamplifier module is connected to the output end of the acquisition module to amplify the output signal of the acquisition module; The analog-to-digital conversion module is connected to the output end of the preamplifier module, converting the output signal of the preamplifier module into a digital signal and transmitting it to the input end of the hub module; The central module obtains defect information of the object to be tested based on the digital signal and the digitized excitation parameter signal; The display module is connected to the output end of the central module to display the defect information; The central module includes a control and communication unit, a signal generating unit and a digital phase-locked amplifier unit, wherein the control and communication unit receives the parameter instructions sent by the host computer and transmits the defect information and the display control signal to the display module; the signal generating unit generates the digital excitation parameter signal from the received parameter instructions, wherein the digital excitation parameter signal includes a reference signal 1 and a reference signal 2, and the reference signal 1 and the reference signal 2 have the same frequency and are strictly orthogonal; the digital phase-locked amplifier performs correlation and arithmetic operations on the digital signal; The digital lock-in amplifier unit includes a first correlator, a second correlator and an arithmetic operator, wherein: the first correlator receives the reference signal 1 and the digital signal; the second correlator receives the reference signal 2 and the digital signal; the arithmetic operator is connected to the output ends of the first correlator and the second correlator; The first correlator and the second correlator each include a multiplier and a low-pass filter, wherein: the multiplier in the first correlator receives the reference signal 1 and the digital signal, outputs the result to the low-pass filter in the first correlator after multiplication, and outputs the result to the arithmetic operator after filtering; the multiplier in the second correlator receives the reference signal 2 and the digital signal, outputs the result to the low-pass filter in the second correlator after multiplication, and outputs the result to the arithmetic operator after filtering; The acquisition module is a tunnel magnetoresistive sensor.

2. The eddy current nondestructive testing device according to claim 1, characterized in that: The central module is a field programmable logic gate array chip, a quantum processor chip, a dedicated integrated circuit chip, or a microprocessor chip.

3. The eddy current nondestructive testing device according to claim 1, characterized in that: The communication protocol of the control communication unit is RS-232 protocol, RS-422 protocol, RS-485 protocol or Bluetooth.

4. The eddy current nondestructive testing device according to claim 1, characterized in that: The signal generating unit is a direct digital frequency synthesizer.

5. The eddy current nondestructive testing device according to claim 1, characterized in that: The excitation coil is a planar double D-shaped excitation coil.

6. The eddy current nondestructive testing device according to claim 1, characterized in that: The number of the tunnel magnetoresistive sensors is N, where N is a natural number greater than or equal to 1.

7. The eddy current nondestructive testing device according to claim 6, characterized in that: The number of channels of the preamplifier module is N.

8. The eddy current nondestructive testing device according to claim 1, characterized in that: The display module is a display, a mobile phone, a tablet or a host computer.

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