Portable magnetic field imaging device and imaging method

Abstract

The invention discloses a portable magnetic field imaging device which comprises an array type magnetic field sensor, a sensor zooming mechanism, a multi-path differential output voltage signal processing circuit, a display screen, a magnetic field imaging model and the like. The array type magnetic field sensor can obtain magnetic field information of multiple points in a plane to be measured at the same time, magnetic field measurement in multiple planes is carried out through the sensor zooming mechanism, the magnetic field imaging model enables the magnetic field information to correspond to coordinates of a spatial position to be measured, and a magnetic field vector distribution diagram is drawn. The portable magnetic field imaging device disclosed by the invention can collect the magnetic field information of a plurality of measured points in the to-be-measured space at a high speed, and the imaging device is small in size and relatively good in portability.

Description

Technical Field

[0001] The invention relates to a portable magnetic field imaging device and an imaging method, belonging to the technical field of magnetic field measurement and imaging. Background Art

[0002] Aircraft, ships and spacecraft often work in complex environments such as high temperature, high pressure and high speed, which causes the ferromagnetic materials in their key components to be prone to defects such as cracks, indentations, tears, dents, burns and corrosion. Magnetic field imaging devices are often used for detection.

[0003] Existing magnetic field imaging devices mostly use a three-dimensional mechanical motion platform to drive a magnetic sensitive probe to perform three-dimensional scanning to obtain magnetic field data, and finally transmit the data to a computer to draw an image using Matlab software. This type of method can often only achieve single sensor probe detection, and the measurement points are sparse. The instrument has a single magnetic sensitive direction of the sensor, and the measurement points are sparse, so too many mechanical structures are required to achieve multi-point measurement in space, which makes it unportable, cumbersome to operate, slow to measure, and expensive.

[0004] Due to the above reasons, it is necessary to conduct in-depth research on the existing magnetic field imaging device to solve the above problems and realize the miniaturization of the magnetic field imaging device. Summary of the invention

[0005] In order to overcome the above problems, the inventors have conducted in-depth research and designed a portable magnetic field imaging device, including an array magnetic field sensor, a sensor zoom mechanism, a multi-channel differential output voltage signal processing circuit and a display screen. The sensor zoom mechanism is used to adjust the relative position between the array magnetic field sensor and the object to be measured, and the multi-channel differential output voltage signal processing circuit is used to convert the analog signal detected by the array magnetic field sensor into magnetic field digital information.

[0006] In a preferred embodiment, the magnetic field sensor includes a plurality of magnetically sensitive elements or devices arranged in an array, and can simultaneously obtain magnetic field information at multiple points in the plane to be measured.

[0007] In a preferred embodiment, the sensor zoom mechanism is a free telescopic mechanism. When zooming, the sensor zoom mechanism drives the array magnetic field sensor to move stepwise along a specified direction, and this movement changes the relative position between the array magnetic field sensor and the material to be measured, thereby quickly obtaining magnetic field information of multiple measured points in the measured space.

[0008] In a preferred embodiment, the array magnetic field sensor is detachably connected to the sensor zoom mechanism.

[0009] In a preferred embodiment, the multi-channel differential output voltage signal processing circuit includes a signal encoder (such as 74HC161 and LM324), a multiplexer (such as CD4067), an instrument amplifier (such as AD620), an A / D conversion circuit and a single-chip microcomputer (such as STM32F103), and the analog signals output by different magnetic sensitive elements or devices are encoded by the signal encoder.

[0010] The analog signals output by different magnetic sensitive elements or devices in the magnetic field sensor are obtained in sequence through the multi-way switching.

[0011] The instrument amplifier is used to amplify the voltage of the coded signal, and the A / D conversion circuit is used to convert the amplified coded signal into a digital signal.

[0012] The single chip microcomputer is used to control the signal processing circuit and perform magnetic field imaging so that the display screen can display the imaging results.

[0013] In a preferred embodiment, the single chip microcomputer extracts the digital level value from the magnetic field information matrix, converts it into magnetic field information, assigns the corresponding RGB color value, fills the corresponding color into the grid at the corresponding position of the display screen, and finally displays the measured magnetic field information on the display screen in the form of an image.

[0014] The present method also discloses a portable magnetic field imaging method, which is performed using the portable magnetic field imaging device, and comprises the following steps:

[0015] S1, zeroing the array magnetic field sensor;

[0016] S2, calibrating the linearity of the array magnetic field sensor;

[0017] S3. Measure the object to be measured, obtain magnetic field information, and display it on the display screen.

[0018] In a preferred embodiment, in S1, each magnetic sensitive element or device in the array magnetic field sensor is adjusted one by one. When the AD value of the magnetic sensitive element or device is within the range of 2048±10, no adjustment is required. When the detected AD value is greater than or less than the above range, it is marked at the corresponding position, for example, marked with "*", so as to set the correction deviation value to correct the magnetic sensitive element or device.

[0019] In a preferred embodiment, in S2, the array magnetic field sensor is taken out of the shell and placed in a magnetic field generator. The magnetic field generator generates a calibrated magnetic field. The detection results of each magnetic sensitive element or device are obtained respectively under the same calibrated magnetic induction intensity. The linearity of each magnetic sensitive element or device is calibrated according to the detection results, so that the magnetic sensitive element or device meets the linearity standard.

[0020] In a preferred embodiment, in S3, the relative position between the array magnetic field sensor and the object to be measured is changed by a sensor zoom mechanism to perform multi-plane magnetic field measurement to obtain magnetic field information of multiple measured points in the measured space.

[0021] The beneficial effects of the present invention include:

[0022] (1) In order to solve the problem of high-speed measurement of magnetic fields at multiple points in the measured space, the present invention adopts an array magnetic field sensor to simultaneously obtain magnetic field information at multiple points in the measured plane, and performs multi-plane measurement through a sensor zoom mechanism. The magnetic field information of multiple measured points in the measured space can be collected at high speed, and the imaging device is small in size and has good portability.

[0023] (2) To address the problem of multi-channel output voltage signal conditioning of array magnetic field sensors, the present invention combines a signal encoder, a multi-channel selection switch, an instrument amplifier, an A / D conversion circuit and a single-chip microcomputer to simplify the circuit structure and efficiently complete the signal digitization.

[0024] (3) The present invention constructs a magnetic field imaging model to correspond the magnetic field information to the coordinates of the space to be measured and converts the digital signal into magnetic field information, and finally displays the magnetic field information in the space to be measured in a visual form. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram showing the overall structure of a portable magnetic field imaging device according to a preferred embodiment of the present invention is shown;

[0026] Figure 2 A schematic diagram of zeroing an array magnetic field sensor of a portable magnetic field imaging device according to a preferred embodiment of the present invention is shown;

[0027] Figure 3 A schematic diagram of the magnetic field imaging result in Example 1 is shown.

[0028] Explanation of symbols:

[0029] 1-Array magnetic field sensor;

[0030] 2-Sensor zoom mechanism;

[0031] 3-Multi-channel differential output voltage signal processing circuit;

[0032] 4- Display screen;

[0033] 5- Shell. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below through the accompanying drawings and embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0035] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0036] The present invention provides a portable magnetic field imaging device, such as Figure 1 As shown, it includes an array magnetic field sensor 1, a sensor zoom mechanism 2, a multi-channel differential output voltage signal processing circuit 3 and a display screen 4.

[0037] The array magnetic field sensor 1 includes a plurality of magnetic sensitive elements or devices arranged in an array.

[0038] The array arrangement refers to a row arrangement of m×m or m×n magnetic sensitive elements or devices, preferably m×m magnetic sensitive elements or devices.

[0039] The magnetic sensitive element or device refers to a sensitive element or device whose characteristic parameters change significantly with the change of external magnetic quantity. Typical magnetic sensitive elements or devices include magnetic sensitive diodes, magnetic sensitive transistors and Hall sensors.

[0040] Traditional magnetic field imaging devices generally only use a single magnetic sensitive element or device for measurement. The measurement points are sparse, and the instrument requires too many mechanical structures to achieve spatial multi-position mobile measurement due to the single magnetic sensitivity direction of the sensor. This makes it inconvenient, cumbersome to operate, and slow to measure.

[0041] In the present invention, the magnetic field information of multiple points in the plane to be measured is obtained simultaneously by an array magnetic field sensor, so that the magnetic field information of multiple measured points in the plane to be measured can be collected at high speed, while reducing the spatial displacement mechanical structure, thereby achieving a reduction in the volume of the device.

[0042] The sensor zoom mechanism is used to adjust the relative position between the array magnetic field sensor and the object to be measured, so that the array magnetic field sensor can perform magnetic field measurement in multiple planes and obtain magnetic field information of multiple measured points in the measured space.

[0043] Preferably, the sensor zoom mechanism is a single-degree-of-freedom telescopic mechanism. More preferably, the sensor zoom mechanism can be telescoped perpendicular to the plane where the array-type magnetic field sensor is located.

[0044] Preferably, the number of magnetically sensitive elements or devices in the magnetic field sensor is m×m, and the magnetic field measurement is performed in n planes to be measured through the sensor zoom mechanism, so that the magnetic field information of multiple measured points in the measured space can be collected at high speed to complete the magnetic field measurement in the measured space.

[0045] Preferably, the sensor zoom mechanism is a stepping screw, which drives the array magnetic field sensor to move stepwise in a specified direction through the rotation of the stepping motor when zooming. This movement changes the relative position between the array magnetic field sensor and the material to be tested, thereby quickly obtaining spatial magnetic field data on the surface or near the surface of the object to be tested.

[0046] The multi-channel differential output voltage signal processing circuit is used to convert the analog signal detected by the array magnetic field sensor into magnetic field digital information.

[0047] According to the present invention, the output signal of the array magnetic field sensor is a differential voltage signal, and the number of outputs is m×m×n×3.

[0048] Preferably, the signal processing circuit includes a signal encoder, a multi-way selection switch, an instrument amplifier, an A / D conversion circuit and a single-chip microcomputer, etc.

[0049] The analog signals output by different magnetic sensitive elements or devices are encoded by the signal encoder.

[0050] The analog signals output by different magnetic sensitive elements or devices in the array magnetic field sensor are obtained in sequence through the multi-way switching.

[0051] The instrument amplifier is used to amplify the voltage of the coded signal, and the A / D conversion circuit is used to convert the amplified coded signal into a digital signal.

[0052] The single-chip microcomputer is used to control the signal processing circuit and perform magnetic field imaging. When a signal for starting to collect magnetic field information is received, a reset signal is first sent to the CLR port, and then a pulse square wave is sent to the counter. Each time a square wave is sent, a magnetic field sensor is selected, and the digital quantity sent by the A / D conversion circuit is read and stored in the magnetic field information matrix corresponding to the plane coordinates to be measured. By judging the level state of RCO after the 16th pulse is sent, the array collection information is terminated or the counter is reset and the magnetic field information is collected again, thereby forming a closed-loop system to achieve the correspondence between the magnetic field information and the spatial position coordinates.

[0053] Preferably, the signal encoder adopts 74HC161 and LM324, the multi-way selection switch adopts CD4067, the instrument amplifier adopts AD620, and the single chip microcomputer adopts STM32F103.

[0054] The display screen is used to display the detection results.

[0055] Preferably, the magnetic field information is presented in a graphical form.

[0056] More preferably, the magnetic field information is converted into color information and displayed in the form of an image.

[0057] Specifically, the single chip microcomputer extracts the digital level value from the magnetic field information matrix, converts it into magnetic field information, assigns the corresponding RGB color value, fills the corresponding color into the grid at the corresponding position of the display screen, and finally displays the measured magnetic field information on the display screen in the form of an image.

[0058] In a preferred embodiment, the array-type magnetic field sensor is detachably connected to the sensor zoom mechanism, so as to facilitate linearity calibration of the array-type magnetic field sensor.

[0059] In a preferred embodiment, the portable magnetic field imaging device also has a battery, making the device more portable.

[0060] According to the present invention, the portable magnetic field imaging device has a housing 5 for fixing the array magnetic field sensor, the sensor zoom mechanism, the multi-channel differential output voltage signal processing circuit and the display screen.

[0061] The present invention also discloses a portable magnetic field imaging method, which is performed using the portable magnetic field imaging device, and comprises the following steps:

[0062] S1, zeroing the array magnetic field sensor;

[0063] S2, calibrating the linearity of the array magnetic field sensor;

[0064] S3. Measure the object to be measured, obtain magnetic field information, and display it on the display screen.

[0065] In S1, each magnetic sensitive element or device in the array magnetic field sensor is adjusted one by one. When the AD value of the magnetic sensitive element or device is within the range of 2048±10, no adjustment is required. When the detected AD value is greater than or less than the above range, a mark is made at the corresponding position, such as a mark of "*", such as Figure 2 As shown, the correction deviation value is set to calibrate the magnetic sensitive element or device.

[0066] In S2, the array magnetic field sensor is taken out from the shell and placed in a magnetic field generator (such as CH-100). The magnetic field generator generates a calibrated magnetic field. The detection results of each magnetic sensitive element or device are obtained under the same calibrated magnetic induction intensity. The linearity of each magnetic sensitive element or device is calibrated according to the detection results, so that the magnetic sensitive element or device meets the linearity standard.

[0067] In S3, the relative position between the array magnetic field sensor and the object to be measured is changed by the sensor zoom mechanism, and the magnetic field measurement in multiple planes is performed to obtain the magnetic field information of multiple measured points in the measured space.

[0068] During each measurement process, when a signal to start collecting magnetic field information is received, a reset signal is first sent to the CLR port of the microcontroller, and then a pulse square wave is sent to the microcontroller counter. Each time a square wave is sent, a magnetic field sensor is selected, and the digital quantity sent by the A / D conversion circuit is read and stored in the magnetic field information matrix corresponding to the plane coordinates to be measured. By judging the level state of RCO after the 16th pulse is sent, the array information collection is terminated or the counter is reset and the magnetic field information is collected again, thereby forming a closed-loop system to achieve the correspondence between the magnetic field information and the spatial position coordinates.

[0069] Furthermore, the digital level value is extracted from the magnetic field information matrix by the single chip microcomputer, converted into magnetic field information, the corresponding RGB color value is assigned, the corresponding color is filled into the grid at the corresponding position of the display screen, and finally the measured magnetic field information is displayed on the display screen in the form of an image.

[0070] Example

[0071] Example 1

[0072] A portable magnetic field imaging device is used to detect a fixed magnetic field of 100 mT. The portable magnetic field imaging device includes an array magnetic field sensor, a sensor zoom mechanism, a multi-channel differential output voltage signal processing circuit, a display screen and a magnetic field imaging model. The array magnetic field sensor includes 4×4 Hall sensors arranged in an array.

[0073] The output signal of the array magnetic field sensor is a differential voltage signal, and the number is 4×4 outputs.

[0074] The multi-channel differential output voltage signal processing circuit comprises a signal encoder, a multi-channel selection switch, an instrument amplifier, an A / D conversion circuit and a single chip microcomputer.

[0075] The signal encoder adopts 74HC161 and LM324, the multi-way selection switch adopts CD4067, the instrument amplifier adopts AD620, and the single-chip microcomputer adopts STM32F103.

[0076] The magnetic field imaging results are as follows Figure 3As shown, the measurement data of all sensors on the array magnetic field sensor chip are displayed on the left side of the display screen, where the maximum magnetic field measurement is 103.7mT, the minimum is 96.6mT, the average magnetic field measurement is 99.58125mT, and the maximum error with the fixed magnetic field value (100mT) is 0.925%, that is, the magnetic field measurement accuracy of the instrument is ±0.4mT.

[0077] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front", "rear", etc. indicate positions or positional relationships based on the working state of the present invention, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", and "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0078] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] The present invention has been described above in conjunction with preferred embodiments, but these embodiments are only exemplary and serve only as an illustration. On this basis, the present invention may be subjected to a variety of substitutions and improvements, all of which fall within the scope of protection of the present invention.

Claims

1. A portable magnetic field imaging device, characterized in that: It includes an array magnetic field sensor, a sensor zoom mechanism, a multi-channel differential output voltage signal processing circuit and a display screen. The sensor zoom mechanism is used to adjust the relative position between the array magnetic field sensor and the object to be measured. The magnetic field sensor is detachably connected to the sensor zoom mechanism, The multi-channel differential output voltage signal processing circuit is used to convert the analog signal detected by the array magnetic field sensor into magnetic field digital information.

2. The portable magnetic field imaging device according to claim 1, characterized in that: The array magnetic field sensor is composed of m×m magnetic sensitive elements or devices arranged in an array.

3. The portable magnetic field imaging device according to claim 1, characterized in that: The sensor zoom mechanism is a free telescopic mechanism. The array magnetic field sensor can perform magnetic field measurement in n planes to be measured through the sensor zoom mechanism, and collect magnetic field information of multiple measured points in the measured space.

4. The portable magnetic field imaging device according to claim 1, characterized in that: The multi-channel differential output voltage signal processing circuit includes a signal encoder, a multi-channel selection switch, an instrument amplifier, an A / D conversion circuit and a single-chip microcomputer. The analog signals output by different magnetic sensitive elements or devices are encoded by the signal encoder. The analog signals output by different magnetic sensitive elements or devices in the array magnetic field sensor are obtained in sequence through the multi-way switching. The instrument amplifier is used to amplify the voltage of the coded signal, and the A / D conversion circuit is used to convert the amplified coded signal into a digital signal. The single chip microcomputer is used to control the signal processing circuit and perform magnetic field imaging so that the display screen can display the imaging results.

5. The portable magnetic field imaging device according to claim 1, characterized in that: The single chip microcomputer performs coordinate mapping and converts the digital signal into magnetic field information, converts the magnetic field information into color information, and finally displays it in the form of an image through a display screen.

6. A portable magnetic field imaging method, characterized in that: The method is carried out using the portable magnetic field imaging device as claimed in any one of claims 1 to 5, comprising the following steps: S1, zeroing the array magnetic field sensor; S2, calibrating the linearity of the array magnetic field sensor; S3. Measure the object to be measured, obtain magnetic field information, and display it on the display screen.

7. The portable magnetic field imaging method according to claim 6, characterized in that: In S2, the array magnetic field sensor is taken out from the shell and placed in a magnetic field generator. The magnetic field generator generates a calibrated magnetic field. The detection results of each magnetic sensitive element or device are obtained respectively under the same calibrated magnetic induction intensity. The linearity of each magnetic sensitive element or device is calibrated according to the detection results, so that the magnetic sensitive element or device meets the linearity standard.

8. The portable magnetic field imaging method according to claim 6, characterized in that: In S3, the relative position between the array magnetic field sensor and the object to be measured is changed by the sensor zoom mechanism, and the magnetic field measurement in multiple planes is performed to obtain the magnetic field information of multiple measured points in the measured space.

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