KR101734003B1

KR101734003B1 - Apparatus and Method for Detecting the Defects of Far Side using Magnetic Sensor

Info

Publication number: KR101734003B1
Application number: KR1020150189117A
Authority: KR
Inventors: 이진이; 김정민; 김세진; 심순보
Original assignee: 대한민국(국방부 공군참모총장)
Priority date: 2015-12-30
Filing date: 2015-12-30
Publication date: 2017-05-11

Abstract

The present invention relates to a device for detecting a dihedral defect and a method thereof. According to the present invention, a magnetic field which is optimized for detecting a dihedral defect is applied to conduct a detection in order to estimate the position, and orientation of the dihedral defect with high precision. Also, since the structure is conveniently applied to a curved object, a lift-off can be minimized even when the shape of the object changes. Data can be extracted by removing the distortion noise or error of the magnetic field detected upon the dihedral defect, thus leading to the obtainment of accurate dihedral defect data. The device for detecting a dihedral according to an embodiment of the present invention comprises a magnetizer which generates a magnetic field upon the application of an alternating current, and applies the magnetic field to a portion of an object being measured to magnetize the same while arranging a portion of an opposite surface of a dihedral defect of the object along a single direction to magnetize the same, a scan unit including magnetic sensors arranged at a predetermined interval, while generating an output signal corresponding to the intensity of an induced current generated by the magnetization of a portion of the object using sensors which are arranged in a row parallel to the same direction as the portion of the object arranged by magnetization, a data processor electrically which is connected to the scan unit to receive the output signal, a monitor for displaying the result analyzed by the data processor, and a control unit including a power supply for supplying power to the scan unit, data processor, and monitor. The magnetizer includes a yoke having a tapered end, and a coil winded to the yoke to be applied with an alternating current. The magnetizer can magnetize a portion of the object being measured along a single direction for the magnetization.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backside defect inspection apparatus and method using a magnetic sensor,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back surface defect inspection apparatus and method for detecting a back surface defect of an object to be measured by using a magnetic sensor. More specifically, a magnetic field is applied from a surface of a measured object to detect a defect occurring inside the measured object, and a distortion of a magnetic field around a defect generated due to the applied magnetic field is detected, And more particularly, to a backside defect inspection apparatus and method for detecting defects.

The contents described in this section merely provide background information on the embodiment of the present invention and do not constitute the prior art.

The power or propulsion of machinery such as airplanes or spacecrafts is frequently exposed to high temperature and high pressure environments during operation, and continuous monitoring of power or propulsion is essential for stable operation.

Particularly, spot welding of a jet engine, which provides powerful propulsion for high-speed operation of an air vehicle, is likely to cause multisite fatigue crack due to continuous operation in a high temperature and high pressure environment, The presence and progress of defects should be checked periodically to prevent accidents caused by element breakage or cutting.

On the other hand, backside defects occurring inside the spot welding area can be detected through non-destructive inspection such as ultrasonic inspection or magnetic inspection. However, when the spot welding is performed on a small machine element such as a bracket, There is no suitable flaw detection method for measuring defects.

In addition, in the conventional nondestructive inspection method using a magnetic field at the time of defect detection, it is difficult to apply a magnetic field suitable for a backside defect, and there is a disadvantage that noise or an error occurs during defect inspection and it is difficult to detect an exact back defect.

In order to solve such a problem, the present invention has a magnetizer for applying a magnetic field suitable for a back surface defect, detects a magnetic field distortion around a defect caused by an applied magnetic field by a magnetic sensor, and processes sensed information to process noise or error And to obtain defect information on the removed side.

A backside defect inspection apparatus according to an embodiment of the present invention generates a magnetic field when an alternating current is applied and magnetizes the magnetic field by applying a magnetic field to a part of the object to be measured, And n sensors arranged in a line so as to be parallel to one direction aligned with magnetization of a part of the object to be measured and magnetized in a part of the object to be measured, A data processor electrically connected to the scan unit and the scan unit including a magnetic sensor for generating a corresponding output signal and receiving an output signal and analyzing an output signal to detect a backside defect; And a controller unit including a power supply for supplying power to the scan unit, the data processor, and the monitor, The magnetizing device may include a yoke having a tapered end and a coil wound around the yoke and receiving an alternating current so that a part of the measured object is magnetized in one direction.

The case includes a case having a lower portion including a scan portion and a portion of which is opened to expose the magnetic sensor to the outside, a guide member guiding movement of the scan portion to reciprocate the scan portion to both sides of the case, , And a head portion including a drive motor for providing power for reciprocating along the guide body to both sides of the scan portion case.

The controller unit may further include a controller that receives an input signal applied by a user and generates an operation signal for operating or stopping the drive motor and applies the generated operation signal to the drive motor.

In addition, the lower surface of the case may be provided in a shape complementary to the measurement surface shape of the measured object so as to be in contact with the measurement surface of the measured object.

In addition, the lower surface of the case may be formed of a bakelite material.

The controller unit includes a filtering circuit that is electrically connected to the scan unit to receive and filter the output signal generated by the magnetic sensor, an amplifying circuit that amplifies the filtered output signal, and an RMS (Root-Mean -Square), and an AD conversion circuit for converting the RMS-converted output signal into an analog signal, so that the output signal converted by the signal conversion circuit may be input to the data processor .

In addition, a touch screen, which is electrically connected to the controller unit and has an interface capable of operating the driving motor by transmitting an input signal to the controller and displaying the detected defect information analyzed by the data processor, And a fixing belt fixedly supporting the screen holder on one surface thereof and adapted to support a load of the touch screen and the screen holder by being wound around a part of the user's body.

In addition, the fastening belt may be provided to support the load by being wrapped around the user's waist or pelvis.

A backside defect inspection method according to an embodiment of the present invention includes an information reception step of receiving scan information generated by scanning a surface of a magnetized subject with a magnetic sensor and signal conversion of the received scan information, , Generating an information generating step of generating at least one defect information file based on the converted back side defect information, and generating the generated defect information file according to a user's selection and outputting the defect information file to the display device An information extracting step of extracting a back side defect area by signal processing the back side defect information displayed on the display device, and a defect displaying step of displaying the back side defect information through the information extracting step on a display device have.

In addition, the information conversion step includes a filtering step for extracting only a specific band of the scan information, an amplification step for amplifying the scanned information through the filtering step, and a root-mean-square (RMS) An AD conversion step of AD (analog to digital) conversion of the scan information through the RMS conversion step and the RMS conversion step, and converting the scan information into the back side defect information.

The information display step may be a display of at least one of a contour graph or a waterfall graph of the background defect information displayed by calling the defect information file.

Also, the information extracting step may include a defect extracting step of generating a cross-sectional surface distribution (B-scan) of the surface defect information displayed on the display device and removing a region excluding a preset maximum area and a minimum area of the cross- . &Lt; / RTI >

In addition, the information extracting step may include a step of generating a histogram of the back side defect information displayed on the display device, and a step of improving the signal to noise ratio to remove the set maximum and minimum areas of the histogram.

According to an embodiment of the present invention, the application and detection of a magnetic field optimized for the detection of the backside defect can be performed to estimate the position, direction, etc. of the backside defect with high accuracy.

In addition, it is possible to minimize the lift-off of the object to be measured by changing the shape of the measured object by providing a structure that is easy to apply to the object to be measured on the curved surface.

In addition, since noise or error of the magnetic field distortion detected for the back side defect can be removed and data can be extracted, accurate back side defect data can be obtained.

1 is a conceptual diagram illustrating a backside defect inspection apparatus according to an embodiment of the present invention.
2 is a conceptual diagram illustrating a signal conversion circuit of a back side defect inspection apparatus according to an embodiment of the present invention.
3 is a conceptual diagram illustrating a structure and operation principle of a scan unit according to an embodiment of the present invention.
4 is an enlarged perspective view showing a part of components of a back side defect inspection apparatus according to an embodiment of the present invention.
Fig. 5 is an enlarged perspective view showing other components mounted with the components of Fig. 4;
FIG. 6 is a state diagram illustrating a state in which some components of a backside defect inspection apparatus according to an embodiment of the present invention are applied.
FIG. 7 is a state diagram illustrating a state in which some components of a backside defect inspection apparatus according to another embodiment of the present invention are applied.
8 is a side view of a controller of a backside defect inspection apparatus according to an embodiment of the present invention.
FIG. 9 is a state diagram illustrating some components of a backside defect inspection apparatus according to an embodiment of the present invention.
10 is a flowchart illustrating a method of detecting a backside defect according to an embodiment of the present invention.
11 shows an example of a method in which a result of a back surface defect inspection method according to an embodiment of the present invention is written on a display device.
12 is a conceptual diagram for explaining an information extracting step of the back side defect inspection method according to an embodiment of the present invention.
FIG. 13 shows an example in which the information extracting step of FIG. 12 is applied.

Hereinafter, some embodiments of the present invention will be described in detail based on exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals whenever possible, even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 1 is a conceptual view illustrating a backside defect inspection apparatus according to an embodiment of the present invention. Referring to FIG. 1, a backside defect inspection apparatus will be schematically described.

The scan unit 100 includes a magnetic encoder 101 and a magnetic sensor 111 and generates a signal corresponding to the intensity of the induced current induced by magnetizing the measured object 10.

The head unit 200 includes a case 201, a guide body 203, and a driving motor 205, and provides a space in which the scanning unit 100 can be installed inside.

The controller unit 300 includes a signal conversion circuit 301, a data processor 303, a controller 305, a power supply 307 and a monitor 309. The controller 300 analyzes and analyzes signals detected by the scan unit 100, Processes it, displays it, and supplies power to the device.

The information on the back side defect processed in the controller unit 300 may be transmitted to the touch screen 401 and displayed on the touch screen 401. The touch screen 401 is connected to the controller 305 for controlling the driving motor 205 And an interface for transmitting an input signal.

2 is a conceptual diagram illustrating a signal conversion circuit of a back side defect inspection apparatus according to an embodiment of the present invention.

The signal conversion circuit 301 is a circuit that receives the output signal generated by the magnetic sensor 111 of the scan unit 100 and performs signal conversion and transmits the signal to the data processor 303. The signal conversion circuit 301 is constituted by a filtering circuit 311, an amplification circuit 313, an RMS conversion circuit 315 and an AD conversion circuit 317.

The magnetic field of the surface is distorted due to the presence of the side defects 20 and the magnetic sensor 111 is magnetized by applying the magnetic field in the magnetic encoder 101 of the scan unit 100, Generates an output signal corresponding to the distortion (magnetic flux change) of the magnetic field and inputs it to the signal conversion circuit 301. At this time, since the magnetic sensor 111 may be composed of n sensors as described later, the number of output signals input to the signal conversion circuit 301 may be n according to the number of sensors.

The output signal of the magnetic sensor 111 is subjected to high-pass filtering in the filtering circuit 311 and amplified by an amplifying circuit 313. The amplified output signal is subjected to RMS conversion (Root Mean Square Transform) in the RMS converting circuit 315, Which is again subjected to analog-to-digital conversion by the AD conversion circuit 317 and input to the data processor 303. The filtering circuit 311, the amplifying circuit 313, the RMS converting circuit 315 and the AD converting circuit 317 provided in the signal converting circuit 301 are mounted on one PCB to minimize the communication line of the signal converting process It is possible to do.

3 is a conceptual diagram illustrating a structure and operation principle of a scan unit according to an embodiment of the present invention.

The magnetic field generator 101 includes a yoke 103 and a coil 105 wound around the yoke 103. When an alternating current is applied to the coil 105, a magnetic field is generated in the yoke 103, Is applied to a part of the measured object (10) and magnetized. The magnetizer 101 aligns a portion of the opposite side of the surface defect 20 of the measured object 10, that is, a portion of the surface in one direction, which can be achieved by the shape of the yoke 103.

The yoke 103 is formed in a bar shape in which a part is curved, and both end portions are tapered to minimize the leakage magnetic flux at both ends. When a magnetic field is generated as AC current is applied to the coil 105 wound on the outer surface of the yoke 103, at both ends of the tapered yoke 103, as shown in FIG. 3, A magnetic field can be applied to the body 10 and a part of the surface on the opposite side of the back surface defect 20 of the measured object 10 can be magnetized in the direction of the magnetic force line of the generated magnetic field as shown in Fig. In this case, the magnetic force lines of FIG. 3 exemplify one of the magnetic field lines of the generated magnetic field. The yoke 103 may be made of a material having a high permeability such as an electric steel sheet (SiFe) to generate an induced current in the measured object 10 more favorably.

The magnetic sensors 111 are arranged at regular intervals with n sensors, and a part of the surface of the measured object 10 may be arranged in a line parallel to the aligned direction of magnetization. The sensor constituting the magnetic sensor 111 may be a Hall sensor or a magnetoresistive sensor and may be a magnetic sensor having a magnetic field of a surface of the measured object 10 in the normal direction of the surface of the measured object 10, Detects distortion.

FIG. 4 is an enlarged perspective view illustrating a part of components of the backside defect inspection apparatus according to one embodiment of the present invention, and FIG. 5 is an enlarged perspective view showing other components mounted with the components of FIG.

The magnetic encoder 101 and the magnetic sensor 111 are integrated to constitute the scan unit 100 and the integrated magnetizer 101 and the magnetic sensor 111 may be provided in separate housings.

The head unit 200 includes a case 201 including the scan unit 100 therein, a guide member 203 for providing a path along which the scan unit 100 moves, and a drive motor 205 for moving the scan unit 100 ).

The case 201 has a lower surface including a scan unit 100 and a part of which is opened so that the magnetic sensor 111 of the scan unit 100 is exposed to the outside. The case 201 may be formed of an anodized aluminum material, and in particular, a lower surface of the case 201 may be formed of a Bakelite material. The lower side of the Bakelite material has a relative permittivity (

) And the electric conductivity (?) Are low, it is possible to reduce the influence on the magnetic field distortion of the surface of the measured object 10 which may occur when the lower surface of the case 201 contacts the measured object 10.

The guide member 203 guides the movement of the scan unit 100 so that the scan unit 100 reciprocates in both sides of the case 201 from inside the case 201. The guide body 203 may be provided in a bar shape between both sides of the case 201 and may be provided in two or more bar shapes to provide a stable supporting force.

The driving motor 205 is connected to a part of the scan unit 100 and the guide unit 203 is inserted into the hollow hole formed in the inner side of the scan unit 100 to guide the scan unit 100 to both sides of the guide 201 To provide reciprocating motive power. A motor (not shown) and a driving wheel (not shown) connected to the motor shaft provide rotational force to the outer surface of the guide body 203 inside the drive motor 205 to provide power to the guide body 203 But may be provided in other forms suitable for providing power.

FIG. 6 is a state diagram illustrating a state in which some components of a backside defect inspection apparatus according to an embodiment of the present invention are applied. FIG. 7 is a view illustrating a state in which some components of a backside defect inspection apparatus according to another embodiment of the present invention are applied Fig.

The lower surface of the case 201 may be formed so as to be in contact with the measurement surface of the measured object 10 in a shape complementary to the measured surface shape of the measured object 10. In this case, when the measurement surface of the measured object 10 is formed as a curved surface, the lower surface of the case 201 may be formed into a curved surface that is complementary to the measured surface shape of the measured object 10 as shown in FIG. If the case 201 is formed as a curved surface, the distance between the scan unit 100 and the measured object 10 is reduced to minimize the lift-off even though the measured surface of the measured object 10 is curved The distortion of the magnetic field can be measured with high sensitivity while reducing the error.

8 is a side view showing a back surface defect inspection apparatus according to an embodiment of the present invention.

The controller unit 300 includes a signal conversion circuit 301, a data processor 303, a controller 305, a power supply 307 and a monitor 309 in a rack case with a lower wheel As shown in FIG.

The data processor 303 is electrically connected to the scan unit 100 to receive an output signal, and analyzes the output signal to detect the backside defect 20. When the output signal of the scan unit 100 is converted by the signal conversion circuit 301, the data processor 303 may receive the converted information from the signal conversion circuit 301. [

The controller 305 receives an input signal applied by a user and generates an operation signal for operating or stopping the drive motor 205 and applies the generated operation signal to the drive motor 205. A user may input an input signal to the controller 305 by using a device such as a button or by operating or stopping the driving motor 205 through the interface of the touch screen 401. [

The power supply 307 generates an electric current to supply AC current to the magnetizing apparatus 101 and supplies power to the data processor 303, the controller 305 and a monitor 309 to be described later. The power supply 307 may vary the frequency of the alternating current according to the depth or shape of the back surface defect 20 of the measured object 10 and supply it to the magnetizer 101. For example, when the backside defect 20 is relatively less grown and deep from the surface of the measuring object 10, the power supply 307 supplies a lower low frequency It is also possible to vary the alternating current to apply it to the magnetizer 101.

The monitor 309 may be a folding monitor that displays the analyzed result in the data processor 303 and may be stored in a rack case of the controller unit 300. [ The user takes out the monitor 309 stored in the rack case of the controller unit 300 to check the result of the measurement of the back surface defect 20 of the measured object 10 and outputs the result analyzed in the data processor 303 . The monitor 309 may be equipped with a touch screen to apply an operation signal to the data processor 303 in order to process the measurement result into more useful data.

FIG. 9 is a state diagram illustrating some components of a backside defect inspection apparatus according to an embodiment of the present invention.

The touch screen 401 is electrically connected to the controller unit 300 and displays defect information analyzed and analyzed by the data processor 303 and transmits an input signal to the controller 305 to operate the drive motor 205 Lt; / RTI > The touch screen 401 is electrically connected to the controller unit 300. The touch screen 401 and the controller unit 300 transmit and receive data and data through a cable, It can be in the form of. The touch screen 401 can transmit the input signal to the controller 305 to operate the driving motor 205. However, in order to process the result of displaying the defect information analyzed and analyzed by the data processor 303 into more useful data An operation signal for operating the processor 303 may be applied to the data processor 303. [

The screen mount 403 provides a mounting force capable of supporting the touch screen 401. The screen mount 403 may be formed as a multi-joint fixing device capable of changing the position of the touch screen 401 in a user-friendly manner.

The fixing belt 405 receives and supports the screen holder 403 on one side and is provided to support the load of the touch screen 401 and the screen holder 403 by being wound around a part of the user's body. The body part of the user to which the fastening belt 405 is wound may be the user's waist or pelvis. The fixing belt 405 may be one in which the one end and the other end are made of a hook and loop of a hook and loop and is fixed to the user's body. However, the fixing belt 405 can be used regardless of a specific shape, It is obvious.

FIG. 10 is a flow chart of a method of detecting a back side defect according to an embodiment of the present invention, and FIG. 11 shows an example of a method of displaying results of a back side defect inspection method according to an embodiment of the present invention in a display device.

In the information receiving step (S110), the surface of the magnetized object (10) is scanned by the magnetic sensor (111), and the generated scan information is received. The scan information refers to information generated by the magnetic sensor 111 in accordance with the magnetic field distortion of the surface of the measured object 10 magnetized by the magnetizing device 101. [

In the information conversion step (S120), the received scan information is converted into the back surface defect information of the measured object (10). The defect information refers to information for visually confirming the surface defect 20 by converting the scan information.

The information conversion step S120 includes a filtering step S121 for extracting a specific band of the scan information, an amplification step S123 for amplifying the filtered scan information, an RMS conversion step for obtaining an RMS value from the amplified scan information, (S125), and an A / D conversion step (S127) for A / D-converting the RMS value, whereby the scan information can be converted into the back side defect information. The information conversion step (S120) may be performed by the signal conversion circuit 301.

In the information generation step S130, at least one defect information file is generated based on the converted back side defect information. The subject 10 to be magnetized by the magnetizing device 101 may have a plurality of the subject 10 itself or a plurality of measurement areas of the subject 10 to generate a plurality of pieces of scan information , And in the information generation step (S130), one or more defect information files are generated by distinguishing the plurality of scan information.

In the information display step (S140), at least one of the generated defect information files is called according to the user's selection and displayed on the display device. The display device may be a device equipped with a display unit such as a monitor 309 or a touch screen 401 provided in the controller unit 300. Information displayed on the display unit may be displayed on the rear side Contour graph or waterfall graph of defect information. Here, the contour graph represents a graph representing the degree of the magnetic field distortion of the background defect information by a color change, and the waterfall graph represents a graph representing the waveform of the magnetic field distortion of the surface defect information by arranging the waveform on a specific axis . In the information display step S140, a plurality of defect information files may be called at one time to represent a plurality of contour graphs or waterfall graphs.

12 is a conceptual diagram for explaining an information extracting step of the back side defect inspection method according to an embodiment of the present invention.

In the information extracting step S150, the back side defect information displayed on the display device is signal-processed to extract the back side defect area. More specifically, when it is necessary to remove unspecific errors or noises of the back side defect information displayed on the display device, the step of improving the signal to noise ratio (S151) is performed, and when the measurement data around the back side defect area is to be removed, The extraction step S153 is performed.

In the signal-to-noise ratio enhancement step S151, a histogram of the electromagnetic field distribution of the back surface defect information displayed on the display device is generated (Fig. 12 (A)), and four vertical cursors Select the maximum and minimum areas. In this case, since the maximum area of the histogram means an unspecified error and the minimum area means noise, information on the back side defect area from which unspecified errors and noise are removed can be obtained by removing the maximum area and the minimum area of the selected histogram. The signal-to-noise ratio enhancement step (S151) may be expressed as a signal / noise ratio enhancement step.

In the defect extracting step S153, a specific area of the back side defect information displayed on the display device is selected by a cross-shaped cursor that is programmed and displayed in advance to generate a cross section distribution (B-scan) ). In the generated cross-sectional distribution (B-scan), the four horizontal cursors previously programmed and displayed are moved to select the maximum and minimum areas of the cross-sectional distribution (B-scan). At this time, the maximum area of the cross-sectional distribution (B-scan) represents the center of the defect, and the minimum area represents the tip of the defect. Since the defect 20 is located between the tip portions of the defect, if the portion excluding the maximum region and the minimum region of the cross-sectional distribution (B-scan) is removed, only the center portion and the tip portion of the defect are indicated, Can be obtained.

FIG. 13 shows an example in which the information extracting step of FIG. 12 is applied.

In the defect display step S160, the back side defect information after the information extraction step S150 is displayed on the display device. The information displayed in the defect display step S160 may be two kinds of information processed by the signal-to-noise ratio improving step S151 or the defect extracting step S153, and both the steps S151 and S153 Information indicating that the center and the tip of the defect are marked and at the same time, the unspecified error or noise is removed. At this time, a cruciform selection cursor for confirming the details of the displayed defect information may be applied to the display device.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

10: object to be measured 20: surface defect
100: scan unit 101:
103: yoke 105: coil
111: magnetic sensor 200:
201: Case 203: Guide body
205: driving motor 300:
301: Signal conversion circuit 303: Data processor
305: Controller 307: Power supply
309: Monitor 311: Filtering circuit
313: Amplification circuit 315: RMS conversion circuit
317: AD conversion circuit 401: Touch screen
403: Screen holder 405: Fixing belt

Claims

A magnetizer for generating a magnetic field when an alternating current is applied and magnetizing the magnetic field by applying the magnetic field to a part of the object to be measured while aligning a part of the surface on the opposite side of the back surface defect of the object to be measured in one direction, A magnetic sensor for generating an output signal corresponding to an intensity of an induced current generated by magnetization in a part of the measured object with n sensors arranged in a line so that a part of the measured object is magnetized and aligned in parallel with one direction aligned A scan unit including a scan unit;
A data processor electrically connected to the scan unit and receiving the output signal and analyzing the output signal to detect the backside defect; a monitor for displaying a result analyzed by the data processor; A controller unit including a processor and a power supply for supplying power to the monitor; And
A casing having the scan unit therein and having a bottom surface with a portion thereof opened to expose the magnetic sensor to the outside; and a guide unit for guiding the movement of the scan unit such that the scan unit moves reciprocally to both sides of the case, And a head motor including a driving motor for providing a power for reciprocating the scanning unit along the guide body to both sides of the case,
Wherein the controller further comprises a controller for receiving an input signal applied by a user and generating an operation signal for operating or stopping the drive motor and applying the generated operation signal to the drive motor,
The lower surface of the case is provided so as to be in a shape complementary to the measurement surface shape of the measured object and to be in contact with the measurement surface of the measured object,
Wherein the magnetizer includes a yoke having a tapered end portion and a coil wound around the yoke and receiving an alternating current so as to magnetize a part of the measured object in one direction and generate at the yoke due to an alternating current applied to the coil Wherein a leak magnetic flux of the magnetic field is minimized at the tapered end of the yoke.

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The method according to claim 1,
Wherein a bottom surface of the case is formed of a bakelite material.

6. The apparatus of claim 5, wherein the controller
A filtering circuit that is electrically connected to the scan unit and receives and filters an output signal generated by the magnetic sensor; an amplifying circuit that amplifies the filtered output signal; and a RMS (Root-Mean-Square ), And an AD conversion circuit for converting the RMS-converted output signal into an A / D conversion circuit, wherein the output signal converted by the signal conversion circuit is input to the data processor A defect inspection system.

The method according to claim 6,
A touch screen electrically connected to the controller unit and having an interface capable of displaying defect information analyzed and analyzed by the data processor and transmitting an input signal to the controller to operate the drive motor;
A screen mount for providing a mounting force for supporting the touch screen; And
And a fixing belt fixedly supporting the screen mount on one surface thereof and wound around a part of the user's body to support a load of the touch screen and the screen mount.

8. The method of claim 7,
Wherein the fixing belt is wound around the waist or the pelvis of the user to support a load.

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