JP2008032575A - Eddy current measuring probe and flaw detection device using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eddy current measuring probe capable of performing thickness reduction inspection or the like unaccompanied by a supplementary work such as dismantling of a heat insulating material, and evaluating easily a flaw of a pipe or the like, and a flaw detection device using the probe. <P>SOLUTION: The eddy current measuring probe 1 is arranged in the state of keeping a prescribed distance to an electric conductor or a ferromagnetic material which is a measuring object 2, and is equipped with an excitation part 3 for generating an eddy current in the measuring object. The excitation part 3 is constituted of the first excitation coil 5 and the second excitation coil 4 arranged adjacently to the first excitation coil 5, in order to form a magnetic field distribution concentrated into the measuring object 2. The probe 1 may be equipped with a magnetic field detection part 6 disposed adjacently to the excitation part 3. Hereby, flaw detection of a flaw section generated on a ferromagnetic pipe covered with the heat insulating material can be performed accurately and nondestructively in a short time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an eddy current measuring probe that can be used for flaw detection of a flawed part of a pipe covered with a heat insulating material such as a heat insulating pipe, and a flaw detection apparatus using the probe.

  Many heat insulation pipes exist in power plants such as chemical plants and thermal power plants, and failures caused by thinning damage to the pipes are considered to be serious. In recent years, the occurrence of outer surface corrosion under a heat insulating material has become a problem, and it has become necessary to detect or repair an outer surface thinning portion. As an inspection method for the outer wall thinning, it is effective to perform the inspection by directly removing the heat insulating material, but it takes a great amount of labor and cost to detach the heat insulating material and to set the related scaffolding. Therefore, it is necessary to identify the location where the thinning occurs and minimize the location where the heat insulating material is removed.

  As an inspection method currently performed, the above-described visual inspection, neutron moisture meter (presence / absence of moisture in the heat insulating material), and a test method using radiation are known. It is difficult to identify the location of occurrence by a visual inspection or a test method using a neutron moisture meter. On the other hand, although inspection using radiation is an effective inspection method, there are problems with the speed and safety of inspection.

  Since maintenance inspection of pipes requires inspection from the inside of the pipe, an eddy current (Eddy Current Testing) flaw detection method is practically used as a crack inspection method. In the eddy current flaw detection method, a probe comprising an excitation coil and a detection coil driven by an AC power source arranged at a predetermined interval is inserted into a steel pipe made of electrical wiring, conductors, or ferromagnetic material, and the steel pipe is damaged. This is a nondestructive inspection method in which a change in magnetic flux is detected by a detection coil (see Patent Document 1).

JP 2001-145225 A

  When the method of disposing an excitation coil outside a steel pipe or the like as in Patent Document 1 is applied to a damage inspection of a steel pipe covered with a heat insulating material, there is a distance between the excitation coil and the steel pipe. As a result, the distribution of the eddy current generated from the exciting coil to the steel pipe is widened, and the strength is reduced, so that it is difficult to detect the presence of thinning in the steel pipe.

  In view of the above problems, the present invention enables a thinning inspection and the like that does not involve incidental construction such as dismantling of a heat insulating material while continuing operation, and can easily evaluate scratches on piping and the like. An object of the present invention is to provide a simple eddy current measuring probe and a flaw detection apparatus using the probe.

In order to achieve the above object, an eddy current measuring probe according to the present invention is an exciter that is disposed at a predetermined distance from a conductor or a ferromagnetic material that is an object to be measured and generates an eddy current in the object to be measured. A first excitation coil and a second excitation coil disposed adjacent to the first excitation coil so that the excitation unit forms a magnetic field distribution concentrated on the object to be measured; It is characterized by comprising.
The eddy current measurement probe of the present invention preferably includes a magnetic field detection unit disposed adjacent to the excitation unit, and the magnetic field detection unit eddies from the object to be measured induced by the magnetic field generated by the excitation unit. It consists of a detection coil or a magnetic detection element for detecting current.
Preferably, the first and second excitation coils and the detection coil have a structure in which they are concentrically arranged adjacent to each other.
The magnetic field detector is preferably configured to detect magnetic fields in different directions or obtain a differential output.

  According to the above configuration, the first excitation coil and the second excitation coil are excited by flowing currents in opposite directions, so that the conductive or ferromagnetic material arranged away from the eddy current measurement probe can be used. An eddy current measurement localized on the surface of the object to be measured can be generated.

In the above configuration, the eddy current measurement probe preferably includes a magnetizer.
According to the eddy current measurement probe of the present invention, when the piping inside the heat insulation pipe having the exterior material made of a magnetic material is flawed by the eddy current measurement probe, the exterior material is magnetized by the magnetizer, Has the effect of facilitating the penetration of eddy currents into the internal piping of the heat insulation piping. For this reason, in the eddy current measurement using the eddy current measurement probe, when the magnetic noise is large, the magnetic noise can be reduced by providing a magnetizer.

The flaw detection apparatus using the eddy current measurement probe according to the present invention is arranged with a predetermined distance from a conductor or a ferromagnetic material to be measured, and an excitation unit that generates eddy current in the measurement object and excitation. An eddy current measurement probe comprising a magnetic field detection unit disposed adjacent to the excitation unit, an excitation unit drive source of the eddy current measurement probe, and a signal processing unit of the eddy current measurement probe. Comprises a first excitation coil and a second excitation coil disposed adjacent to the first excitation coil in order to form a magnetic field distribution concentrated on the object to be measured. It is characterized by comprising a detection coil or a magnetic detection element for detecting eddy currents from an object to be measured induced by a magnetic field generated in an excitation unit.
According to the above configuration, the eddy current localized on the surface of the object to be measured made of a conductive or ferromagnetic material arranged away from the eddy current measurement probe is generated, and the damaged part of the object to be measured of this eddy current is generated. Changes in can be detected. Therefore, a flawed part of a pipe covered with a heat insulating material such as a heat insulating pipe can be detected accurately in a short time without being broken.

  In the above configuration, the excitation unit driving source preferably generates an alternating current or a pulse. Therefore, the eddy current change in the damaged part of the object to be measured can be detected with high sensitivity.

  According to the eddy current measuring probe and the flaw detection apparatus using the eddy current measuring probe of the present invention, it is effective for measurement when the distance between the eddy current measuring probe and the object to be measured is long, and in particular, covered with a heat insulating material or the like. It is possible to detect flaws in the conductive or ferromagnetic pipes that have been made in a short time and with high accuracy.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding members are denoted by the same reference numerals.
First, an eddy current measurement probe according to the present invention will be described.
1A and 1B are schematic views showing the configuration of an eddy current measurement probe according to the present invention, in which FIG. 1A is an external view in which a current measurement probe is installed on a heat insulation pipe, and FIG. 1B is an AA shown in FIG. Sectional drawing which follows a line, (C) has shown sectional drawing which follows the BB line shown to (A) of the probe for eddy current measurement.
As shown in FIG. 1 (A), the eddy current measurement probe 1 of the present invention is arranged with a predetermined distance held on a conductor 2A or a ferromagnetic body of a heat insulation pipe as a measurement object 2. An excitation unit 3 for generating an eddy current in the measurement object 2 is provided. In order to form a magnetic field distribution concentrated on the DUT 2, the excitation unit 3 includes a first excitation coil 5 and a second excitation coil 4 disposed adjacent to the first excitation coil 5. , Is composed of. As shown in FIG. 1 (B), the heat insulation pipe 2 is composed of a pipe 2A made of a conductor or a ferromagnetic material, a heat insulation material 2B, and an exterior material 2C that protects the heat insulation material 2B.

  The eddy current measurement probe 1 may include a magnetic field detection unit 6 disposed adjacent to the excitation unit 3. The magnetic field detection unit 6 can be configured by a detection coil or a magnetic detection element that detects eddy currents from the DUT 2 induced by the magnetic field generated by the excitation unit 3. In the illustrated case, a detection coil is used as the magnetic field detection unit 6.

  As shown in FIGS. 1A and 1C, the eddy current measurement probe 1 includes a second excitation coil 4, a first excitation coil 5, and a detection coil 6 arranged from the outside to the inside. It consists of and. The first and second exciting coils 5 and 4 and the detection coil 6 are arranged concentrically, and their shapes are circular. As long as these coils 4, 5, and 6 are concentric, they may be oval, elliptical, or polygonal.

  As shown in FIG. 1A, a current flows in the opposite direction to the terminals 4A and 4B of the second exciting coil 4 and the terminals 5A and 5B of the first exciting coil 5, and the resultant magnetic field is The eddy current measuring probe is concentrated in the center direction. In the eddy current measurement probe 1, the magnetic field generated by the inner first excitation coil 5 is controlled using the magnetic field generated by the outer second excitation coil 4. Distribution.

  The magnetomotive force in each of the first and second exciting coils 5 and 4 may be determined in order to obtain an optimum magnetic distribution. A mechanism capable of changing the ratio of magnetomotive force in the first and second exciting coils 5 and 4 may be provided.

This magnetomotive force ratio can be fundamentally designed by numerical analysis.
FIG. 2 is a distribution diagram of eddy currents due to magnetic fields generated from the first excitation coil 5 and the second excitation coil 4, and FIG. 3 shows a single excitation coil for comparison with FIG. It is an eddy current distribution map. Eddy current distribution was analyzed using finite element method. Each figure shows a cross-sectional view around the left axis of the figure.
FIG. 2 shows a cross section of the flat plate 10 made of the first and second exciting coils 5 and 4 and the conductor 2A or the ferromagnetic material to be measured. The distance between the first and second exciting coils 5 and 4 and the flat plate 10 is L. In this arrangement, the first and second exciting coils 5 and 4 were excited by flowing currents in opposite directions. The magnetomotive force ratio was set to the first excitation coil 5: second excitation coil 4 = 1: 2. In this case, it can be seen that in the eddy current distribution 12 generated in the flat plate 10, a local eddy current 12 </ b> A is obtained at a position substantially corresponding to the first exciting coil 5.
On the other hand, as shown in FIG. 3, the eddy current distribution 14 when the single excitation coil 13 is excited by flowing a current has a small peak intensity 14 </ b> A and deviates from a position facing the excitation coil 13. It can be seen that the distribution becomes wider. For this reason, the resolution | decomposability in the flaw detection of the security piping mentioned later also falls.
From this, in the eddy current measurement probe according to the present invention, current flows through the first and second exciting coils 5 and 4 in opposite directions, and the magnetomotive force ratio is adjusted, so that As described above, even when the heat insulating material 2B has a distance from the pipe 2A, a local eddy current 12A can be generated in the pipe 2A immediately below the first and second exciting coils 5 and 4.

  The detection coil 6 may be a single type, a differential type, or a multi type. In the case of the differential type, as shown in FIG. 1C, two detection coils 6A and 6B can be used. By detecting the differential outputs of the two coils 6A and 6B wound in the same phase, magnetic field detection by eddy current can be measured with high sensitivity. In order to obtain a differential output, the detection coil 6 may connect two coils 6A and 6B wound in opposite phases to each other in series.

  When a magnetic detection element is used as the magnetic field detection unit 6 instead of a detection coil, any of a Hall effect element, a magnetoresistive element, a giant magnetoresistive element, a ferromagnetic application element, and a SQUID can be used. Similarly to the detection coil 6, the magnetic detection element is preferably configured to detect a magnetic field in a different direction or obtain a differential output.

A modification of the eddy current measurement probe according to the present invention will be described.
FIG. 4 is a cross-sectional view showing the configuration of a modified example of the eddy current measurement probe according to the present invention. As shown in FIG. 4, the eddy current measurement probe 15 is different from the eddy current measurement probe 1 in that it further includes a magnetizer 16 that covers the eddy current measurement probe 1. The magnetizer 16 can be composed of a coil, a permanent magnet, or the like. The magnetizer 16 magnetizes the exterior material 2C when the exterior material 2C of the heat insulation pipe 2 is made of a magnetic material such as an iron plate, and the magnetic field generated by the excitation unit 3 of the eddy current measurement probe 1 is inside the heat insulation pipe 2. It has the effect of facilitating the penetration of eddy currents into the pipe 2A. Further, in the eddy current measurement described later, the magnetic noise includes magnetic noise generated in the pipe to be measured. When the magnetic noise is large, the magnetic noise can be reduced by the action of the magnetizer 16. If this magnetizer is used in combination, it is not limited to eddy current measurement in which the distance between the eddy current measurement probe and the object to be measured (this distance is appropriately referred to as lift-off) as in the heat insulation pipe described later, It can also be used in small eddy current measurements. In this case, since the eddy current distribution is also controlled, the eddy current distribution generated in the object to be flawed can be controlled, so that the flaw detection resolution can be improved.

Next, the flaw detection apparatus 20 using the eddy current measurement probe of the present invention will be described.
FIG. 5 is a block diagram showing a configuration of the flaw detection apparatus 20 using the eddy current measurement probes 1 and 15 of the present invention. The flaw detection device 20 using the eddy current measurement probes 1 and 15 processes the output signals from the excitation unit drive source 21 and the magnetic field detection unit 6 for driving the excitation unit 3 of the eddy current measurement probes 1 and 15. And a signal processing unit 22.
The exciter drive source 21 generates an oscillator 23 that generates a sufficient output for driving the first and second exciting coils 5 and 4 of the exciter 3, and amplifies the output of the oscillator 23 as necessary. An oscillator amplifier 24 is included. The oscillator 23 can generate a continuous wave or a pulse.
In addition, when using the eddy current measurement probe 15 having the magnetizer 16, a DC power source for the magnetizer 16 may be further provided. Since the other points are the same as those of the eddy current measurement probe 1, the following description will be made assuming that the eddy current measurement probe 1 is used.

  The signal processing unit 22 detects the output signal 6C from the magnetic field detection unit, converts the analog signal into a digital signal, and processes the digitized signal to determine an eddy current. And comprising. In order to detect a scratch on the DUT 2 with high sensitivity, an amplifier (not shown) may be inserted in front of the A / D converter 25. This amplifier may be incorporated in the eddy current measurement probe 1. The processor 26 can be a computer.

  When the output from the oscillator 23 is a continuous wave, the penetration frequency of eddy current generated in the device under test 2 is calculated as the frequency, and a frequency that can generate eddy current in the device under test 2 may be selected.

  When the output from the oscillator 23 is a pulse, a pulse wave including a frequency capable of generating an eddy current calculated in the case of a continuous wave may be used. In this case, the output signal from the magnetic field detector 6 may be detected by the signal processor 22 on the time axis. In the signal processing unit 22, the output signal from the magnetic field detection unit 6 may be Fourier transformed to detect a frequency component related to the eddy current of the pulse to be applied.

  When the excitation unit drive source 21 is composed of a power source that generates alternating current or pulses, it is possible to detect the eddy current change in the damaged portion of the DUT 2 with higher sensitivity than when the excitation unit 3 is driven with direct current. Can do.

Here, the eddy current measuring probe 1 can be mounted on a probe driving device such as a self-propelled robot provided with a carriage having a moving mechanism by a battery-driven motor. Further, the eddy current measurement probe 1 may include a plurality of excitation units 3 and magnetic field detection units 6 so that multiple points can be measured at a time.
In the determination of the scratches on the flat plate at a distance from the pipe 2A in the heat insulation pipe or the eddy current measuring probe 1, the eddy current data on the normal heat insulation pipe or flat plate having no scratch is separately used as calibration data. Can be used.

  When the magnetic field detector 6 is not provided in the eddy current measurement probe 1, the first excitation coil 5 and / or the second excitation coil 4 of the excitation unit 3 can be used as a detection coil. In this case, the signal processing unit 20 includes an impedance measurement unit, measures the impedance of the first excitation coil 5 and / or the second excitation coil 4 itself, and an eddy current flows through the DUT 2. The eddy current can be measured by measuring the impedance change.

  According to the flaw detection apparatus 20 using the eddy current measurement probe 1 of the present invention, the eddy current measurement probe 1 generates eddy currents locally in a pipe separated by a heat insulation material such as a heat insulation pipe, thereby improving the resolution. Can be improved. For this reason, the damaged part of 2 A of pipes covered with the heat insulating material 2B like the heat insulating pipe 2 can be detected accurately in a short time without being broken.

Hereinafter, the present invention will be described in more detail with reference to examples.
As Example 1, an eddy current measurement probe 1 will be described. The eddy current measuring probe 1 is a circular plate coil in which the first and second exciting coils 5 and 4 and the detection coil 6 are arranged in close contact in order from the outside to the inside. The magnetomotive force ratio was set to the first excitation coil 5: second excitation coil 4 = 1: 2. The configuration of each coil is shown below.
First exciting coil 5: The outer diameter and inner diameter were 70 mm and 50 mm, the width was 5 mm, and the number of turns was 200.
Second exciting coil 4: The outer diameter and inner diameter were 90 mm and 70 mm, the width was 5 mm, and the number of turns was 100.
Detection coil 6: A differential detection coil in which the outer diameter and the inner diameter are 50 mm and 40 mm, the width is 5 mm, the number of turns is 100, and two coils 6A and 6B are used and connected in a differential manner.

  As Example 2, a flaw detection apparatus 20 using the eddy current measurement probe 1 of Example 1 was manufactured. The flaw detection apparatus 20 has the configuration shown in FIG. 5, and the excitation unit drive source 23 is a function synthesizer (manufactured by NF Circuit Design Block Co., Ltd., model 1940) and an oscillator amplifier 24 (NF circuit design, Inc.). Model HSA4011) made by Bloc was used. The output signal 6C from the detection coil 6 was detected by a lock-in amplifier (manufactured by NF Circuit Design Block Co., Ltd., model LI5640). A signal from the oscillator 23 was used as a reference signal for the lock-in amplifier. The excitation frequency of the first and second exciting coils 5 and 4 of the eddy current measuring probe 1 calculates the penetration depth of eddy current generated in the pipe 2A of the heat insulation pipe described later, and eddy current is generated in the pipe 2A. A numerical value that can be used was selected to be a continuous wave (CW) of 200 Hz. The signal processing unit 22 converts the output signal 6C from the detection coil 6 into a digital signal by the A / D converter 25, and inputs the signal to the personal computer 26 as the processing device 26. The operating position of the eddy current measuring probe 1 is set to a distance from the pipe 2A, that is, the lift-off is 50 mm in consideration of the thickness of the heat insulating material 2B.

A measurement result by the flaw detection apparatus 20 using the eddy current measurement probe 1 described in the first embodiment and the second embodiment will be described.
FIG. 6 is a plan view showing a state in which a flaw is intentionally formed on the flat plate sample 10 to be measured. The flat plate sample is made of an iron plate having a thickness of 5 mm and has a size of 850 mm × 850 mm. The size of each scratch was two types of 50 mm × 50 mm and 30 mm × 30 mm, and the depth of the scratch was 3.8 mm, 2.5 mm, and 1.5 mm in order from the left side to the right side of FIG.

  The probe 1 for eddy current measurement is scanned in the AA direction in FIG. 5 on the center line of the scratch having the same size while maintaining the distance from the flat plate sample 10 at 50 mm, and the width 80 cm is 20 seconds. Scanned. In this case, the scanning speed is 4 cm / min.

FIG. 7 is a diagram showing an eddy current measurement result of a flat plate sample in which a flaw is intentionally formed by the flaw detection apparatus 20 using the eddy current measurement probe of Example 2, and the case where the flaw size is 50 mm × 50 mm. Show. In FIG. 7, the horizontal axis indicates the movement distance (mm), and the movement distance is 800 mm. The vertical axis in FIG. 7 indicates the X and Y signals (mV) obtained by detecting the signal from the detection coil with a lock-in amplifier.
As is clear from FIG. 7, since the X signal has a positive peak and the Y signal has a negative peak signal, the signal in the portion surrounded by the dotted ellipse is 50 mm. It can be seen that in the eddy current measurement probe 1 having lift-off, a flaw intentionally provided on the flat plate sample can be detected.

  FIG. 8 is a diagram showing an eddy current measurement result of a flat plate sample intentionally formed with a flaw detector using the eddy current measurement probe of Example 2, where the size of the flaw is 30 mm × 30 mm. Show. The horizontal and vertical axes in the figure are the same as those in FIG. The moving distance on the horizontal axis is 800 mm. As is apparent from FIG. 8, since the X signal has a positive peak and the Y signal has a negative peak signal, the signal in the portion surrounded by the dotted ellipse is 50 mm. It can be seen that in the eddy current measurement probe 1 having lift-off, a flaw intentionally provided on the flat plate sample can be detected.

Next, a description will be given of measurement results obtained by detecting flaws in the heat insulation pipe by the flaw detection apparatus 20 using the eddy current measurement probe 1 of Example 2.
As the structure of the heat insulating pipe 2, the outer side of the steel pipe 2A having an outer diameter of 115 mm and a wall thickness of 6.5 mm is covered with a heat insulating material 2B having a thickness of about 50 mm. The exterior material 2C is coated with a magnetic material such as tin having a thickness of 0.75 mm. The steel pipe 2A of the heat insulation pipe 2 was intentionally damaged.
FIG. 9 is a schematic view of a heat insulation pipe 2A that is intentionally scratched and partially thinned. As shown in FIG. 9, a pipe that is ground with a width of 30 mm in a direction perpendicular to the axial direction of the pipe 2 </ b> A and intentionally provided with a scratch 2 </ b> D is shown. Here, the maximum depth in the grinding direction of the pipe 2A is referred to as a thinning depth. In this case, the thinning amount of the scratch 2D was adjusted by changing the thinning depth, and was set to 25%, 50%, and 75% at the three locations shown from the top to the bottom in FIG.

FIG. 10 is a diagram showing an eddy current measurement result of a heat retaining pipe having a pipe with a partial thickness reduction, and shows a case where the thickness reduction is 3 mm. In the figure, the horizontal axis represents time (seconds), and the vertical axis represents X and Y signals (mV) obtained by detecting a signal from the detection coil with a lock-in amplifier.
As is clear from FIG. 10, since the X signal has a plus-side peak and the Y signal has a minus-side peak signal, the portion of the signal surrounded by the dotted ellipse has a heat retention pipe. It turns out that the damage | wound of the partial thinning pipe | tube inside can be detected.

  According to the flaw detection apparatus 20 using the eddy current measurement probe 1 of the present invention shown in the first and second embodiments, both detect eddy currents caused by flaws in the heat retaining pipe 2 intentionally provided with flaws. I was able to.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. For example, in the present embodiment, the shape of the object to be measured has been described for the case of a tube or a plate, but it is possible to design a probe according to the shape of the object to be measured, the thickness of the material, the relative permeability, etc. Needless to say, it is also included in the scope of the present invention to appropriately design and use the signal processing unit depending on whether the signal from the signal is a continuous wave or a pulse.

It is a schematic diagram which shows the structure of the probe for eddy current measurement which concerns on this invention, (A) is the external view which installed the probe for eddy current measurement in heat insulation piping, (B) is the AA line shown to (A). Sectional drawing which follows, (C) is sectional drawing which follows the BB line shown to (A) of the probe for eddy current measurement. It is an eddy current distribution map by the magnetic field generated from the first exciting coil and the second exciting coil. FIG. 3 is a distribution diagram of eddy currents generated from a single exciting coil shown for comparison with FIG. 2. It is sectional drawing which shows the structure of the modification of the probe for eddy current measurement which concerns on this invention. It is a block diagram which shows the structure of the flaw detection apparatus using the probe 1 for eddy current measurement of this invention. It is a top view which shows the state which formed the damage | wound intentionally in the flat plate sample used as a to-be-measured object. It is a figure which shows the eddy current measurement result of the flat plate sample which formed the flaw intentionally with the flaw detector using the probe for eddy current measurement of Example 2. FIG. It is a figure which shows the eddy current measurement result of the flat plate sample which formed the flaw intentionally with the flaw detector using the probe for eddy current measurement of Example 2, and has shown the case where the magnitude | size of a flaw is 30 mm x 30 mm. It is a schematic diagram of a heat insulation pipe intentionally scratched and partially thinned It is a figure which shows the eddy current measurement result of the heat retention piping which has the pipe | tube with which partial thinning was carried out, and has shown the case where the thickness reduction is 3 mm.

Explanation of symbols

1, 15: Probe for eddy current measurement 2: Object to be measured (thermal insulation pipe)
2A: Conductor or ferromagnetic material (pipe)
2B: Thermal insulation material 2C: Exterior material 3: Excitation section 4: Second excitation coil 4A, 4B: Terminal 5: First excitation coil 5A, 5B: Terminal 6: Magnetic field detection section (detection coil)
6A, 6B: Differential coil 6C: Output signal 10: Flat plate 12, 14: Eddy current distribution 12A: Local eddy current 13: Single excitation coil 14A: Peak intensity 16: Magnetizer 20: For eddy current measurement Flaw detection device 21 using probe: excitation unit drive source 22: signal processing unit 23: oscillator 24: oscillator amplifier 25: A / D converter 26: processing device

Claims (7)

A conductor or a ferromagnetic material to be measured is arranged with a predetermined distance, and includes an excitation unit that generates an eddy current in the measured object.
The excitation unit includes a first excitation coil and a second excitation coil disposed adjacent to the first excitation coil to form a magnetic field distribution concentrated on the object to be measured. A probe for measuring eddy currents.   A detection coil or magnetic detection unit that includes a magnetic field detection unit disposed adjacent to the excitation unit, the magnetic field detection unit detecting an eddy current from the measurement object induced by a magnetic field generated by the excitation unit; The probe for eddy current measurement according to claim 1, comprising an element.   3. The eddy current measurement probe according to claim 2, wherein the first and second exciting coils and the detection coil have a structure in which they are concentrically adjacent to each other.   The eddy current measurement probe according to claim 2, wherein the magnetic field detection unit is configured to detect a magnetic field in a different direction or to obtain a differential output.   The eddy current measurement probe according to claim 1, wherein the eddy current measurement probe includes a magnetizer. An excitation unit that is disposed at a predetermined distance from a conductor or a ferromagnetic material that is an object to be measured and generates an electric current in the object to be measured; and a magnetic field detection unit that is disposed adjacent to the excitation unit An eddy current measuring probe comprising:
An excitation drive source of the eddy current measurement probe;
A signal processing unit of the eddy current measurement probe,
The excitation unit includes a first excitation coil and a second excitation coil disposed adjacent to the first excitation coil to form a magnetic field distribution concentrated on the object to be measured;
An eddy current measurement probe is used, wherein the magnetic field detection unit comprises a detection coil or a magnetic detection element that detects an eddy current from the measurement object induced by the magnetic field generated by the excitation unit. Flaw detection equipment.   The flaw detection apparatus using an eddy current measurement probe according to claim 6, wherein the excitation unit drive source generates an alternating current or a pulse.