JP4865343B2 - Inspection method for iron-based structures - Google Patents

Description

  The present invention relates to a ferrous structure inspection method and a magneto-impedance effect sensor used in the inspection method, and detects defects in ferrous structures such as the case of a transformer on a pillar and the inner surface of a steel pipe, the position of a reinforcing bar in a concrete building, and the like. Useful to do.

As an amorphous alloy wire, an amorphous alloy wire having zero magnetostriction or negative magnetostriction has been developed, which has an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are separated by a domain wall. Yes.
The inductance voltage component in the output voltage between both ends of the wire generated when a high frequency current is applied to the zero magnetostrictive or negative magnetostrictive amorphous magnetic wire is easily increased in the circumferential direction by the circumferential magnetic flux generated in the cross section of the wire. It occurs due to the magnetized outer shell being magnetized in the circumferential direction. Accordingly, the circumferential magnetic permeability μθ depends on the circumferential magnetization of the outer shell.
Therefore, when an external magnetic field is applied to the energized amorphous wire, the magnetic flux acting on the outer shell portion having the easily magnetizable property in the circumferential direction is obtained by synthesizing the circumferential magnetic flux and the external magnetic flux by the energization. Is deviated from the circumferential direction and magnetization in the circumferential direction is less likely to occur, the circumferential permeability μθ is changed, and the inductance voltage is changed.
Thus, this fluctuation phenomenon is called a magnetic inductance effect, and an amorphous wire or the like that exhibits this effect is called a magnetic inductance effect element.

Further, when the frequency of the energization current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμθ) ^1/2 (μθ is the circumferential permeability, as described above, and ρ is (The electrical resistivity, w indicates the angular frequency, respectively) varies with μθ, and this μθ varies with the external magnetic field as described above, so that the resistance voltage component in the output voltage across the wire also varies with the external magnetic field. Become.
Thus, this fluctuation phenomenon is called a magnetoimpedance effect, and an amorphous wire or the like that exhibits this effect is called a magnetoimpedance effect element.

  Therefore, an external magnetic field detection method using the magneto-impedance effect element (see, for example, Patent Document 1) and an external magnetic field detection method using the magnetic inductance effect (see, for example, Patent Document 2) have been proposed.

  In the above, the positive and negative of the external magnetic field causes the circumferential shift φ of the magnetic field to be positive or negative, but the reduction factor cos (± φ) of the circumferential magnetic field does not change. Does not change. Accordingly, the external magnetic field-output characteristics are substantially symmetrical with respect to the y axis as shown in FIG. 7A described later when the magnetic field is taken on the x axis and the output is taken on the y axis. Further, as shown in FIG. 7A, it is known that the nonlinearity occurs.

As shown in FIG. 8A, the magnetic field detection circuit using the magneto-impedance effect element basically includes (1) a high-frequency power source 2 ′ for applying a high-frequency excitation current to the magneto-impedance effect element 1 ′, 2) a magneto-impedance effect element 1 ′, (3) a detection circuit 3 ′ that demodulates a modulated wave obtained by modulating the high-frequency excitation current (carrier wave) with an external magnetic field Hex applied to the magneto-impedance effect element, and (4) a demodulated wave. Is composed of an amplifier 4 ′ and (5) a detected magnetic field display unit 5 ′.
8B, (b) shows the detected magnetic field Hex applied to the magneto-impedance effect element, (b) shows the high-frequency excitation current wave (carrier wave) Ic flowing through the magneto-impedance effect element, and (c) shows the magneto-impedance effect. The modulated wave as the output of the element, (d) shows the envelope waveform of the modulated wave, and (e) shows the demodulated wave. 8F shows the output V of the amplifier, and the output Eout shown in FIG. 7C described later is in the range of + Vcc to 0 and −Vcc to 0 with respect to the power supply voltages + Vcc and −Vcc of the amplifier. The level is adjusted so that it fits in

The relationship between the amplitude Hex of the magnetic field to be detected and the amplitude of the output V can be expressed as shown in FIG.
Therefore, in the circuit of FIG. 8A, the negative feedback coil indicated by 6 ′ is subjected to negative feedback to linearize the characteristics as shown in FIG.
Further, as shown in (c) of FIG. 7, the characteristic of (b) of FIG. 7 is moved in the direction of the arrow by the bias magnetic field as shown in (c) of FIG. It is also possible to determine the polarity by placing ~ + Hmax within the range of one oblique line region Δw ′.

Conventionally, it is known to detect a defect in a steel sheet by a leakage magnetic flux flaw detection method using a magnetic impedance effect sensor (Non-Patent Document 1).
However, in this defect detection method, it is necessary to apply a magnetic flux to the object to be inspected, and the inspection object is limited in applying the magnetic flux.
In FIG. 8-2 (f), it is often observed that the reference level is shifted due to variations in magneto-impedance effect elements and other circuit components. For this reason, conventionally, a volume is connected to the offset adjustment terminal of the operational amplifier, and the reference level is adjusted by the volume.
Further, in order to adjust the output of the operational amplifier with respect to variations in the characteristics of the magneto-impedance effect element, an electronic volume is connected to the offset adjustment terminal of the amplifier, and correction data is input in accordance with the variation. It is also known to adjust the output of an operational amplifier by operating a volume (Patent Document 3).
However, when detecting defects such as flaws, thinning, rust, etc. in iron-based structures by scanning with a sensor, changes in temperature conditions and fluctuations in stray capacitance along the scanning route can be achieved with any of the above-mentioned amplifier output adjustments. As a result, a shift from the reference level occurs later, and it is difficult to perform accurate detection.

JP 7-181239 A JP-A-6-283344 Paragraphs 0046 and 0047 of JP 2002-198582 A Koji Fujimoto, Yoshio Mohri, MAG-98-86, p39-43

  An object of the present invention is to provide a method capable of accurately and easily inspecting an iron-based structure with a magneto-impedance effect sensor and a magneto-impedance effect sensor suitable for the method. For example, a case of a transformer on a column, a steel pipe It can be applied to the deterioration diagnosis of the inner wall of the steel or the rebar inside the concrete structure.

According to a first aspect of the present invention, there is provided a method for inspecting an iron-based structure comprising: a magnetic impedance effect sensor including a bias magnetic field coil attached to a magneto-impedance effect element; While applying an exciting current to the element and applying a bias magnetic field in which the AC component is superimposed on the DC component, the element travels along the iron-based structure. During this travel, the bias magnetic field is applied to the iron-based structure and the iron-based structure is connected to the magnetic circuit. The detection output is changed by changing a bias magnetic field passing through the magneto-impedance effect element based on the defect of the iron-based structure that is passed as a part of the iron-based structure, and the defect of the iron-based structure is detected from this change. .
  According to a second aspect of the present invention, there is provided a method for inspecting an iron-based structure, wherein a bias magnetic field coil is attached to a magneto-impedance effect element, an output of the element is amplified by an amplifier, and a detection output is obtained. A compensation signal for canceling the offset is generated, and a magneto-impedance effect sensor provided with a correction circuit for applying the compensation signal to the amplifier as an input for erasing the offset is provided. An excitation current is applied to the magneto-impedance effect element. While energizing and running along a ferrous structure while applying a bias magnetic field in which the ac component is superimposed on the dc component, during this run, the bias magnetic field passes through the ferrous structure and passes the ferrous structure as part of the magnetic circuit. The detection output is changed by changing the bias magnetic field passing through the magneto-impedance effect element based on the defect of the iron-based structure. And detecting defects in iron-based structure from the change.
  According to a third aspect of the present invention, there is provided a method for inspecting an iron-based structure, wherein a bias magnetic field coil is attached to each of a pair of magneto-impedance effect elements, and the output of both elements is amplified by a differential amplifier to obtain a detection output. A magneto-impedance effect sensor provided with a correction circuit for generating a compensation signal for canceling the offset using the offset of the amplifier output as an input signal and applying the compensation signal to the amplifier as an input for erasing the offset While applying an exciting current to the impedance effect element and applying a bias magnetic field in which the AC component is superimposed on the DC component, the impedance effect element is run along the iron-based structure. During this travel, the bias magnetic field is applied to the iron-based structure and the iron-based structure is moved. The detection is performed by changing the bias magnetic field passing through the magneto-impedance effect element based on the defect of the iron-based structure that is passed as part of the magnetic circuit. Changing the output, and detecting a defect of the iron-based structure from this change.
  According to a fourth aspect of the present invention, there is provided a method for inspecting an iron-based structure, wherein a bias magnetic field coil is attached to each of a pair of magneto-impedance effect elements, and the output of both elements is amplified by a differential amplifier to obtain a detection output. A correction signal for canceling the offset is generated between the input terminals of the amplifier using the offset of the differential amplifier output as an input signal, and this compensation signal is applied to the amplifier as an input for eliminating the offset. A magneto-impedance effect sensor provided with a circuit is driven along an iron-based structure while applying a bias magnetic field in which an alternating current component is superimposed on a direct current component while applying an exciting current to the magneto-impedance effect element. Pass the iron-based structure through the magnetic structure as part of the magnetic circuit and pass through the magneto-impedance effect element based on the defect of the iron-based structure. Changing the astigmatic magnetic field changing the detection output, and detecting a defect of the iron-based structure from this change.
  An inspection method for an iron-based structure according to claim 5 is the method for inspecting an iron-based structure according to any one of claims 2 to 4, wherein an offset of an amplifier or a differential amplifier output is predetermined in the correction circuit of the magneto-impedance effect sensor. Means are provided for generating a compensation output when the value is reached.
  An inspection method for an iron-based structure according to a sixth aspect is the method for inspecting an iron-based structure according to the fifth aspect, wherein an offset of an output of a magneto-impedance effect sensor or a differential amplifier is multiplied by n (n> 1). A means for inputting to the correction circuit is provided.

(1) In the method for inspecting an iron-based structure according to the present invention, the iron-based structure also becomes a part of a magnetic circuit with respect to a bias magnetic field, and the strength of the bias magnetic field causes damage, corrosion, or thinning of the iron-based structure. Varies depending on the degree. Since this bias magnetic field passes through the amorphous wire as the magneto-impedance effect element in the axial direction, the circumferential magnetic field due to the excitation current is shifted from the circumferential direction, and the degree of the shift is corrosion / thinning of the embedded iron-based material. It changes according to the degree. Therefore, the change in output of the magneto-impedance effect element correlates with the degree of scratches, corrosion, and thinning of the iron-based structure, and the degree of defects in the iron-based structure can be inspected from the change in output.
(2) In the magneto-impedance effect sensor according to the present invention, even if the output of the amplifier is about to be offset, the offset is automatically erased by the adjustment circuit. Therefore, even if the temperature condition or stray capacitance changes during running / scanning of the magneto-impedance effect sensor, it does not actually appear as an output change. It can be detected and measured accurately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a circuit diagram of an example of a magneto-impedance effect sensor used in the inspection method of an iron-based structure of the present invention.
In FIG. 1, reference numeral 1 denotes a magneto-impedance effect element, which has a zero magnetostriction or a negative magnetostriction having an outer shell portion in which magnetic domains whose spontaneous magnetization directions are opposite to each other in the circumferential direction of the wire are alternately separated by domain walls. Amorphous alloy wire is used. The inductance voltage component in the output voltage between both ends of the wire generated when a high-frequency excitation current is passed through an amorphous magnetic wire having zero magnetostriction or negative magnetostriction is obtained by the circumferential magnetic flux generated in the cross section of the wire. This occurs due to the magnetization of the easily magnetizable outer shell in the circumferential direction. Accordingly, the circumferential magnetic permeability μθ depends on the circumferential magnetization of the outer shell. Thus, when a signal magnetic field is applied in the axial direction of the amorphous wire being energized, the outer shell portion having the easily magnetizable property in the circumferential direction is obtained by synthesizing the circumferential magnetic flux and the signal magnetic field magnetic flux by the energization. The direction of the magnetic flux acting on the magnetic field is deviated from the circumferential direction, and magnetization in the circumferential direction is less likely to occur, the circumferential permeability μθ is changed, and the inductance voltage is changed. This fluctuation phenomenon is called a magnetic inductance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a signal magnetic field (signal wave). Further, when the frequency of the energizing current is in the order of MHz, a high-frequency skin effect appears greatly, and the skin depth δ = (2ρ / wμθ) ^1/2 (μθ is the circumferential permeability, as described above, and ρ is the electrical conductivity. (Resistivity, w indicates angular frequency) varies with μθ, and μθ varies with the signal magnetic field as described above, so the resistance voltage component in the output voltage across the wire also varies with the signal magnetic field. . This fluctuation phenomenon is called a magneto-impedance effect, which can be said to be a phenomenon in which the high-frequency excitation current (carrier wave) is modulated by a signal magnetic field (signal wave).

  In FIG. 1, 2 is a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element, and 3 is a signal magnetic field H (signal wave) acting in the axial direction of the magneto-impedance effect element. 4 is an amplifier circuit for amplifying the demodulated wave, 5 is an output terminal, 6 is a negative feedback coil, and 7 is a bias magnetic field coil.

In order to inspect an iron-based structure according to the present invention, the above-mentioned sensor is run along the iron-based structure while applying a bias magnetic field in which an alternating current is superimposed on a direct current component while applying an exciting current to the magneto-impedance effect element. Let me scan.
Magnet impedance effect element, negative feedback coil, bias magnetic field coil and substrate for mounting high frequency excitation current source, detection circuit, amplification circuit, and output terminal are separated into a magnetic impedance effect element and negative feedback coil. Further, only the bias magnetic field coil may be run or scanned.

2A, the straight line P indicates the output characteristics of the magneto-impedance effect element described in FIG. 7B, the magnetic field Hb indicates a bias magnetic field in which an AC magnetic field is superimposed on the DC magnetic field, and E indicates the bias magnetic field. The output when the external magnetic field Hex = 0 is shown.
When a sensor is running or scanning, if a defect such as a flaw, thinning, or rust exists in an iron-based structure such as an iron pipe, the reluctance of the magnetic circuit that passes through the defect changes, so that the magnetic impedance When the effect sensor passes, the bias magnetic field Hb changes and the output changes.
Therefore, the presence of a defect can be detected from the change in output.
The amplitude of the bias magnetic field is set so as to be within the linear range n or m in (b) of FIG.
The frequency of the AC component superimposed on the DC component of the bias magnetic field is set lower than the frequency of the excitation current.
If the frequency for alternating current is set low under these conditions, defects in the deep part can be detected well. When the defect exists only at a shallow position or when the iron-based structure is thin, it is advantageous in terms of detection sensitivity to increase the frequency of the alternating current as much as possible.

FIG. 2-2 shows the change of the bias magnetic field when the sensor passes over the defect of the iron-based structure. A change in the DC bias magnetic field is indicated by Δ, and a change in the AC bias magnetic field appears as a difference in peak values.
Normally, residual magnetism exists non-uniformly along the scanning route, and a DC magnetic field due to residual magnetism acts on the sensor as an external magnetic field.
Thus, if the DC component is cut from the detected output by a capacitor or the like, only the AC output change appears as indicated by E and E ′ in FIG. Therefore, it is possible to detect defects in the iron-based structure without being affected by the residual magnetism.
Further, it is possible to eliminate the inconvenience that the DC component of the detection output becomes large and the detector is shaken off.

Depending on the scanning route, the temperature condition may change greatly along the route, or the stray capacitance may change greatly and the offset value of the amplifier may change, which may hinder detection.
According to the magneto-impedance effect sensor according to claims 2 to 6, such inconvenience can be eliminated.

FIG. 3A shows a circuit diagram of an embodiment of the magneto-impedance effect sensor according to claim 2.
In FIG. 3A, 1 is a magneto-impedance effect element, 2 is a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element, and 3 is a signal magnetic field H (signal wave) acting in the axial direction of the magneto-impedance effect element. ) To demodulate the modulated wave obtained by modulating the high-frequency excitation current (carrier wave), 4 is an amplifier circuit for amplifying the demodulated wave, 5 is an output terminal, 6 is a negative feedback coil, and 7 is a bias magnetic field coil. It is.
Reference numeral 8 denotes an output correction circuit for generating an offset signal of an amplifier output as an input signal, generating a compensation signal for canceling the offset, and adding the compensation signal to the amplifier as an input for erasing the offset.

FIG. 3-2 shows an example of the output correction circuit. The offset is detected by comparing the output and input of the operational amplifier. When the offset is positive (negative), the electronic volume switches SW ₋₁ and SW ₋₂ are detected. ,... (SW _{+ 1} , SW _{+ 2} ,...) _Are sequentially turned on and off by the control IC, and a negative (positive) output voltage is sent to the offset adjustment terminal of the operational amplifier to reduce the offset of the amplifier output. When the offset becomes 0, the switch state at that time is held.
The offset of the output of the operational amplifier may be set within a predetermined range, for example, a range of −1v to + 1v. In this case, when the offset of the amplifier output exceeds 1v, the electronic volume is operated.
Further, a buffer having a gain of 1 or more, for example, 2 times, is incorporated in the control IC, and when the offset of the amplifier output exceeds ± 0.5 V, the electronic volume is operated so that the offset of the operational amplifier output is −0.5 V. It can also be set within the range of ~ 0.5V.

FIG. 4 shows a circuit diagram of an embodiment of a magneto-impedance effect sensor according to claim 3.
In FIG. 4, reference numerals 1a and 1b denote a pair of magneto-impedance effect elements each having negative feedback coils 6a and 6b and bias magnetic field coils 7a and 7b. Similar to the above, a bias magnetic field in which an alternating current is superimposed on a direct current is used, and the amplitude thereof is set to fall within the linear range n or m in (b) of FIG.
Reference numeral 2 denotes a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element. Reference numerals 3a and 3b denote signal magnetic fields Hex (signal waves) acting in the axial direction of the magneto-impedance effect elements 1a and 1b. A detection circuit 4 for demodulating the modulated wave having a modulated carrier wave) is an operational differential amplifier for obtaining a detection output by differentially amplifying both detection outputs. Reference numeral 60 denotes a negative feedback circuit for negatively feeding back the output of the differential amplifier 4 to the negative feedback coils 6a and 6b. Reference numeral 5 denotes a detection output terminal.
Reference numeral 8 denotes an output correction circuit which uses the offset of the operational differential amplifier 4 as an input signal, generates a compensation signal for canceling the offset, and adds this compensation signal to the amplifier as an input for erasing the offset. It is.
The output correction circuit shown in FIG. 3-2 can be used as described above, and the offset is detected by comparing the output and input of the operational differential amplifier. If the offset is positive (negative), the electronic volume Switches SW ₋₁ , SW ₋₂ ,... (SW ₊₁ , SW ₊₂ ,...) _Are sequentially turned on and off by the control IC, and a negative (positive) output signal is applied to the offset adjustment terminal of the operational differential amplifier. When the offset of the differential amplifier output is reduced and becomes zero, the switch state at that time is maintained.
The offset of the output of the operational differential amplifier may be set within a predetermined range, for example, a range of -1v to + 1v. In this case, when the offset of the differential amplifier output exceeds 1v, the electronic volume is manipulated.
In addition, a buffer with a gain of 1 or more, for example, 2 times, is incorporated in the control IC so that if the offset of the differential amplifier output exceeds ± 0.5 V, the electronic volume is operated to reduce the offset of the operational differential amplifier output. It can also be set within the range of -0.5v to + 0.5v.

FIG. 5A shows a circuit diagram of an embodiment of a magneto-impedance effect sensor according to claim 4.
5A, reference numerals 1a and 1b denote a pair of magneto-impedance effect elements, which respectively include negative feedback coils 6a and 6b and bias magnetic field coils 7a and 7b. Similar to the above, a bias magnetic field in which an alternating current is superimposed on a direct current is used, and the amplitude thereof is set to fall within the linear range n or m in (b) of FIG.
Reference numeral 2 denotes a high-frequency current source circuit for applying a high-frequency excitation current to the magneto-impedance effect element. Reference numerals 3a and 3b denote signal magnetic fields Hex (signal waves) acting in the axial direction of the magneto-impedance effect elements 1a and 1b. A detection circuit 4 for demodulating the modulated wave having a modulated carrier wave) is an operational differential amplifier for obtaining a detection output by differentially amplifying both detection outputs. Reference numeral 60 denotes a negative feedback circuit for negatively feeding back the output of the differential amplifier 4 to the negative feedback coils 6a and 6b. Reference numeral 5 denotes a detection output terminal.
Reference numeral 8 denotes an output correction circuit connected between both input terminals of the operational differential amplifier 4. The offset signal of the differential amplifier output is used as an input signal to generate a compensation signal for canceling the offset signal. Is added as an input for erasing the offset.

FIG. 5-2 (a) shows an example of the output correction circuit. The output of the differential amplifier is compared with the difference output of the differential amplifier to detect the offset of the differential amplifier, and the offset is shown in FIG. It is set to 0 by the volume operation shown in (b) of 5-2, and the electronic control switches SW ₀ , SW ₋₁ , SW ₋₂ ,..., SW ₀ , SW _+1,. This is done by operating SW ₊₂ .
Similarly to the above, the offset of the output of the operational differential amplifier may be set within a predetermined range, for example, the range of -1v to + 1v. In this case, the offset of the output of the operational differential amplifier is set to -1v or + 1v. If exceeded, the electronic volume is operated. In this case, the offset of the output of the operational differential amplifier is set to −0.5v to +0 so that the electronic volume is manipulated when a gain of 1 or more, for example, a double buffer is incorporated in the control IC and exceeds ± 0.5v. It is also possible to fit within the range of .5v.

  In the magneto-impedance effect element sensor according to the present invention, as the magneto-impedance effect element 1, an amorphous ribbon, an amorphous sputtered film, or the like can be used in addition to an amorphous wire having zero or negative magnetostriction.

In the magneto-impedance effect element sensor according to the present invention, the magneto-impedance effect element 1 includes an alloy of transition metal and non-metal having a non-metal composition of 10 to 30 atomic%, particularly an alloy of transition metal and non-metal. A composition in which the metal amount occupies 10 to 30 atomic% and the transition metal is Fe and Co and the nonmetal is B and Si or the transition metal is Fe and the nonmetal is B and Si can be used. For example, the composition Co _70.5 B ₁₅ Si ₁₀ Fe _4.5 , length 2000 μm to 6000 μm, and outer diameter 30 μm to 50 μmφ can be used.

  For the high-frequency excitation current, a normal high frequency such as a continuous sine wave, a pulse wave, or a triangular wave can be used. As the high-frequency excitation current source, for example, a Hartley oscillation circuit, a Colpitts oscillation circuit, a collector tuned oscillation circuit, a base tuned oscillation circuit In addition to the normal oscillation circuit, a square wave generator that integrates the square wave output of the crystal oscillator through a DC component cut-off capacitor with an integration circuit and amplifies the triangular wave of this integration output with an amplification circuit, and uses a CMOS-IC as the oscillation unit Can be used.

As the detection circuit, for example, a configuration in which a modulated wave is half-wave rectified by an operational amplifier circuit and the half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave, the modulated wave The half-wave rectified wave is processed by a diode, and the half-wave rectified wave is processed by a parallel RC circuit or an RC low-pass filter to obtain an envelope output of the half-wave rectified wave.
Further, it is possible to use tuning detection in which a signal wave is sampled by multiplying the modulated wave by a square wave having a frequency fs tuned to the modulated wave (frequency fs).
In the above embodiment, the signal magnetic field (signal wave) is extracted by demodulating the modulated wave. However, the present invention is not limited to this, and the high-frequency excitation current modulated by the signal magnetic field (signal wave) acting on the magneto-impedance effect element. As long as the signal magnetic field can be detected from the wave (carrier wave), an appropriate detection means can be used.

The negative feedback coil and the bias magnetic field coil can be wound around the magneto-impedance effect element. Further, as shown in FIG. 6, a negative feedback coil and a bias magnetic field coil can be wound around an iron core constituting a magneto-impedance effect element and a loop magnetic circuit.
6 (a) is a side view showing an example of a magneto-impedance effect unit with an iron core coil, FIG. 6 (b) is a bottom view, and FIG. 6 (c) is a diagram of FIG. 6 (b). It is sectional drawing.
In FIG. 6, reference numeral 100 denotes a substrate chip, for example, a ceramic plate can be used. Reference numeral 101 denotes an electrode provided on one side of the substrate piece, and includes a magneto-impedance effect element connecting projection 102. This electrode can be provided by printing and baking a conductive paste, for example, a silver paste. 1x is a magneto-impedance effect element connected between the protrusions 102 and 102 of the electrodes 101 and 101 by soldering or welding, and an amorphous wire, amorphous ribbon, sputtered film, or the like having zero or negative magnetostriction can be used as described above. 103 is a C-type iron core made of iron or ferrite, 6x is a negative feedback coil wound around the C-type iron core, 7x is a bias magnetic field coil, and the magneto-impedance effect element 1x and the C-type iron core 103 The both ends of the C-type iron core 103 are fixed to the other surface of the substrate piece 100 with an adhesive or the like so as to constitute a loop magnetic circuit. The iron core material may be a magnetic material having a small residual magnetic flux density. Examples thereof include permalloy, ferrite, iron, amorphous magnetic alloy, magnetic powder mixed plastic, and the like.

  In the magneto-impedance effect sensor according to the present invention, the negative feedback operation is effective for linearizing output characteristics and stabilizing the operation. This negative feedback can be omitted.

  The method for inspecting an iron-based structure according to the present invention includes, for example, corrosion of an inner surface of an iron-based pipe or an iron-based transport pipe used as a steel tower of a power transmission line, defects such as thinning, scratches, etc., embedded in concrete. It can be used to detect defects such as corrosion, thinning and flaws in steel pipes, detection of the buried position of the pipe, corrosion of steel bars in steel-reinforced concrete, thinning and defects such as flaws, detection of the position of the reinforcing bar. .

It is a circuit diagram which shows an example of the magnetic impedance effect sensor used for the inspection method of the iron-type structure which concerns on this invention. It is drawing which shows the bias magnetic field-sensor output characteristic in the inspection method of the iron system structure concerning the present invention. It is drawing which shows the bias magnetic field-sensor output characteristic at the time of the defect passage in the inspection method of the iron system structure concerning the present invention. It is a circuit diagram which shows one Example of the magneto-impedance effect sensor based on this invention. It is drawing which shows an example of the correction circuit of the magneto-impedance effect sensor of FIGS. It is a circuit diagram which shows the Example different from the above of the magneto-impedance effect sensor based on this invention. It is a circuit diagram which shows the Example different from the above of the magneto-impedance effect sensor based on this invention. It is drawing which shows an example of the correction circuit of the magneto-impedance effect sensor of FIGS. 1 is a diagram illustrating a magneto-impedance effect unit used in a magneto-impedance effect sensor according to the present invention. It is drawing which shows the output characteristic of a magneto-impedance effect element. 1 is a diagram illustrating a conventional magneto-impedance effect sensor. It is drawing which shows the input / output waveform in various places in the conventional magnetic impedance effect sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetoimpedance effect element 1a Magnetoimpedance effect element 1b Magnetoimpedance effect element 2 Excitation current source 3 Detection circuit 3a Detection circuit 3b Detection circuit 4 Amplifier or differential amplifier 5 Detection output terminal 6 Negative feedback magnetic field coil 6a Negative feedback magnetic field coil 6b Negative feedback magnetic field coil 7 Bias magnetic field coil 7a Bias magnetic field coil 7b Bias magnetic field coil 8 Correction circuit

Claims (6)

A magnetic field effect coil is attached to the magneto-impedance effect element, the output of the element is amplified by an amplifier, and a detection output is obtained. Travel along the iron-based structure while applying the superimposed bias magnetic field. During this travel, the bias magnetic field passes through the iron-based structure and the iron-based structure passes as part of the magnetic circuit, based on the defects in the iron-based structure. A method for inspecting an iron-based structure, wherein the detection output is changed by changing a bias magnetic field passing through a magneto-impedance effect element, and a defect in the iron-based structure is detected from the change. A bias magnetic field coil is attached to the magneto-impedance effect element, the output of the element is amplified by an amplifier to obtain a detection output, and an offset signal of the amplifier output is used as an input signal to generate a compensation signal to cancel the offset. A magneto-impedance effect sensor provided with a correction circuit for applying a compensation signal to the amplifier as an input for erasing the offset is supplied with a bias magnetic field in which an excitation current is applied to the magneto-impedance effect element and an AC component is superimposed on a DC component. While running, run along the iron-based structure, and during this travel, pass the bias magnetic field to the iron-based structure, pass the iron-based structure as part of the magnetic circuit, and install the magneto-impedance effect element based on the defects of the iron-based structure The detection output is changed by changing the bias magnetic field that passes through, and the defect of the iron-based structure is detected from this change. Inspection method of an iron-based structure, wherein. A bias magnetic field coil is attached to each of the pair of magneto-impedance effect elements, and the output of both elements is amplified by a differential amplifier to obtain a detection output, and the offset of the differential amplifier output is used as an input signal to cancel the offset. A magneto-impedance effect sensor provided with a correction circuit that generates a compensation signal and applies this compensation signal as an input for erasing the offset to the amplifier supplies an exciting current to the magneto-impedance effect element and alternating current into a DC component. Run along an iron-based structure while applying a bias magnetic field with superimposed components, and during this run, pass the bias magnetic field through the iron-based structure and pass the iron-based structure as part of the magnetic circuit. Based on this, the detection output is changed by changing the bias magnetic field passing through the magneto-impedance effect element. Inspection method of an iron-based structure, characterized in that to detect the defect. A bias magnetic field coil is attached to each of a pair of magneto-impedance effect elements, and the output of both elements is amplified by a differential amplifier to obtain a detection output, and the differential amplifier output offset between both input terminals of the differential amplifier A magneto-impedance effect sensor provided with a correction circuit for generating a compensation signal for canceling the offset as an input signal and providing the compensation signal as an input for erasing the offset to the amplifier While applying an exciting current and applying a bias magnetic field in which the AC component is superimposed on the DC component, the vehicle travels along the iron-based structure. During this traveling, the bias magnetic field is applied to the iron-based structure, and the iron-based structure is applied to the magnetic circuit. The detection output is changed by changing the bias magnetic field passing through the magneto-impedance effect element based on the defect of the iron-based structure. Is allowed, the inspection method of the iron-based structures and detecting defects in iron-based structure from this change. 5. The iron according to claim 2, wherein means for generating a compensation output when the offset of the amplifier or differential amplifier output reaches a predetermined value is added to the correction circuit of the magneto-impedance effect sensor. Inspection method for system structures. 6. The method of inspecting an iron-based structure according to claim 5, further comprising means for multiplying an offset of an amplifier or differential amplifier output of the magneto-impedance effect sensor by n (n> 1) and inputting the offset to a correction circuit.

Images