GB2109112A - Eddy current test probe - Google Patents
Eddy current test probe Download PDFInfo
- Publication number
- GB2109112A GB2109112A GB08130143A GB8130143A GB2109112A GB 2109112 A GB2109112 A GB 2109112A GB 08130143 A GB08130143 A GB 08130143A GB 8130143 A GB8130143 A GB 8130143A GB 2109112 A GB2109112 A GB 2109112A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coil
- sensing coils
- wound
- probe
- sensing
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000000523 sample Substances 0.000 title claims abstract description 18
- 238000012360 testing method Methods 0.000 title abstract description 5
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 8
- 230000005284 excitation Effects 0.000 claims description 15
- 239000000696 magnetic material Substances 0.000 claims description 7
- 239000000463 material Substances 0.000 description 6
- 239000004020 conductor Substances 0.000 description 2
- 239000002356 single layer Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
- G01N27/9006—Details, e.g. in the structure or functioning of sensors
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Abstract
The test probe has two mutually concentric sensing coils, 11, 13 connected in series and wound in opposite directions, the inner coil on a ferrite core 10 and the outer coil on the inner. The sensing coils each have nominally the same number of turns, but are 'balanced' in a calibrating magnetic field to constitute a differential configuration by the addition to or substraction from one coil of a turn or part of a turn. A field coil 14 is wound on the outer sensing coil. The probe has the advantage of being omnidirectional in effective operation in fault location using eddy current techniques. <IMAGE>
Description
SPECIFICATION
Eddy current test tube
This invention relates to apparatus for use in locating faults in electrically conductive bodies.
The invention is concerned particularly with such apparatus comprising means for producing a primary magnetic field or excitation field for probing the conductive body to induce eddy currents therein, and means for examining the resultant magnetic field.
In one previous proposal, such apparatus comprises a coil across which an alternating voltage is applied to produce the excitation field, and the same coil serves for examining the resultant field the examination being effected by interpreting changes in phase angles and amplitudes of voltages induced in the coil in relation to the applied voltage. This arrangement, called an 'absolute' configuration, has the disadvantage that there is always a high residual voltage present the removal of which tends to mask small amplitude and phase variations.
In another previous proposal, such apparatus comprises a separate field or excitation coil surrounding a side-by-side pair of sensing coils which are made mutually identical except for one being wound oppositely from the other. The sensing coils are connected in series so that they constitute a 'differential' configuration. In this case, examination of the resultant magnetic field is effected by interpreting the output voltages from the sensing coils in relation to zero volts or null reading.
However, this differential configuration has the disadvantage of possessing a directional characteristic which in certain modes of use prevents satisfactory location of some orientations of faults.
An object of the present invention is to provide apparatus for use in locating faults in conductive bodies, in which the above mentioned disadvantages are obviated or mitigated.
According to the present invention, there is provided apparatus for use in locating faults in conductive bodies comprising excitation means for producing an excitation magnetic field, and means for examining a resultant magnetic field produced when, in use, the excitation means is associated with a conductive body to be tested, said examining means comprising two mutually concentric sensing coils connected in series and wound one on the other in mutually opposed directions to constitute a differential configuration.
Preferably, the inner of the said two sensing coils is wound on a core of magnetic material.
Preferably, the magnetic material is ferrite.
Preferably, the excitation means comprises an excitation or field coil.
Preferably, the field coil is arranged concentric with the sensing coils.
Preferably, the field coil is wound on the outer sensing coil.
The excitation means and the means for examining a resultant magnetic field preferably comprise, respectively, an alternating voltage source connected to the field coil, and measuring means connected to the sensing coils and responsive to electrical voltage induced in the sensing coils.
The said measuring means may conveniently include an oscilloscope, and the visual interpretation of the trace based on experimental practice. Alternatively or additionally, the measuring means may include recording means, which may be analogue or digital, and the interpretation of the recorded data maybe assisted by means of a programmed data processor.
The field coil and the sensing coils together constitute an assembly known as a probe.
Further, according to the present invention, there is provided for use in the apparatus aforesaid, a probe comprising two mutually concentric sensing coils connected in series and wound one on the other in mutually opposed directions to constitute a differential configuration, and a field coil arranged concentric with the sensing coils.
Preferably, the probe includes a core of magnetic material, preferably ferrite.
In order to constitute a differential configuration, the voltages induced in the sensing coils by a 'calibrating' alternating magnetic field must respectively be mutually equal and of opposite polarity to produce a null reading.
In the previously proposed differential configuration, this is achieved, to an accuracy within acceptable tolerances, simply by winding the two sensing coils on similar cores and with the same number of turns. However, the sensing coils in accordance with the present invention, being wound one on or the other are of different diameter. Moreover, the mutually concentric sensing coils are much more closely coupled and therefore more mutually interactive than the coils of the prior arrangement. Accordingly, the mutually concentric sensing coils are 'balanced' by the addition or subtraction to or from one coil of a turn or part of a turn so that a null reading is obtained across both coils while they are in the calibrating field.
An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing which is a diagrammatic representation partly in sectional elevation of apparatus in accordance with the present invention.
In the drawing, a cylindrical ferrite core 10 has a single-layer first sensing coil 11 wound directly on to a lower portion of the core. At the lower termination of the first sensing coil
11, the electrical conductor, which is of enamelled copper wire, is folded as at 1 2 and a second single-layer sensing coil 1 3 is wound on the first sensing coil concentric therewith.
In the drawing, the sensing coils 11 and 1 3 are shown diagrammatically with the sensing coil 1 3 being represented by a heavier line for clarity. It will be understood however that both sensing coils are close-coiled and are of the same conductor material in respect of composition and wire gauge.
A field coil 14, shown diagrammatically in cross section, is arranged concentrically with the sensing coils. In practice, the field coil may be wound on the outer sensing coil.
The three coils and the ferrite core described above constitute a probe assembly and are, in practice, housed or encapsulated for example in a block of plastics material (not shown) with provision made for electrical leads and connections.
The apparatus includes an alternating voltage source 1 5 which is connected to the field coil 14, and also measuring means in the form of an oscilloscope 1 6 which is connected to the sensing coils.
The basic principles of eddy current testing are known and it will therfore be appreciated that the various electrical parameters and physical dimensions will be determined having regard to the nature of the material being tested and the depths in such material at which faults are to be located.
Typical physical dimensions for a probe to be used in examining for defects around fasteners in aircraft wing skins would be as follows. The ferrite core 1 0, 40mm in length and 1 2mm diameter; the sensing coils 11 and 1 3 each 80 turns (prior to balancing adjustment) of 43 gauge wire; and the field coil 14 having 600 turns of 36 gauge wire.
A probe thus dimensioned is useful in examining to a depth of the order of 1 Omm; or at operating frequencies down to 200 hertz.
In use, an altenating voltage applied to the field coil 14 produces an excitation field for probing an article to be tested as shown diagrammatically by reference numeral 1 7 in the drawing. The presence of the material of the article 1 7 alters the total impedance of the probe, and the degree of alteration of such impedance is affected by the presence of a fault in the material. Accordingly, the fault may be located by appropriate interpretation of the oscillscope trace.
Since the sensing coils 11 and 1 3 are mutually concentric, they are omni-directional in effective operation in fault location. The relatively high sensitivity of this probe permits test procedures including rapid linear scans in which serious faults are not missed as could be the case in using a probe having directional characteristics.
In the manufacture or construction of the probe, as has been explained hereinbefore, the sensing coils 11 and 1 3 are balanced by the addition or subtraction of a turn (or turns) or part of a turn to or from the upper end of one or the other coil while the prolbe is disposed in a calibrating field. The frequency of the calibrating field is chosen with reference to the designed operating frequencies for the tests for which the probe is intended.
Claims (11)
1. Apparatus for use in locating faults in conductive bodies comprising excitation means for producing an excitation magnetic field, and means for examining a resultant magnetic field produced when, in use, the excitation means is associated with a conductive body to be tested, said examining means comprising two mutually concentric sensing coils connected in series and wound one on the other in mutually opposed directions to constitute a differential configuration.
2. Apparatus according to claim 1, wherein the inner of the said two sensing coils is wound on a core of magnetic material.
3. Apparatus according to claim 2, wherein the magnetic material is ferrite.
4. Apparatus according to any one of the preceding claims, wherein the excitation means comprises an excitation or field coil.
5. Apparatus according to claim 4, wherein the field coil is arranged concentric with the sensing coils.
6. Apparatus according to claim 5, wherein the field coil is wound on the outer sensing coil.
7. A probe comprising two mutually concentric sensing coils connected in series and wound one on the other in mutually opposed directions to constitute a differential configuration, and a field coil arranged concentric with the sensing coils.
8. A probe according to claim 7, including a core of magnetic material.
9. A probe according to claim 8, wherein the magnetic material is ferrite.
10. Apparatus for use in locating faults in conductive bodies, substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
11. A probe substantially as hereinbefore described with reference to and as shown in the accompanying drawing.
1 2. Any feature or combination of features herein disclosed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08130143A GB2109112A (en) | 1981-10-06 | 1981-10-06 | Eddy current test probe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08130143A GB2109112A (en) | 1981-10-06 | 1981-10-06 | Eddy current test probe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2109112A true GB2109112A (en) | 1983-05-25 |
Family
ID=10524982
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08130143A Withdrawn GB2109112A (en) | 1981-10-06 | 1981-10-06 | Eddy current test probe |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2109112A (en) |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0543648A1 (en) * | 1991-11-21 | 1993-05-26 | Kaisei Engineer Co., Ltd. | Inspection device using electromagnetic induction and method therefor |
| FR2689638A1 (en) * | 1992-04-06 | 1993-10-08 | Aerospatiale | Eddy current sensor for defect detection - has U shaped magnetic support with cylindrical segment supporting excitation coil while magnetic rod with measuring coil engages bore in support |
| US5617024A (en) * | 1993-10-12 | 1997-04-01 | The United States Of America As Represented By The United States National Aeronautics And Space Administration | Flux focusing eddy current probe |
| US5648721A (en) * | 1993-10-12 | 1997-07-15 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Rotating flux-focusing eddy current probe for flaw detection |
| WO2002010737A3 (en) * | 2000-07-28 | 2003-02-27 | Gen Electric | Method and system for detecting stator core faults |
| EP1515137A1 (en) * | 2003-09-12 | 2005-03-16 | General Electric Company | Omni-directional eddy current probe |
| WO2006117530A3 (en) * | 2005-04-29 | 2007-02-01 | Univ London | Apparatus and method for determining magnetic properties of materials |
| US8212554B2 (en) | 2005-05-11 | 2012-07-03 | The University Of Houston System | Intraluminal magneto sensor system and method of use |
| US8380279B2 (en) | 2005-05-11 | 2013-02-19 | The University Of Houston System | Intraluminal multifunctional sensor system and method of use |
| US9234877B2 (en) | 2013-03-13 | 2016-01-12 | Endomagnetics Ltd. | Magnetic detector |
| US9239314B2 (en) | 2013-03-13 | 2016-01-19 | Endomagnetics Ltd. | Magnetic detector |
| US9427186B2 (en) | 2009-12-04 | 2016-08-30 | Endomagnetics Ltd. | Magnetic probe apparatus |
| US9658192B2 (en) | 2012-01-23 | 2017-05-23 | Siemens Corporation | Insulation defect detection of high voltage generator stator core |
| US9808539B2 (en) | 2013-03-11 | 2017-11-07 | Endomagnetics Ltd. | Hypoosmotic solutions for lymph node detection |
| CN108562641A (en) * | 2018-04-17 | 2018-09-21 | 西南大学 | A kind of cable core material quality detecting device based on current vortex sensor |
| US10595957B2 (en) | 2015-06-04 | 2020-03-24 | Endomagnetics Ltd | Marker materials and forms for magnetic marker localization (MML) |
| US10634741B2 (en) | 2009-12-04 | 2020-04-28 | Endomagnetics Ltd. | Magnetic probe apparatus |
-
1981
- 1981-10-06 GB GB08130143A patent/GB2109112A/en not_active Withdrawn
Cited By (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0543648A1 (en) * | 1991-11-21 | 1993-05-26 | Kaisei Engineer Co., Ltd. | Inspection device using electromagnetic induction and method therefor |
| US5548214A (en) * | 1991-11-21 | 1996-08-20 | Kaisei Engineer Co., Ltd. | Electromagnetic induction inspection apparatus and method employing frequency sweep of excitation current |
| FR2689638A1 (en) * | 1992-04-06 | 1993-10-08 | Aerospatiale | Eddy current sensor for defect detection - has U shaped magnetic support with cylindrical segment supporting excitation coil while magnetic rod with measuring coil engages bore in support |
| US5617024A (en) * | 1993-10-12 | 1997-04-01 | The United States Of America As Represented By The United States National Aeronautics And Space Administration | Flux focusing eddy current probe |
| US5648721A (en) * | 1993-10-12 | 1997-07-15 | The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration | Rotating flux-focusing eddy current probe for flaw detection |
| WO2002010737A3 (en) * | 2000-07-28 | 2003-02-27 | Gen Electric | Method and system for detecting stator core faults |
| EP1515137A1 (en) * | 2003-09-12 | 2005-03-16 | General Electric Company | Omni-directional eddy current probe |
| US6888347B2 (en) | 2003-09-12 | 2005-05-03 | General Electric Company | Omnidirectional eddy current probes, array probes, and inspection systems |
| WO2006117530A3 (en) * | 2005-04-29 | 2007-02-01 | Univ London | Apparatus and method for determining magnetic properties of materials |
| EP2267471A1 (en) * | 2005-04-29 | 2010-12-29 | University College London | Probe for detecting magnetic properties of materials |
| US8174259B2 (en) | 2005-04-29 | 2012-05-08 | University Of Houston | Apparatus and method for determining magnetic properties of materials |
| US8380279B2 (en) | 2005-05-11 | 2013-02-19 | The University Of Houston System | Intraluminal multifunctional sensor system and method of use |
| US8212554B2 (en) | 2005-05-11 | 2012-07-03 | The University Of Houston System | Intraluminal magneto sensor system and method of use |
| US10634741B2 (en) | 2009-12-04 | 2020-04-28 | Endomagnetics Ltd. | Magnetic probe apparatus |
| US9427186B2 (en) | 2009-12-04 | 2016-08-30 | Endomagnetics Ltd. | Magnetic probe apparatus |
| US11592501B2 (en) | 2009-12-04 | 2023-02-28 | Endomagnetics Ltd. | Magnetic probe apparatus |
| US12092708B2 (en) | 2009-12-04 | 2024-09-17 | Endomagnetics Ltd. | Magnetic probe apparatus |
| US9658192B2 (en) | 2012-01-23 | 2017-05-23 | Siemens Corporation | Insulation defect detection of high voltage generator stator core |
| US9808539B2 (en) | 2013-03-11 | 2017-11-07 | Endomagnetics Ltd. | Hypoosmotic solutions for lymph node detection |
| US9239314B2 (en) | 2013-03-13 | 2016-01-19 | Endomagnetics Ltd. | Magnetic detector |
| US9523748B2 (en) | 2013-03-13 | 2016-12-20 | Endomagnetics Ltd | Magnetic detector |
| US9234877B2 (en) | 2013-03-13 | 2016-01-12 | Endomagnetics Ltd. | Magnetic detector |
| US10595957B2 (en) | 2015-06-04 | 2020-03-24 | Endomagnetics Ltd | Marker materials and forms for magnetic marker localization (MML) |
| US11504207B2 (en) | 2015-06-04 | 2022-11-22 | Endomagnetics Ltd | Marker materials and forms for magnetic marker localization (MML) |
| US12161513B2 (en) | 2015-06-04 | 2024-12-10 | Endomagnetics Ltd | Marker materials and forms for magnetic marker localization (MML) |
| CN108562641A (en) * | 2018-04-17 | 2018-09-21 | 西南大学 | A kind of cable core material quality detecting device based on current vortex sensor |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |