[go: up one dir, main page]

WO2015058733A1 - Contactless magnetic sensor of the magnetic or electrically conductive objects´position - Google Patents

Contactless magnetic sensor of the magnetic or electrically conductive objects´position Download PDF

Info

Publication number
WO2015058733A1
WO2015058733A1 PCT/CZ2014/000117 CZ2014000117W WO2015058733A1 WO 2015058733 A1 WO2015058733 A1 WO 2015058733A1 CZ 2014000117 W CZ2014000117 W CZ 2014000117W WO 2015058733 A1 WO2015058733 A1 WO 2015058733A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor
magnetic field
excitation
signal
excitation coil
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.)
Ceased
Application number
PCT/CZ2014/000117
Other languages
French (fr)
Inventor
Pavel Ripka
Jan VYHNÁNEK
Jan VČELÁK
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Czech Technical University In Prague
Original Assignee
Czech Technical University In Prague
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Czech Technical University In Prague filed Critical Czech Technical University In Prague
Publication of WO2015058733A1 publication Critical patent/WO2015058733A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/945—Proximity switches
    • H03K17/95—Proximity switches using a magnetic detector
    • H03K17/9517—Proximity switches using a magnetic detector using galvanomagnetic devices
    • 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
    • G01N27/9046—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 by analysing electrical signals
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/06—Measuring direction or magnitude of magnetic fields or magnetic flux using galvano-magnetic devices
    • G01R33/09—Magnetoresistive devices
    • G01R33/096—Magnetoresistive devices anisotropic magnetoresistance sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/10—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices using induction coils

Definitions

  • the subject of this invention is a contactless sensor of the magnetic or electrically conductive objects' position capable of detecting objects even behind metallic sheath.
  • the sensor uses a method of the signal self-demodulation.
  • Standard induction-type proximity/position sensors are based on generation of eddy currents in the approaching electrically conductive object, see e.g. patents US2013229174, US6803757 and US4042876.
  • Another large group of position/proximity sensors are sensors with variable magnetic circuit (see e.g. US5027066) or with saturable coil core - see e.g. US 4719362, US4587486, US4140971, EP 0538037 B1.
  • Last type is a magnetic position sensor using the permanent magnet direct current magnetic field detection - see e.g. JP3460363 and US484116.
  • Fig. 1 Sensors operating on the induction principle, Fig. 1 , consist of the excitation coil 10 excited by the source 20 of alternating current.
  • the sensor detects the position of conductive or ferromagnetic object 50.
  • the coil inductance changes as either a conductive object or permanent magnet approaches.
  • Output amplifier 60 with the signal processing circuit 61 usually evaluates losses in the coil, that are converted to binary or continuous information about the object's position.
  • eddy currents are induced in the object and their magnetic field acts against the field that induced them. This leads to reduced inductance of the excitation coil 10, higher losses and overall decrease of the excitation coil quality factor.
  • Proximity sensors very often Use coils excited in resonance, and the RLC circuit resonance vanish when the conductive object approaches, or the RLC circuit frequency changes as the conductive material approaches or recedes (Tumanski S, Thin film magnetoresistive sensors, ISBN-10: 0750307021 , 1SBN-13: 978- 0750307024, Edition: 1st, IOP (2001) and Ripka P. Magnetic Sensors and Magnetometers, ISBN-10: 1580530575, ISBN-13: 978-1580530576, Artech House Publishing (2001)). Induction sensors operate at excitation frequencies 1-100 kHz. The advantage of this solution is simple and inexpensive design.
  • the induction methods drawback is the dependence of the induced voltage on frequency; the higher the frequency, the higher the induced voltage and sensitivity of the sensor. In general, this is the reason why these sensors cannot be used at frequencies lower than 1 kHz. On the other hand, as the frequency gets higher, the penetration depth decreases, and the sensor is affected by stray capacitances.
  • the magnetic field induced by the eddy currents may be measured by other magnetic field sensor.
  • the example may be the AMR/GMR sensor located in the excitation coil that measures the overall magnetic field, Fig. 2.
  • Fig. 2 shows the block diagram of the proximity/position sensor using the inductance coil 10 excited by the source 20 of the alternating current.
  • the sensor detects the position of a conductive or ferromagnetic object 50.
  • the resulting field formed by the combination of the coil excitation and near conductive object 50 or a permanent magnet is detected by the magnetic field sensor 40.
  • Signal from the sensor is amplified by the amplifier 60 and evaluated by synchronous demodulator 61..
  • the demodulator output is the measure-bearing quality.
  • the overall measured field decreases due to the effects of eddy currents in the detected conductive object 50.
  • the contact!ess magnetic sensor of the magnetic or electrically conductive objects' position consisting of at least one excitation coil connected to a source of the alternating signal where the magnetic field sensor is located in the cavity of the excitation coil.
  • the output of the magnetic field sensor is connected to the input of an amplifier, the output of which is connected to the input of the low-pass filter, to the input of the band-pass filter and to the input of the high-pass filter.
  • the connection further includes an excitation modulator.
  • the principle of the new solution is that the modulator of the sensor's magnetic field excitation is connected to a source of the alternating excitation signal for the coil.
  • the source of the alternating excitation signal is a source of rectangular-shaped signal.
  • Magnetic field sensor may also be formed by a Hall probe or by an anisotropic magnetoresistor.
  • the magnetic field sensor excitation modulator is formed by a separating capacitor. One terminal of the separating capacitor is connected to the flipping input of the anisotropic magnetoresistor and the other terminal is connected to the source of the alternating excitation voltage for the excitation coil.
  • the advantage of proposed sensor is its sensitivity to direct current magnetic field as well as to alternating current field induced by eddy currents in conductive materials.
  • the sensor is capable to detect wide range of materials and to discriminate, which material is being detected at a given moment.
  • Materials that can be detected may be electrically conductive non-magnetic materials, such as Al, Cu; soft magnetic materials, hard magnetic materials, i.e. permanent magnets; or combination of the materials mentioned above.
  • the proposed sensor significantly simplifies the electronic circuitry needed for the sensor's signal evaluation. It exploits the principle of self-demodulation when the magnetic field sensor's output is modulated by identical or derived signal as the excitation coil.
  • Fig. 1 and Fig. 2 schematically show the presently known sensors of position or proximity of metallic or electrically conductive objects.
  • Fig. 3 shows the block diagram of the position/proximity sensor exploiting self-demodulation principle according to the presented solution.
  • the coil 10 is excited by the signal from the source 20 of excitation signal 20.
  • Flipping circuit of the magnetic field sensor 40 anisotropic magnetoresistor
  • the sensor output signal is amplified by the amplifier 60 and processed by filters of various types 80, 81, 82.
  • the sensor allows to detect proximity-position of conductive or ferromagnetic object 50 through a sheath made of conductive material 70.
  • Fig. 4.1 shows the excitation coil voltage waveform.
  • Fig. 4.2 shows the flipping current waveform of the anisotropic magnetoresistor, which here forms the magnetic field sensor.
  • Fig. 4.3 shows the output voltage waveform of the relevant sensor when it is placed in zero magnetic field and when in the vicinity of such sensor no conductive object or permanent magnet is present. Direct current value of the waveform is given by the magnetic field intensity generated directly by the excitation coil.
  • Fig. 4.4 shows the output voltage waveform of the sensor in case when the sensor measures external magnetic field of non-zero value - for example when a permanent magnet is present close to the sensor.
  • Fig. 4.5 shows the output voltage waveform of the sensor in case when a conductive object is present close to the sensor.
  • Fig. 4.6 shows the output voltage waveform of the sensor in case when the sensor measures proximity/position of the object, permanent magnet in this case, through a conductive (Al) sheath 70.
  • Fig. 5.2 to 5.4 show the output voltage waveforms after processing the sensor output voltage LUt by filters, which are the low-pass filter Ui, band-pass filter lb and high-pass filter lb.
  • filters which are the low-pass filter Ui, band-pass filter lb and high-pass filter lb.
  • the principle of presented invention is a position/proximity sensor exploiting an improved method of material detection.
  • the sensor shown schematically in Fig. 3, consists of the source 20 of the alternating, advantageously rectangular- shaped excitation signal, the excitation coil 10 or a setup of coils, excitation modulator 2J . , magnetic field sensor 40 located in the excitation coil 10 cavity, while its output is connected to input of the amplifier 60.
  • Excitation modulator 21 exciting the magnetic field sensor 40 is connected to the source 20 of the alternating excitation signal.
  • the output of amplifier 60 is connected to the input of the low-pass filter 80, to the input of the band-pass filter 81 , and to the input of the high-pass filter 82.
  • the following is an example when the sensor allows to detect proximity-position of a conductive or ferromagnetic object 50 through a sheath made of conductive material 70.
  • the source 20 of the alternating signal for the excitation coil 10 generates current with rectangular waveform with given frequency f and amplitude /.
  • the source 20 of the alternating signal is connected to contacts of the excitation coil 10.
  • Current / passing through the excitation coil 10 generates alternating current magnetic field that induces eddy currents in the detected conductive material which is present nearby.
  • Magnetic field sensor 40 is located in the center of the excitation coil 10 in such a way that it sensitivity axis is identical with the axis of the excitation coil 10, it means with the normal line of the excitation coil 10 passing through its imaginary center.
  • the magnetic field sensor 40 may be formed by an anisotropic magnetoresistor (AMR) or a Hall probe.
  • AMR anisotropic magnetoresistor
  • the AMR sensor as such consists of the dedicated AMR element that measures the magnetic field, a flipping coil and possibly a compensating coil. Signal that excites the coil is via the separating capacitor 30 connected directly to the flipping input of the coil of the AMR sensor. If an ambient DC magnetic field is present, it would lead to modulation of the sensor's output. Since the excitation signal of the excitation coil 10. and therefore the generated magnetic field are in-phase, and the magnetic field sensor 40 is modulated, it results in controlled rectification of the sensor's output signal and self-demodulation of the output signal.
  • the capacitor 30 ensures the AMR element flipping by means of narrow current pulses. This provides self- demodulation of the magnetic field sensor's 40 output without the need for additional electronics or synchronous demodulator.
  • the magnetic field sensor 40 is amplified by the amplifier 60 with the voltage Uout at its output 90, which is processed by three basic filters, specifically by the low-pass filter 80, the band-pass filter 81, and the high-pass filter 82.
  • the sensor's output signal may feature waveforms shown in Fig. 4.1 to 4.6 and 5.1 to 5.4.
  • UA is the voltage in the first half-period of the excitation signal and UB is the voltage in the second half-period of the excitation signal.
  • This voltage consists of several components.
  • Component UAC is proportional to the intensity of the magnetic field generated by the excitation coil 10 itself, possibly amplified, when a soft-magnetic material is present nearby.
  • Component UDC is proportional to the external direct current magnetic field generated for instance by permanent magnet or the Earth's magnetic field.
  • Components shown by bold lines represent the effects of eddy currents generated as a response to excitation field in the objects 50 made of electrically conductive materials.
  • the result is the voltage y_i, which corresponds to the mean value of the Uout signal.
  • Ui is equal to the value of UAC, which is directly proportional to the intensity of the magnetic field generated by the excitation coil 10, possibly amplified by the soft-magnetic material in its vicinity.
  • the signal is filtered by the band-pass filter 81 set at the frequency equal to the excitation signal frequency f, the result is the signal L while according to the equation (4) its total amplitude, it means its peak-to-peak value, is equal to 2 UDC and therefore it is directly proportional to the measured external direct current magnetic field.
  • the resulting signal U_3 corresponds only to the effects of eddy currents and therefore the proximity of object 50 made of conductive material.
  • the sensor When detecting the alternating current magnetic field, the sensor is functional already from very low frequencies where the induction-based sensors feature low sensitivity.
  • the AMR sensor's sensitivity is frequency independent up to the frequencies below 100 kHz.
  • the magnetic field penetration depth depends on the excitation field frequency. The higher the frequency, the lower the penetration depth.
  • Using the AMR sensors as the magnetic field detector allows to use low excitation frequencies and thus increase the penetration depth.
  • such sensor may be used for measuring the position of objects behind the sheath made of electrically conductive material.
  • the proposed sensor significantly simplifies the electronic circuitry needed to evaluate the signal from the sensor. It uses the principle of self-demodulation when the magnetic field sensor's output is modulated by the identical or derived signal as the excitation coil.
  • Filtering the sensor output signal allows to discriminate the detected materials based on their electric and magnetic properties. This brings extra benefit in situations when the detected material is not known in advance.
  • this sensor works also as the position sensor detecting objects behind electrically conductive sheath. It is possible to measure position of an object made of ferromagnetic material behind an sheath made of conductive non-ferromagnetic material, such as aluminium or copper. In case the object 50, position of which is to be detected, is hidden behind a metal sheet made of magnetic material, its position may be measured when the magnetic material of the cover 70 is magnetically saturated.
  • the sensor measures both the direct current component of the magnetic field as well as the response of the eddy currents. Evaluation of the output signal allows to obtain the information not only about the position but also about the type of the material in proximity. The sensor's output response allows also to discriminate the detected materials as conductive, ferromagnetic or their combinations.
  • a device shown in Fig. 3 was produced. It consists of the circular-shaped excitation coil 10 with 75 turns with the diameter of 46 mm and length of 22 mm.
  • the excitation coil 10 is powered by the source 20 of the alternating signal by rectangular-shaped current with the amplitude of 70 mA p-p and frequency 1 kHz. Applied frequency may vary, depending on the required penetration depth.
  • the excitation coil 10 generates around the magnetic field sensor 40, which in this case is an AMR sensor, an alternating current magnetic field with the intensity of 115 A/m.
  • the magnetic field sensor 40 flipping is provided by the integrated coil in the magnetic field sensor 40 with pulse current 1.2 A p-p by the discharge of capacitor 30 with the capacity of 6.8 nF.
  • Excitation modulator 30 is formed by the capacitor, which is directly connected to the excitation signal from the source 20 of the alternating signal 30 V p-p. in the center of the excitation coil 10 is located magnetic field sensor 40 l- MC1001. The output of the magnetic field sensor 40 is amplified by the amplifier 60 and subject for subsequent signal processing by individual filters.
  • Sensor featuring self-demodulation may be used for detection of position/proximity of an object behind the sheath made of electrically conductive materials, such as aluminium sheet, zinc-galvanized metal sheet, etc.
  • the sensor may be used as a position switch located behind a metal sheath or as the position switch with the closing phase detection.
  • the sensor may be used as a detector of metal parts befiind the cover made of conductive materials.
  • Described sensor may be used for non-destructive contactless flaw detection of thickness/condition of storage tanks or piping through metal cover and insulation layer. Comparative measurements allow to determine the degree of corrosion or disruption of the inner wall.
  • Described sensor may be used for discrimination of materials to electrically conductive ones, soft-magnetic ones and hard-magnetic ones or their combinations. In addition, it is possible to measure the magnitude of each component and thus to estimate the proximity of an object, its position or size.

Landscapes

  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Remote Sensing (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Geophysics (AREA)
  • Chemical & Material Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Electromagnetism (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

The contactless magnetic sensor consists of at least one excitation coil (10) connected to the source (20) of alternating signal. In thejcavity of the excitation coil (10) is located a magnetic field sensor (40) and its output is connected to the input of the amplifier (60). The sensor includes an excitation modulator (21), which is connected to the source (20). Output of the amplifier (60) is connected to the input of a low-pass filter (80), to the input of a band-pass filter (81), and to the input of a high-pass filter (82). The source (20) generates alternating, advantageously rectangular-shaped current, which generates an alternating current magnetic field around the excitation coil (10) that interacts with materials in the excitation coil (10) vicinity. The magnetic field sensor (40) may be an anisotropic magnetoresistor AMR or a Hall probe. In case of an AMR sensor the excitation signal of the excitation coil (10) is connected via the separating capacitor (30) directly to the flipping input of the AMR sensor coil. Since the excitation signal of the excitation coil (10), and therefore the generated magnetic field are in-phase, and the magnetic field sensor's output is modulated by the flipping circuit, the result is a controlled rectification of the sensor's output signal and self-demodulation of the output signal. The output of the sensor may therefore be used for position detection, proximity detection or discrimination of materials in the coil vicinity.

Description

Contactless magnetic sensor of the magnetic or electrically conductive objects' position
Background of the Invention
The subject of this invention is a contactless sensor of the magnetic or electrically conductive objects' position capable of detecting objects even behind metallic sheath. The sensor uses a method of the signal self-demodulation.
Description of Prior Art
Contactless position/proximity sensors have been known and widely used for many years already. Most commonly they use optical methods, capacity methods, ultrasound or magnetic/induction methods or their combinations. Proximity or position sensors are used in almost all industrial branches. Contactless measurement of position is used with advantage at automatic production lines in industrial automation as well as in automotive and aviation industries.
Standard induction-type proximity/position sensors are based on generation of eddy currents in the approaching electrically conductive object, see e.g. patents US2013229174, US6803757 and US4042876. Another large group of position/proximity sensors are sensors with variable magnetic circuit (see e.g. US5027066) or with saturable coil core - see e.g. US 4719362, US4587486, US4140971, EP 0538037 B1. Last type is a magnetic position sensor using the permanent magnet direct current magnetic field detection - see e.g. JP3460363 and US484116.
Sensors operating on the induction principle, Fig. 1 , consist of the excitation coil 10 excited by the source 20 of alternating current. The sensor detects the position of conductive or ferromagnetic object 50. Depending on the distance, the coil inductance changes as either a conductive object or permanent magnet approaches. Output amplifier 60 with the signal processing circuit 61 usually evaluates losses in the coil, that are converted to binary or continuous information about the object's position. When the detected object 50 made of conductive material approaches, eddy currents are induced in the object and their magnetic field acts against the field that induced them. This leads to reduced inductance of the excitation coil 10, higher losses and overall decrease of the excitation coil quality factor. These changes are amplified by the amplifier 60 and subsequently detected in the evaluation circuit 61 and converted to the measured quality. Proximity sensors very often Use coils excited in resonance, and the RLC circuit resonance vanish when the conductive object approaches, or the RLC circuit frequency changes as the conductive material approaches or recedes (Tumanski S, Thin film magnetoresistive sensors, ISBN-10: 0750307021 , 1SBN-13: 978- 0750307024, Edition: 1st, IOP (2001) and Ripka P. Magnetic Sensors and Magnetometers, ISBN-10: 1580530575, ISBN-13: 978-1580530576, Artech House Publishing (2001)). Induction sensors operate at excitation frequencies 1-100 kHz. The advantage of this solution is simple and inexpensive design. The induction methods drawback is the dependence of the induced voltage on frequency; the higher the frequency, the higher the induced voltage and sensitivity of the sensor. In general, this is the reason why these sensors cannot be used at frequencies lower than 1 kHz. On the other hand, as the frequency gets higher, the penetration depth decreases, and the sensor is affected by stray capacitances.
Instead of the inductance coil itself, the magnetic field induced by the eddy currents may be measured by other magnetic field sensor. The example may be the AMR/GMR sensor located in the excitation coil that measures the overall magnetic field, Fig. 2. Fig. 2 shows the block diagram of the proximity/position sensor using the inductance coil 10 excited by the source 20 of the alternating current. The sensor detects the position of a conductive or ferromagnetic object 50. The resulting field formed by the combination of the coil excitation and near conductive object 50 or a permanent magnet is detected by the magnetic field sensor 40. Signal from the sensor is amplified by the amplifier 60 and evaluated by synchronous demodulator 61.. The demodulator output is the measure-bearing quality. When the conductive object 50 is present, the overall measured field decreases due to the effects of eddy currents in the detected conductive object 50.
This method is widely used in flaw detection and for a non-destructive testing of materials for inhomogeneities and integrity defects US20120274319, US20020130659, US6888346, US6504363, EP0228473. The last three mentioned documents use the low-pass filter for noise filtering or extraction of the signal mean value, or the band-pass filter for interference filtering prior subsequent signal evaluation. The main drawback of this solution is its complex design that requires both - the suitable flipping circuit of the AMR sensor, and the synchronous demodulation of the signal from the sensor. Another drawback of the solutions mentioned above is that the sensors are capable of detecting only the given type of material, for which they are designed. They cannot discriminate detected materials or combination of various materials.
Summary of the Invention
Disadvantages mentioned above are removed by the contact!ess magnetic sensor of the magnetic or electrically conductive objects' position consisting of at least one excitation coil connected to a source of the alternating signal where the magnetic field sensor is located in the cavity of the excitation coil. The output of the magnetic field sensor is connected to the input of an amplifier, the output of which is connected to the input of the low-pass filter, to the input of the band-pass filter and to the input of the high-pass filter. The connection further includes an excitation modulator. The principle of the new solution is that the modulator of the sensor's magnetic field excitation is connected to a source of the alternating excitation signal for the coil. Advantageously, the source of the alternating excitation signal is a source of rectangular-shaped signal.
Magnetic field sensor may also be formed by a Hall probe or by an anisotropic magnetoresistor. When the anisotropic magnetoresistor is used, the magnetic field sensor excitation modulator is formed by a separating capacitor. One terminal of the separating capacitor is connected to the flipping input of the anisotropic magnetoresistor and the other terminal is connected to the source of the alternating excitation voltage for the excitation coil.
The advantage of proposed sensor is its sensitivity to direct current magnetic field as well as to alternating current field induced by eddy currents in conductive materials. The sensor is capable to detect wide range of materials and to discriminate, which material is being detected at a given moment. Materials that can be detected may be electrically conductive non-magnetic materials, such as Al, Cu; soft magnetic materials, hard magnetic materials, i.e. permanent magnets; or combination of the materials mentioned above.
In contrary to the standard solution, the proposed sensor significantly simplifies the electronic circuitry needed for the sensor's signal evaluation. It exploits the principle of self-demodulation when the magnetic field sensor's output is modulated by identical or derived signal as the excitation coil.
Explanation of Drawings
Fig. 1 and Fig. 2 schematically show the presently known sensors of position or proximity of metallic or electrically conductive objects.
Fig. 3 shows the block diagram of the position/proximity sensor exploiting self-demodulation principle according to the presented solution. The coil 10 is excited by the signal from the source 20 of excitation signal 20. Flipping circuit of the magnetic field sensor 40 (anisotropic magnetoresistor) is via the separating capacitor 30 connected to the same source 20 of the excitation signal. The sensor output signal is amplified by the amplifier 60 and processed by filters of various types 80, 81, 82. The sensor allows to detect proximity-position of conductive or ferromagnetic object 50 through a sheath made of conductive material 70.
Fig. 4.1 shows the excitation coil voltage waveform.
Fig. 4.2 shows the flipping current waveform of the anisotropic magnetoresistor, which here forms the magnetic field sensor.
Fig. 4.3 shows the output voltage waveform of the relevant sensor when it is placed in zero magnetic field and when in the vicinity of such sensor no conductive object or permanent magnet is present. Direct current value of the waveform is given by the magnetic field intensity generated directly by the excitation coil.
Fig. 4.4 shows the output voltage waveform of the sensor in case when the sensor measures external magnetic field of non-zero value - for example when a permanent magnet is present close to the sensor.
Fig. 4.5 shows the output voltage waveform of the sensor in case when a conductive object is present close to the sensor.
Fig. 4.6 shows the output voltage waveform of the sensor in case when the sensor measures proximity/position of the object, permanent magnet in this case, through a conductive (Al) sheath 70.
Fig. 5.2 to 5.4 show the output voltage waveforms after processing the sensor output voltage LUt by filters, which are the low-pass filter Ui, band-pass filter lb and high-pass filter lb. Detailed Description of the Preferred Embodiments
The principle of presented invention is a position/proximity sensor exploiting an improved method of material detection. The sensor, shown schematically in Fig. 3, consists of the source 20 of the alternating, advantageously rectangular- shaped excitation signal, the excitation coil 10 or a setup of coils, excitation modulator 2J., magnetic field sensor 40 located in the excitation coil 10 cavity, while its output is connected to input of the amplifier 60. Excitation modulator 21 exciting the magnetic field sensor 40 is connected to the source 20 of the alternating excitation signal. The output of amplifier 60 is connected to the input of the low-pass filter 80, to the input of the band-pass filter 81 , and to the input of the high-pass filter 82. The following is an example when the sensor allows to detect proximity-position of a conductive or ferromagnetic object 50 through a sheath made of conductive material 70.
The source 20 of the alternating signal for the excitation coil 10 generates current with rectangular waveform with given frequency f and amplitude /. The source 20 of the alternating signal is connected to contacts of the excitation coil 10. Current / passing through the excitation coil 10 generates alternating current magnetic field that induces eddy currents in the detected conductive material which is present nearby. Magnetic field sensor 40 is located in the center of the excitation coil 10 in such a way that it sensitivity axis is identical with the axis of the excitation coil 10, it means with the normal line of the excitation coil 10 passing through its imaginary center. The magnetic field sensor 40 may be formed by an anisotropic magnetoresistor (AMR) or a Hall probe. The AMR sensor as such consists of the dedicated AMR element that measures the magnetic field, a flipping coil and possibly a compensating coil. Signal that excites the coil is via the separating capacitor 30 connected directly to the flipping input of the coil of the AMR sensor. If an ambient DC magnetic field is present, it would lead to modulation of the sensor's output. Since the excitation signal of the excitation coil 10. and therefore the generated magnetic field are in-phase, and the magnetic field sensor 40 is modulated, it results in controlled rectification of the sensor's output signal and self-demodulation of the output signal. The capacitor 30 ensures the AMR element flipping by means of narrow current pulses. This provides self- demodulation of the magnetic field sensor's 40 output without the need for additional electronics or synchronous demodulator. Combined effects of the excitation coil's 10 field, the field generated by eddy currents in nearby conductive material and the external magnetic field are detected by the magnetoresistor or other magnetic field sensor. The magnetic field sensor 40 is amplified by the amplifier 60 with the voltage Uout at its output 90, which is processed by three basic filters, specifically by the low-pass filter 80, the band-pass filter 81, and the high-pass filter 82.
The sensor's output signal may feature waveforms shown in Fig. 4.1 to 4.6 and 5.1 to 5.4. UA is the voltage in the first half-period of the excitation signal and UB is the voltage in the second half-period of the excitation signal. This voltage consists of several components. Component UAC is proportional to the intensity of the magnetic field generated by the excitation coil 10 itself, possibly amplified, when a soft-magnetic material is present nearby. Component UDC is proportional to the external direct current magnetic field generated for instance by permanent magnet or the Earth's magnetic field.
Components shown by bold lines represent the effects of eddy currents generated as a response to excitation field in the objects 50 made of electrically conductive materials.
When the signal is filtered by the low-pass filter 80, the result is the voltage y_i, which corresponds to the mean value of the Uout signal. According to the equation (3), Ui is equal to the value of UAC, which is directly proportional to the intensity of the magnetic field generated by the excitation coil 10, possibly amplified by the soft-magnetic material in its vicinity. When the signal is filtered by the band-pass filter 81 set at the frequency equal to the excitation signal frequency f, the result is the signal L while according to the equation (4) its total amplitude, it means its peak-to-peak value, is equal to 2 UDC and therefore it is directly proportional to the measured external direct current magnetic field.
When the signal is filtered by the high-pass filter 82, the resulting signal U_3 corresponds only to the effects of eddy currents and therefore the proximity of object 50 made of conductive material.
Figure imgf000010_0001
UB=UAC-UDC (2)
Figure imgf000010_0002
U2(P-P)=(UA-UB)=2UDC (4)
When detecting the alternating current magnetic field, the sensor is functional already from very low frequencies where the induction-based sensors feature low sensitivity. The AMR sensor's sensitivity is frequency independent up to the frequencies below 100 kHz.
In case of conductive materials, the magnetic field penetration depth depends on the excitation field frequency. The higher the frequency, the lower the penetration depth. Using the AMR sensors as the magnetic field detector allows to use low excitation frequencies and thus increase the penetration depth. Advantageously, such sensor may be used for measuring the position of objects behind the sheath made of electrically conductive material.
As already mentioned above, in the contrary to standard solution, the proposed sensor significantly simplifies the electronic circuitry needed to evaluate the signal from the sensor. It uses the principle of self-demodulation when the magnetic field sensor's output is modulated by the identical or derived signal as the excitation coil.
Filtering the sensor output signal allows to discriminate the detected materials based on their electric and magnetic properties. This brings extra benefit in situations when the detected material is not known in advance.
Besides the proximity sensor function, this sensor works also as the position sensor detecting objects behind electrically conductive sheath. It is possible to measure position of an object made of ferromagnetic material behind an sheath made of conductive non-ferromagnetic material, such as aluminium or copper. In case the object 50, position of which is to be detected, is hidden behind a metal sheet made of magnetic material, its position may be measured when the magnetic material of the cover 70 is magnetically saturated.
The sensor measures both the direct current component of the magnetic field as well as the response of the eddy currents. Evaluation of the output signal allows to obtain the information not only about the position but also about the type of the material in proximity. The sensor's output response allows also to discriminate the detected materials as conductive, ferromagnetic or their combinations.
Using the described solution, a device shown in Fig. 3 was produced. It consists of the circular-shaped excitation coil 10 with 75 turns with the diameter of 46 mm and length of 22 mm. The excitation coil 10 is powered by the source 20 of the alternating signal by rectangular-shaped current with the amplitude of 70 mA p-p and frequency 1 kHz. Applied frequency may vary, depending on the required penetration depth. The excitation coil 10 generates around the magnetic field sensor 40, which in this case is an AMR sensor, an alternating current magnetic field with the intensity of 115 A/m. The magnetic field sensor 40 flipping is provided by the integrated coil in the magnetic field sensor 40 with pulse current 1.2 A p-p by the discharge of capacitor 30 with the capacity of 6.8 nF. Excitation modulator 30 is formed by the capacitor, which is directly connected to the excitation signal from the source 20 of the alternating signal 30 V p-p. in the center of the excitation coil 10 is located magnetic field sensor 40 l- MC1001. The output of the magnetic field sensor 40 is amplified by the amplifier 60 and subject for subsequent signal processing by individual filters.
Industrial Applicability
Sensor featuring self-demodulation may be used for detection of position/proximity of an object behind the sheath made of electrically conductive materials, such as aluminium sheet, zinc-galvanized metal sheet, etc. The sensor may be used as a position switch located behind a metal sheath or as the position switch with the closing phase detection. Advantageously, the sensor may be used as a detector of metal parts befiind the cover made of conductive materials.
Described sensor may be used for non-destructive contactless flaw detection of thickness/condition of storage tanks or piping through metal cover and insulation layer. Comparative measurements allow to determine the degree of corrosion or disruption of the inner wall.
Described sensor may be used for discrimination of materials to electrically conductive ones, soft-magnetic ones and hard-magnetic ones or their combinations. In addition, it is possible to measure the magnitude of each component and thus to estimate the proximity of an object, its position or size.

Claims

P A T E N T C L A I M S
1. Contactless magnetic sensor of the magnetic or electrically conductive objects' position consisting of at least one excitation coil (10) connected to a source (20) of the alternating excitation signal where in the cavity of the excitation coil (10) is located the magnetic field sensor (40), the output of which is connected to the input of an amplifier (60) and the output of this amplifier (60) is connected to the low-pass filter (80), to the band-pass filter (81) and to the high-pass filter (82), while it also includes an excitation modulator (21) characterized by the fact that the excitation modulator (21) of the magnetic field sensor (40) is connected to the source (20) of the alternating excitation signal of the excitation coil (10).
2. Contactless magnetic sensor according to claim 1 characterized by the fact that the source (20) of the alternating excitation signal is a source of rectangular-shaped signal.
3. Contactless magnetic sensor according to claim 1 or 2 characterized by the fact that the magnetic field sensor (40) is formed by a Hall probe.
4. Contactless magnetic sensor according to claim 1 or 2 characterized by the fact that the magnetic field sensor (40) is formed by the anisotropic magnetoresistor and the excitation modulator (21) of the magnetic field sensor (40) is formed by the separating capacitor (30) where its one terminal is connected to the flipping input of the anisotropic magnetoresistor and the other terminal is connected to the source (20) of the alternating excitation voltage of the excitation coil ( 0).
PCT/CZ2014/000117 2013-10-25 2014-10-17 Contactless magnetic sensor of the magnetic or electrically conductive objects´position Ceased WO2015058733A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CZPV2013-822 2013-10-25
CZ2013-822A CZ2013822A3 (en) 2013-10-25 2013-10-25 Contactless magnetic position sensor of magnetic or electrically conducting objects

Publications (1)

Publication Number Publication Date
WO2015058733A1 true WO2015058733A1 (en) 2015-04-30

Family

ID=51845258

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CZ2014/000117 Ceased WO2015058733A1 (en) 2013-10-25 2014-10-17 Contactless magnetic sensor of the magnetic or electrically conductive objects´position

Country Status (2)

Country Link
CZ (1) CZ2013822A3 (en)
WO (1) WO2015058733A1 (en)

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105954806A (en) * 2016-04-20 2016-09-21 上海海事大学 Metal detection method and device based on giant magnetoresistance and orthogonal bias modulation
WO2017048471A1 (en) * 2015-02-10 2017-03-23 Qualcomm Incorporated Apparatus and method for a current sensor
WO2017058586A1 (en) * 2015-09-30 2017-04-06 Allegro Microsystems, Llc Magnetic field sensors and methods using mixing in a magnetoresistance element
US9817078B2 (en) 2012-05-10 2017-11-14 Allegro Microsystems Llc Methods and apparatus for magnetic sensor having integrated coil
US10012518B2 (en) 2016-06-08 2018-07-03 Allegro Microsystems, Llc Magnetic field sensor for sensing a proximity of an object
US10145908B2 (en) 2013-07-19 2018-12-04 Allegro Microsystems, Llc Method and apparatus for magnetic sensor producing a changing magnetic field
US10310028B2 (en) 2017-05-26 2019-06-04 Allegro Microsystems, Llc Coil actuated pressure sensor
US10324141B2 (en) 2017-05-26 2019-06-18 Allegro Microsystems, Llc Packages for coil actuated position sensors
EP3521847A1 (en) * 2017-12-11 2019-08-07 Nxp B.V. Magnetoresistive sensor with stray field cancellation and systems incorporating same
US10495699B2 (en) 2013-07-19 2019-12-03 Allegro Microsystems, Llc Methods and apparatus for magnetic sensor having an integrated coil or magnet to detect a non-ferromagnetic target
US10641842B2 (en) 2017-05-26 2020-05-05 Allegro Microsystems, Llc Targets for coil actuated position sensors
US10753769B2 (en) 2014-10-31 2020-08-25 Allegro Microsystems, Llc Magnetic field sensor providing a movement detector
US10823586B2 (en) 2018-12-26 2020-11-03 Allegro Microsystems, Llc Magnetic field sensor having unequally spaced magnetic field sensing elements
US10837943B2 (en) 2017-05-26 2020-11-17 Allegro Microsystems, Llc Magnetic field sensor with error calculation
US10955306B2 (en) 2019-04-22 2021-03-23 Allegro Microsystems, Llc Coil actuated pressure sensor and deformable substrate
US10996289B2 (en) 2017-05-26 2021-05-04 Allegro Microsystems, Llc Coil actuated position sensor with reflected magnetic field
US11061084B2 (en) 2019-03-07 2021-07-13 Allegro Microsystems, Llc Coil actuated pressure sensor and deflectable substrate
CN113945608A (en) * 2021-09-30 2022-01-18 中国计量大学 Magnetic induction phase shift measurement system based on magnetoelectric sensor
US11237020B2 (en) 2019-11-14 2022-02-01 Allegro Microsystems, Llc Magnetic field sensor having two rows of magnetic field sensing elements for measuring an angle of rotation of a magnet
US11262422B2 (en) 2020-05-08 2022-03-01 Allegro Microsystems, Llc Stray-field-immune coil-activated position sensor
US11280637B2 (en) 2019-11-14 2022-03-22 Allegro Microsystems, Llc High performance magnetic angle sensor
CN114706025A (en) * 2022-04-15 2022-07-05 深圳技术大学 A resonant DC magnetic sensor based on magnetoelectric effect
US11428755B2 (en) 2017-05-26 2022-08-30 Allegro Microsystems, Llc Coil actuated sensor with sensitivity detection
US11493361B2 (en) 2021-02-26 2022-11-08 Allegro Microsystems, Llc Stray field immune coil-activated sensor
US11578997B1 (en) 2021-08-24 2023-02-14 Allegro Microsystems, Llc Angle sensor using eddy currents
JP2023124388A (en) * 2022-02-25 2023-09-06 Tdk株式会社 magnetic sensor
US12523717B2 (en) 2024-02-15 2026-01-13 Allegro Microsystems, Llc Closed loop magnetic field sensor with current control

Citations (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US484116A (en) 1892-10-11 Egon lothae schmitz
US4042876A (en) 1976-04-29 1977-08-16 The United States Of America As Represented By The United States Energy Research And Development Administration Eddy current gauge for monitoring displacement using printed circuit coil
US4140971A (en) 1977-11-10 1979-02-20 Electromagnetic Sciences, Inc. Proximity detection system utilizing a movable magnet for saturating an inductor core wherein the rise time of a plurality of such inductors are compared
US4587486A (en) 1981-12-08 1986-05-06 Werner Turck Gmbh & Co., Kg Switch for detecting a magnetic field
EP0228473A1 (en) 1985-07-03 1987-07-15 Nippon Steel Corporation Apparatus for non-destructively inspecting flaw of metal materials utilizing magnetic field
US4719362A (en) 1985-10-02 1988-01-12 Werner Turck Gmbh & Co., Kg Electronic proximity switch dependent upon a magnetic field
US5027066A (en) 1989-02-03 1991-06-25 Mannesmann Rexroth Gmbh Inductive distance sensor using a particular oscillator impedance ratio
EP0538037A2 (en) 1991-10-15 1993-04-21 Eldec Corporation Saturable core proximity sensor including a flux director
US20020130659A1 (en) 2000-11-28 2002-09-19 National Aeronautics And Space Administration Magnetoresistive flux focusing eddy current flaw detection
US6504363B1 (en) 2000-03-07 2003-01-07 Teodor Dogaru Sensor for eddy current testing and method of use thereof
JP3460363B2 (en) 1995-03-02 2003-10-27 株式会社デンソー Non-contact type position sensor
US6803757B2 (en) 2001-10-02 2004-10-12 Bentley Nevada, Llc Multi-coil eddy current proximity probe system
WO2007095971A1 (en) * 2006-02-24 2007-08-30 Commissariat A L'energie Atomique Method and device for non destructive evaluation of defects in a metallic object
US20080211492A1 (en) * 2005-03-14 2008-09-04 National University Corporation Okayama University Magnetic Impedance Measurement Device
US20120019236A1 (en) * 2010-07-26 2012-01-26 Radiation Monitoring Devices, Inc. Eddy current detection
US20120274319A1 (en) 2011-04-28 2012-11-01 U.S.A. As Represented By The Administrator Of The National Aeronautics And Space Administration Eddy Current Probe for Surface and Sub-Surface Inspection
US20130229174A1 (en) 2012-03-01 2013-09-05 Atlas Elektronik Gmbh Proximity Sensor and Method For Determining The Proximity To An Electrically Conductive Body

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0785074B2 (en) * 1990-11-22 1995-09-13 東京瓦斯株式会社 Metal flaw detector

Patent Citations (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US484116A (en) 1892-10-11 Egon lothae schmitz
US4042876A (en) 1976-04-29 1977-08-16 The United States Of America As Represented By The United States Energy Research And Development Administration Eddy current gauge for monitoring displacement using printed circuit coil
US4140971A (en) 1977-11-10 1979-02-20 Electromagnetic Sciences, Inc. Proximity detection system utilizing a movable magnet for saturating an inductor core wherein the rise time of a plurality of such inductors are compared
US4587486A (en) 1981-12-08 1986-05-06 Werner Turck Gmbh & Co., Kg Switch for detecting a magnetic field
EP0228473A1 (en) 1985-07-03 1987-07-15 Nippon Steel Corporation Apparatus for non-destructively inspecting flaw of metal materials utilizing magnetic field
US4719362A (en) 1985-10-02 1988-01-12 Werner Turck Gmbh & Co., Kg Electronic proximity switch dependent upon a magnetic field
US5027066A (en) 1989-02-03 1991-06-25 Mannesmann Rexroth Gmbh Inductive distance sensor using a particular oscillator impedance ratio
EP0538037A2 (en) 1991-10-15 1993-04-21 Eldec Corporation Saturable core proximity sensor including a flux director
JP3460363B2 (en) 1995-03-02 2003-10-27 株式会社デンソー Non-contact type position sensor
US6504363B1 (en) 2000-03-07 2003-01-07 Teodor Dogaru Sensor for eddy current testing and method of use thereof
US20020130659A1 (en) 2000-11-28 2002-09-19 National Aeronautics And Space Administration Magnetoresistive flux focusing eddy current flaw detection
US6888346B2 (en) 2000-11-28 2005-05-03 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Magnetoresistive flux focusing eddy current flaw detection
US6803757B2 (en) 2001-10-02 2004-10-12 Bentley Nevada, Llc Multi-coil eddy current proximity probe system
US20080211492A1 (en) * 2005-03-14 2008-09-04 National University Corporation Okayama University Magnetic Impedance Measurement Device
WO2007095971A1 (en) * 2006-02-24 2007-08-30 Commissariat A L'energie Atomique Method and device for non destructive evaluation of defects in a metallic object
US20120019236A1 (en) * 2010-07-26 2012-01-26 Radiation Monitoring Devices, Inc. Eddy current detection
US20120274319A1 (en) 2011-04-28 2012-11-01 U.S.A. As Represented By The Administrator Of The National Aeronautics And Space Administration Eddy Current Probe for Surface and Sub-Surface Inspection
US20130229174A1 (en) 2012-03-01 2013-09-05 Atlas Elektronik Gmbh Proximity Sensor and Method For Determining The Proximity To An Electrically Conductive Body

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
O. POSTOLACHE ET AL: "Detection and characterization of defects using GMR probes and artificial neural networks", COMPUTER STANDARDS & INTERFACES, vol. 33, no. 2, 1 February 2011 (2011-02-01), pages 191 - 200, XP055163965, ISSN: 0920-5489, DOI: 10.1016/j.csi.2010.06.011 *
RIPKA P.: "Magnetic Sensors and Magnetometers", ARTECH HOUSE PUBLISHING
TUMANSKI S: "Thin film magnetoresistive sensors", vol. 13, IOP, pages: 978 - 07503070
VYHNANEK J ET AL: "Low frequency noise of anisotropic magnetoresistors in DC and AC-excited metal detectors", JOURNAL OF PHYSICS: CONFERENCE SERIES, INSTITUTE OF PHYSICS PUBLISHING, BRISTOL, GB, vol. 450, no. 1, 26 June 2013 (2013-06-26), pages 12031, XP020246630, ISSN: 1742-6596, DOI: 10.1088/1742-6596/450/1/012031 *

Cited By (41)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9817078B2 (en) 2012-05-10 2017-11-14 Allegro Microsystems Llc Methods and apparatus for magnetic sensor having integrated coil
US11680996B2 (en) 2012-05-10 2023-06-20 Allegro Microsystems, Llc Methods and apparatus for magnetic sensor having integrated coil
US10495699B2 (en) 2013-07-19 2019-12-03 Allegro Microsystems, Llc Methods and apparatus for magnetic sensor having an integrated coil or magnet to detect a non-ferromagnetic target
US10670672B2 (en) 2013-07-19 2020-06-02 Allegro Microsystems, Llc Method and apparatus for magnetic sensor producing a changing magnetic field
US11313924B2 (en) 2013-07-19 2022-04-26 Allegro Microsystems, Llc Method and apparatus for magnetic sensor producing a changing magnetic field
US12061246B2 (en) 2013-07-19 2024-08-13 Allegro Microsystems, Llc Method and apparatus for magnetic sensor producing a changing magnetic field
US10145908B2 (en) 2013-07-19 2018-12-04 Allegro Microsystems, Llc Method and apparatus for magnetic sensor producing a changing magnetic field
US11307054B2 (en) 2014-10-31 2022-04-19 Allegro Microsystems, Llc Magnetic field sensor providing a movement detector
US10753769B2 (en) 2014-10-31 2020-08-25 Allegro Microsystems, Llc Magnetic field sensor providing a movement detector
WO2017048471A1 (en) * 2015-02-10 2017-03-23 Qualcomm Incorporated Apparatus and method for a current sensor
US9958480B2 (en) 2015-02-10 2018-05-01 Qualcomm Incorporated Apparatus and method for a current sensor
JP2018531383A (en) * 2015-09-30 2018-10-25 アレグロ・マイクロシステムズ・エルエルシー Magnetic field sensor and method using mixing in magnetoresistive elements
US10078117B2 (en) 2015-09-30 2018-09-18 Allegro Microsystems, Llc Magnetic field sensors and methods using mixing in a magnetoresistance element
WO2017058586A1 (en) * 2015-09-30 2017-04-06 Allegro Microsystems, Llc Magnetic field sensors and methods using mixing in a magnetoresistance element
CN105954806A (en) * 2016-04-20 2016-09-21 上海海事大学 Metal detection method and device based on giant magnetoresistance and orthogonal bias modulation
US10012518B2 (en) 2016-06-08 2018-07-03 Allegro Microsystems, Llc Magnetic field sensor for sensing a proximity of an object
US11320496B2 (en) 2017-05-26 2022-05-03 Allegro Microsystems, Llc Targets for coil actuated position sensors
US10324141B2 (en) 2017-05-26 2019-06-18 Allegro Microsystems, Llc Packages for coil actuated position sensors
US10310028B2 (en) 2017-05-26 2019-06-04 Allegro Microsystems, Llc Coil actuated pressure sensor
US10837943B2 (en) 2017-05-26 2020-11-17 Allegro Microsystems, Llc Magnetic field sensor with error calculation
US11768256B2 (en) 2017-05-26 2023-09-26 Allegro Microsystems, Llc Coil actuated sensor with sensitivity detection
US10996289B2 (en) 2017-05-26 2021-05-04 Allegro Microsystems, Llc Coil actuated position sensor with reflected magnetic field
US10649042B2 (en) 2017-05-26 2020-05-12 Allegro Microsystems, Llc Packages for coil actuated position sensors
US11073573B2 (en) 2017-05-26 2021-07-27 Allegro Microsystems, Llc Packages for coil actuated position sensors
US11428755B2 (en) 2017-05-26 2022-08-30 Allegro Microsystems, Llc Coil actuated sensor with sensitivity detection
US10641842B2 (en) 2017-05-26 2020-05-05 Allegro Microsystems, Llc Targets for coil actuated position sensors
US10591320B2 (en) 2017-12-11 2020-03-17 Nxp B.V. Magnetoresistive sensor with stray field cancellation and systems incorporating same
EP3521847A1 (en) * 2017-12-11 2019-08-07 Nxp B.V. Magnetoresistive sensor with stray field cancellation and systems incorporating same
US10823586B2 (en) 2018-12-26 2020-11-03 Allegro Microsystems, Llc Magnetic field sensor having unequally spaced magnetic field sensing elements
US11061084B2 (en) 2019-03-07 2021-07-13 Allegro Microsystems, Llc Coil actuated pressure sensor and deflectable substrate
US10955306B2 (en) 2019-04-22 2021-03-23 Allegro Microsystems, Llc Coil actuated pressure sensor and deformable substrate
US11237020B2 (en) 2019-11-14 2022-02-01 Allegro Microsystems, Llc Magnetic field sensor having two rows of magnetic field sensing elements for measuring an angle of rotation of a magnet
US11280637B2 (en) 2019-11-14 2022-03-22 Allegro Microsystems, Llc High performance magnetic angle sensor
US11262422B2 (en) 2020-05-08 2022-03-01 Allegro Microsystems, Llc Stray-field-immune coil-activated position sensor
US11493361B2 (en) 2021-02-26 2022-11-08 Allegro Microsystems, Llc Stray field immune coil-activated sensor
US11578997B1 (en) 2021-08-24 2023-02-14 Allegro Microsystems, Llc Angle sensor using eddy currents
CN113945608A (en) * 2021-09-30 2022-01-18 中国计量大学 Magnetic induction phase shift measurement system based on magnetoelectric sensor
JP2023124388A (en) * 2022-02-25 2023-09-06 Tdk株式会社 magnetic sensor
CN114706025A (en) * 2022-04-15 2022-07-05 深圳技术大学 A resonant DC magnetic sensor based on magnetoelectric effect
CN114706025B (en) * 2022-04-15 2024-03-22 深圳技术大学 Resonant DC magnetic sensor based on magneto-electric effect
US12523717B2 (en) 2024-02-15 2026-01-13 Allegro Microsystems, Llc Closed loop magnetic field sensor with current control

Also Published As

Publication number Publication date
CZ304954B6 (en) 2015-02-04
CZ2013822A3 (en) 2015-02-04

Similar Documents

Publication Publication Date Title
WO2015058733A1 (en) Contactless magnetic sensor of the magnetic or electrically conductive objects´position
CN102759567B (en) The EDDY CURRENT identification of steel pipe inside and outside wall defect and evaluation method under DC magnetization
CN102590328B (en) Permanent magnetic and alternating current direct current composite magnetic flux leakage detecting method
Tsukada et al. Detection of inner corrosion of steel construction using magnetic resistance sensor and magnetic spectroscopy analysis
CN105911489A (en) Common source double-frequency excitation type multifunctional micro-magnetic signal synchronous detection method
JPH0854375A (en) Electromagnetic induction-type inspecting apparatus
CN106814131A (en) A kind of ferromagnetic in-plane component shallow damage magnetic launches detection method and magnetic emission detection system
GB2262346A (en) Detecting defects in steel material
CN103439405B (en) Iron core and ferrite core synthesize multifunction electric magnetic measurement sensor and detection method thereof
US5391988A (en) Method and apparatus for detecting flaws within a conductive object while cancelling the effects of variation in distance between the detection apparatus and the conductive object
JP2013101129A (en) Eddy current sensor and detection object discrimination circuit
CN102087245B (en) Electromagnetic Detection Sensor Based on Amorphous Alloy
CN213580777U (en) A cross-pulse eddy current testing probe
George et al. A combined inductive-capacitive proximity sensor and its application to seat occupancy sensing
Ripka et al. AMR proximity sensor with inherent demodulation
EP3159854B1 (en) Coin detection system
JP2016057225A (en) Eddy current flaw detection sensor device
JP2015133397A (en) Magnetic sensor element using magneto impedance
JPH0784021A (en) Weak magnetic measurement device and nondestructive inspection method using the same
JP5209994B2 (en) Eddy current sensor
JP3942165B2 (en) Eddy current testing probe
RU2046379C1 (en) Method and apparatus for magnetic objects detection
CN203414440U (en) Multifunctional electromagnetic detection sensor synthesized through iron core and ferrite core
JP2006343300A (en) Eddy current detector
CN103954682A (en) Method for detecting discontinuity of nonmetal material by virtue of inductance of shunt-resonant circuit

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 14792726

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 14792726

Country of ref document: EP

Kind code of ref document: A1