EP1007909A1 - Magnetic resonance sensor - Google Patents

Magnetic resonance sensor

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Publication number
EP1007909A1
EP1007909A1 EP96946119A EP96946119A EP1007909A1 EP 1007909 A1 EP1007909 A1 EP 1007909A1 EP 96946119 A EP96946119 A EP 96946119A EP 96946119 A EP96946119 A EP 96946119A EP 1007909 A1 EP1007909 A1 EP 1007909A1
Authority
EP
European Patent Office
Prior art keywords
sensor
magnetic
coil
magnetic field
frequency
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Withdrawn
Application number
EP96946119A
Other languages
German (de)
French (fr)
Inventor
Ralf VON SCHÄWEN
Jürgen KOBLITZ
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.)
Bic-Neisse GmbH
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Bic-Neisse GmbH
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Filing date
Publication date
Application filed by Bic-Neisse GmbH filed Critical Bic-Neisse GmbH
Publication of EP1007909A1 publication Critical patent/EP1007909A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G01V3/104—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 using several coupled or uncoupled coils
    • G01V3/105—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 using several coupled or uncoupled coils forming directly coupled primary and secondary coils or loops
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/2006—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils
    • G01D5/2013—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature by influencing the self-induction of one or more coils by a movable ferromagnetic element, e.g. a core

Definitions

  • the invention includes a magnetic field-sensitive sensor, from whose output signal with speed-independent amplitude information about the distance, the rotational speed (speed) and the direction of rotation (direction of rotation) of a magnetic field can be obtained at the same time.
  • LBE Barkhausen effect
  • the magnetic reversal takes place in a time span of approximately 50 ⁇ s, which results in a cut-off frequency of f gr ⁇ 20 kHz for the LBE. Above f Gr , sensors previously used do not generate a technically usable signal.
  • sensors with LBE materials can be divided into two classes: sensors without a magnetic excitation field and sensors with a magnetic excitation field.
  • Puls without a magnetic excitation field are also referred to as pulse wire sensors (DE Pat. No. 3729949, DE 4107847, DE 3824075, DE 3406871).
  • the BME In sensors with a magnetic excitation field, the BME is constantly magnetized again by the magnetic field of an excitation coil with the excitation frequency f Err ⁇ , the condition for the occurrence of the LBE f Err ⁇ f Gr again having to be observed for the excitation frequency.
  • Sensors with a magnetic excitation field contain a sensor coil.
  • the voltage U s induced in this sensor coil has voltage peaks due to the magnetic reversal of the BME in each half-wave.
  • An external magnetic field can either amplify or weaken the voltage peaks in each half-wave of the sensor signal depending on the orientation of the external magnetic field.
  • the operating point of the sensors can be set by superimposing a constant magnetic field on an operating point coil (DE 3241018, DE 3718857, DE 4037052, DE 421358).
  • the function of the magnetic resonance sensor differs from other magnetic field-sensitive sensors, which also use an oscillating circuit (DE 8227446, DE 8316996, DE 8517733, DE 9010779, DE 9412765), through the use of a BME as the core of the sensor coil and the possibility of simultaneous speed as well as measuring the direction of rotation and distance of the magnetic field from the sensor.
  • an oscillating circuit DE 8227446, DE 8316996, DE 8517733, DE 9010779, DE 9412765
  • the aim of the invention is to develop a sensor whose operating frequency clearly exceeds the limit frequency f Gr of the magnetic sensors with BME as the core, which is shown in the prior art, and whose output signal simultaneously contains information about the distance, speed and direction of rotation of the magnetic field. Since the limit frequency f Gr of the LBE is determined by objective physical processes, a different physical principle must be used for the sensor function.
  • the object is achieved according to the invention by the magnetic resonance sensor and a method for detecting the position and change in position of objects interacting with magnetic fields (FIG. 1).
  • the resonator system (sensor) consists of
  • a bistable magnetic core (1) at least one excitation coil (3),
  • a means for generating a magnetic field consisting either of a permanent magnet and / or a coil,
  • a high-frequency resonant circuit made up of at least one sensor coil (5) and at least one capacitor (6).
  • the high-frequency generator (2) feeds an advantageously sinusoidal AC voltage of the constant ampute voltage U and the constant resonance frequency f Res of the high-frequency resonant circuit into the excitation coil (3). As long as an outside
  • the excitation coil induces via the bistable one magnetic core (1) in the sensor coil a periodic voltage of constant amplitude and the same frequency.
  • a periodic voltage of the resonance frequency f Res with constant amplitude U s is taken off as a sensor output voltage via the high-frequency resonant circuit. The amplitude of the
  • Sensor output voltage is determined by the amplitude U Err of the high-frequency generator (2) and the operating point of the sensor.
  • This operating point can be determined by at least one of the following means: a) permanent magnet,
  • Peak amplitude of the pulse U p is independent of the change over time
  • the pulse width is proportional to the length of time that the value H Schw is exceeded or undershot.
  • the sensor function is based on the following physical processes:
  • the magnetic domains of the LBE materials are also exposed to the force of the excitation magnetic field with high-frequency external excitation magnetic fields with f Err > f Gr .
  • the domains cannot change their orientation completely, but start to oscillate at the frequency f Err due to their preferred orientation. This collective effect can still be observed at f Err > 1 MHz.
  • the vibration behavior is significantly worse because the domains interfere with each other.
  • the collective oscillation of the magnetic domains in LBE materials leads to an oscillation of the magnetic flux density B with the frequency f Err .
  • the resonance the changes in the signal of the sensor coil are amplified in such a way that they can be evaluated by measurement.
  • the sensor If no external magnetic field acts on the sensor, it delivers a periodic output signal of constant basic amplitude U G with the resonance frequency f Res of the resonant circuit integrated in the sensor.
  • the sensor When exposed to a magnetic field with the field strength H at the sensor location, where H must be greater than a threshold field strength H Scnw that is characteristic of the sensor core , the sensor delivers a pulse signal with exponential edges and the peak amplitude U P for the duration of the exposure to the magnetic field.
  • the speed can be determined from the width of the envelope of the pulse signal, and the distance from the sensor to the center of the magnetic field can be determined from the peak amplitude.
  • the magnetic resonance sensor can be used as a sensor for non-contact speed, direction of rotation and distance measurements as well as for the simultaneous measurement of speed, direction of rotation and distance. Distance, direction of rotation and speed measurements can be carried out using non-magnetic materials with a total thickness of over 5 cm. The total thickness of the non-magnetic materials can be made up of several components (e.g. aluminum housing and oil bath). Speeds up to n ⁇ 10 4 / min common in machine and engine construction can be measured.
  • the sensor can also be used under harsh environmental conditions (eg contamination of the surfaces) where optical sensors are no longer functional. Appropriate constructive measures in the design of the control magnetic field also allow angles of rotation to be measured.
  • the senor compared to pulse wire sensors are the significantly higher working frequency of the sensor, which is not limited by the LBE.
  • the sensor does not require a reset magnetic field.
  • its response time to an external magnetic field can be significantly lower than that for the
  • the invention is also characterized by the higher one
  • the width of the peak signal is inversely proportional to the speed. Therefore, the instantaneous speed can be determined from the width of the peak signal, while in the case of sensors based on the LBE, the speed can only be measured from the chronological sequence of two peaks, which corresponds to an averaging. Best way to carry out the invention
  • Figure 1 shows the circuit diagram of the arrangement according to the invention.
  • the magnetic resonance sensor consists of an excitation coil, a sensor coil and a common core that contains a mechanically fixed BME.
  • the excitation and sensor coils are arranged on the common core so that the excitation coil induces a signal in the sensor coil with a basic amplitude of approximately 3V - 5V.
  • the working point of the sensor can be determined by a working point coil also arranged on the common core, but the sensor can also function without an working point coil.
  • the inductance L s of the sensor coil is determined by the coil structure.
  • a possible design variant of the sensor coil is a cylindrical coil with 1000 windings of a copper wire with 0.1 mm diameter for
  • the inductance of the sensor coil should be between 1mH and 10 mH.
  • the capacitance of the capacitor in the resonant circuit depends on the desired resonant frequency f Res of the sensor and is based on the resonant circuit formula by W.
  • the design of the excitation coil depends on the desired output voltage of the sensor. This is determined by the turns ratio n Err / n s of the excitation coil and the sensor coil.
  • the sinusoidal excitation voltage U Err with the excitation frequency f Err is generated by a high-frequency generator.
  • the time-constant amplitude of the excitation voltage should be in the range 5V -12 V.
  • the sensor output signal must be processed electronically. Demodulation, peak detection and the evaluation of one or more threshold values are possible.

Abstract

The invention relates to a sensor sensitive to a magnetic field, the output signal of which makes it possible to obtain simultaneously information about the distance, rotational speed (number of rotations) and direction of rotation of a magnetic field. The magnetic field can be generated by a permanent magnet and/or by the action of an electric current. The aim of the invention is to develop a sensor, the operating frequency of which markedly exceeds the state-of-the-art cut-off frequency fGr for magnetic sensors having bistable magnetic elements (BME) as core, and whose output signal simultaneously contains information about the distance, number of rotations and direction of rotation of a magnetic field. Since the cut-off frequency fGr of the large Barkhausen effect (LBE) is determined by objective physical processes, a different principle of physics must be used for the sensor function described in the present invention. The magnetic resonance sensor differs in its function from other sensors sensitive to magnetic fields, which also utilize a resonant circuit, in that it uses a BME as core of the sensor coil and that it offers the possibility to measure simultaneously the number of rotations, distance and direction of rotation.

Description

Beschreibung der Erfindung Description of the invention
Magnetischer ResonanzsensorMagnetic resonance sensor
Technisches GebietTechnical field
Die Erfindung beeinhaltet einen magnetfeldempfindlichen Sensor, aus dessen Ausgangssignal mit drehzahlunabhängiger Amplitude gleichzeitig Informationen über den Abstand, die Rotationsgeschwindigkeit (Drehzahl) und die Rotationsrichtung (Drehrichtung) eines Magnetfeldes gewonnen werden können.The invention includes a magnetic field-sensitive sensor, from whose output signal with speed-independent amplitude information about the distance, the rotational speed (speed) and the direction of rotation (direction of rotation) of a magnetic field can be obtained at the same time.
Stand der TechnikState of the art
Bisher eingesetzte magnetische Sensoren mit drehzahlunabhängiger Ausgangsspannung beruhen auf dem großen Barkhausen-Effekt (engl. large Barkhausen effect ; Abkürzung in der englischsprachigen Literatur: LBE ). Beim LBE handelt es sich um eine impulsartige vollständige Ummagnetisierung spezieller magnetischer Werkstoffe, die aufgrund ihrer Zusammensetzung und des Herstellungsverfahrens eine Vorzugsausrichtung der magnetischen Domänen besitzen. Da für die Vorzugsausrichtung der magnetischen Domänen zwei stabile Zustände existieren, werden Bauteile aus LBE-Materialien auch als bistabiies magnetisches Element (nachfolgend BME abgekürzt) bezeichnet.Previously used magnetic sensors with speed-independent output voltage are based on the large Barkhausen effect (abbreviation in the English-language literature: LBE). The LBE is a pulse-like complete remagnetization of special magnetic materials that, due to their composition and the manufacturing process, have a preferred orientation of the magnetic domains. Since two stable states exist for the preferred alignment of the magnetic domains, components made of LBE materials are also referred to as bistable magnetic elements (hereinafter abbreviated BME).
Die Ummagnetisierung läuft in einer Zeitspanne von etwa 50 μ s ab, woraus sich für den LBE eine Grenzfrequenz von fGr « 20 kHz ergibt. Oberhalb von fGr generieren bisher gebräuchliche Sensoren kein technisch verwertbares Signal.The magnetic reversal takes place in a time span of approximately 50 μs, which results in a cut-off frequency of f gr <20 kHz for the LBE. Above f Gr , sensors previously used do not generate a technically usable signal.
Da die Ummagnetisierung in LBE-Werkstoffen immer impulsartig stattfindet, wenn ein äußeres Magnetfeld eine Frequenz f < fGr besitzt, ist dieser Effekt für die Nutzung in magnetischen Sensoren geeignet. Bisher gebräuchliche Sensoren mit LBE-Werkstoffen lassen sich in zwei Klassen einteilen: Sensoren ohne magnetisches Erregerfeld und Sensoren mit magnetischem Erregerfeld.Since the remagnetization in LBE materials always takes place in a pulse-like manner when an external magnetic field has a frequency f <f Gr , this effect is suitable for use in magnetic sensors. Previously used sensors with LBE materials can be divided into two classes: sensors without a magnetic excitation field and sensors with a magnetic excitation field.
Sensoren ohne magnetisches Erregerfeld werden auch als Impulsdrahtsensoren (DE Pat.-Nr. 3729949, DE 4107847, DE 3824075, DE 3406871) bezeichnet. Durch die Kopplung von Impulsdrahtsensoren mit Auswerteelektronik könnenSensors without a magnetic excitation field are also referred to as pulse wire sensors (DE Pat. No. 3729949, DE 4107847, DE 3824075, DE 3406871). By coupling pulse wire sensors with evaluation electronics
Drehzahlmeßeinrichtungen (DE 9014753, DE 3112709) realisiert werden.Speed measuring devices (DE 9014753, DE 3112709) can be realized.
Durch die Verbindung des LBE mit anderen physikalischen Wirkprinzipien ist eine größere Anzahl von Sensoren bzw. Vorrichtungen zum Patent angemeldet worden (DE 3817704, DE 3008581 , DE 3008582, DE 3046804, DE 3008526, DE 3008527, DE 3008560, DE 3008561 , DE 3008562, DE 3008581 , DE 3008582, DE 3008583, DE 3225499, DE 3225500, DE 342419, DE 3427582, DE 3637320, DE 3538514). Alle patentierten Lösungen weisen jedoch die Gemeinsamkeit auf, daß sie auf dem vollständigen Ablauf des LBE, d.h. der vollständigen Ummagnetisierung beruhen und damit nur bis zur Grenzfrequenz fGr des LBE einsatzfähig sind.By connecting the LBE with other physical principles of operation, a larger number of sensors or devices have been registered for a patent (DE 3817704, DE 3008581, DE 3008582, DE 3046804, DE 3008526, DE 3008527, DE 3008560, DE 3008561, DE 3008562, DE 3008581, DE 3008582, DE 3008583, DE 3225499, DE 3225500, DE 342419, DE 3427582, DE 3637320, DE 3538514). However, all of the patented solutions have in common that they are based on the complete sequence of the LBE, ie the complete reversal of magnetism, and can therefore only be used up to the limit frequency f Gr of the LBE.
In Sensoren mit magnetischem Erregerfeld erfolgt eine ständige Ummagnetisierung der BME durch das Magnetfeld einer Erregerspule mit der Erregerfrequenz fErr ι wobei für die Erregerfrequenz wiederum die Bedingung für das Auftreten des LBE fErr < fGr einzuhalten ist. Sensoren mit magnetischem Erregerfeld enthalten eine Sensorspule. Die in dieser Sensorspule induzierte Spannung Us besitzt Spannungsspitzen infolge der Ummagnetisierung der BME in jeder Halbwelle . Durch ein äußeres Magnetfeld können die Spannungsspitzen in jeder Halbwelle des Sensorsignals je nach Orientierung des äußeren Magnetfeldes entweder verstärkt oder abgeschwächt werden. Durch die Überlagerung eines konstanten Magnetfeldes einer Arbeitspunktspule kann der Arbeitspunkt der Sensoren eingestellt werden (DE 3241018, DE 3718857, DE 4037052, DE 421358).In sensors with a magnetic excitation field, the BME is constantly magnetized again by the magnetic field of an excitation coil with the excitation frequency f Err ι , the condition for the occurrence of the LBE f Err <f Gr again having to be observed for the excitation frequency. Sensors with a magnetic excitation field contain a sensor coil. The voltage U s induced in this sensor coil has voltage peaks due to the magnetic reversal of the BME in each half-wave. An external magnetic field can either amplify or weaken the voltage peaks in each half-wave of the sensor signal depending on the orientation of the external magnetic field. The operating point of the sensors can be set by superimposing a constant magnetic field on an operating point coil (DE 3241018, DE 3718857, DE 4037052, DE 421358).
Der magnetische Resonanzsensor unterscheidet sich in seiner Funktion von anderen magnetfeldempfindlichen Sensoren, die ebenfals einen Schwingkreis einsetzen (DE 8227446, DE 8316996, DE 8517733, DE 9010779, DE 9412765), durch die Nutzung eines BME als Kern der Sensorspule und die Möglichkeit, gleichzeitig Drehzahl sowie Drehrichtung und Abstand des Magnetfeldes zum Sensor zu messen. Darstellunα der ErfindungThe function of the magnetic resonance sensor differs from other magnetic field-sensitive sensors, which also use an oscillating circuit (DE 8227446, DE 8316996, DE 8517733, DE 9010779, DE 9412765), through the use of a BME as the core of the sensor coil and the possibility of simultaneous speed as well as measuring the direction of rotation and distance of the magnetic field from the sensor. Representation of the invention
Ziel der Erfindung ist es, einen Sensor zu entwickeln, dessen Arbeitsfrequenz die im Stand der Technik ausgewiesene Genzfrequenz fGr der magnetischen Sensoren mit BME als Kern deutlich überschreitet und dessen Ausgangssignal gleichzeitig Informationen über Abstand, Drehzahl und Drehrichtung des Magnetfeldes enthält. Da die Grenzfrequenz fGr des LBE durch objektive physikalische Prozesse festgelegt ist, muß für die Sensorfunktion ein anderes physikalisches Prinzip genutzt werden. Die Aufgabe wird erfindungsgemäß durch den magnetischen Resonanzsensor und ein Verfahren zur Detektion der Lage und Lageänderung von mit Magnetfeldern wechselwirkenden Objekten realisiert (Fig. 1).The aim of the invention is to develop a sensor whose operating frequency clearly exceeds the limit frequency f Gr of the magnetic sensors with BME as the core, which is shown in the prior art, and whose output signal simultaneously contains information about the distance, speed and direction of rotation of the magnetic field. Since the limit frequency f Gr of the LBE is determined by objective physical processes, a different physical principle must be used for the sensor function. The object is achieved according to the invention by the magnetic resonance sensor and a method for detecting the position and change in position of objects interacting with magnetic fields (FIG. 1).
Das Resonatorsystem (Sensor) besteht ausThe resonator system (sensor) consists of
• einem bistabilen magnetischen Kern (1) • mindestens einer Erregerspule (3),A bistable magnetic core (1) at least one excitation coil (3),
• einem zur Erzeugung eines Magnetfeldes dienenden Mittel, bestehend entweder aus einem Permanentmagneten oder/und einer Spule,A means for generating a magnetic field, consisting either of a permanent magnet and / or a coil,
• einem Hochfrequenzschwingkreis , aufgebaut aus mindestens einer Sensorspule (5) und mindestens einem Kondensator (6).• A high-frequency resonant circuit, made up of at least one sensor coil (5) and at least one capacitor (6).
Zum Betreiben des Sensors sind außerdem erforderlichAlso required to operate the sensor
• ein Hochfrequenzgenerator (2)• a high frequency generator (2)
• eine Gleichspannungsquelle (8)• a DC voltage source (8)
• eine Auswerteelektronik (7).• evaluation electronics (7).
Der Hochfrequenzgenarator (2) speist eine vorteilhaft sinusförmige Wechselspannung der konstanten Ampiltude U und der konstanten Resonanzfrequenz f Res des Hochfrequenzschwingkreises in die Erregerspule (3) ein. Solange ein äußeresThe high-frequency generator (2) feeds an advantageously sinusoidal AC voltage of the constant ampute voltage U and the constant resonance frequency f Res of the high-frequency resonant circuit into the excitation coil (3). As long as an outside
Magnetfeld am Sensorort eine für den Sensor charakteristische Schwellwertfeld- stärke HSchw nicht erreicht hat, induziert die Erregerspule über den bistabilen magnetischen Kern (1) in der Sensorspule eine periodische Spannung konstanter Amplitude und gleicher Frequenz. Über dem Hochfrequenzschwingkreis wird eine periodische Spannung der Resonanzfrequenz fRes mit konstanter Amplitude Us als Sensorausgangsspannung abgenommen. Die Amplitude derIf the magnetic field at the sensor location has not reached a threshold value strength H Schw which is characteristic of the sensor, the excitation coil induces via the bistable one magnetic core (1) in the sensor coil a periodic voltage of constant amplitude and the same frequency. A periodic voltage of the resonance frequency f Res with constant amplitude U s is taken off as a sensor output voltage via the high-frequency resonant circuit. The amplitude of the
Sensorausgangsspannung wird durch die Amplitude UErr des Hochfrequenzgenerators (2) und den Arbeitspunkt des Sensors festgelegt. Dieser Arbeitspunkt kann durch mindestens eines der folgenden Mittel festgelegt werden: a) Dauermagnet ,Sensor output voltage is determined by the amplitude U Err of the high-frequency generator (2) and the operating point of the sensor. This operating point can be determined by at least one of the following means: a) permanent magnet,
b) Arbeitspunktspule (4) mit anliegender Gleichspannung UDC der Gleichspannungsquelle (8) , c) Erregerspule (3) mit anliegender Gleichspannung UDC der Gleichspannungsquelle (8) .b) operating point coil (4) with applied DC voltage U DC of the DC voltage source (8), c) excitation coil (3) with applied DC voltage U DC of the DC voltage source (8).
Erreicht ein äußeres Magnetfeld den Wert Hscnw, verschiebt sich der Arbeitspunkt des Sensors in den steileren Bereich der Induktions-Feldstärke-KennlinieIf an external magnetic field reaches the value H scnw , the working point of the sensor shifts to the steeper range of the induction field strength characteristic
(B=f(H)-Kennlinie) des bistabilen magnetischen Kerns, ohne eine magnetische(B = f (H) characteristic) of the bistable magnetic core, without a magnetic one
Sättigung oder Ummagnetisierung des Kernes zu bewirken. In der Sensorspule (5) wird eine Spannung induziert, was zu einer Änderungder Amplitude derTo effect saturation or magnetic reversal of the core. A voltage is induced in the sensor coil (5), which leads to a change in the amplitude of the
Sensorausgangsspannung Us führt. Unterschreitet das Magnetfeld den Wert HSchw wieder, kehrt der Sensor in den festgelegten Arbeitspunkt zurück. Der Sensor gibt somit für die Dauer der Über- oder Unterschreitung des Wertes HSchw ein im- pulsförmiges Signal ab, welches mit der Auswerteelektronik (7) bewertet wird. DieSensor output voltage U s leads. If the magnetic field falls below the value H Schw again, the sensor returns to the specified working point. The sensor thus emits a pulse-shaped signal for the duration of the value H Schw being exceeded or undershot, which is evaluated with the evaluation electronics (7). The
Peakamplitude des Impulses Up ist unabhängig von der zeitlichen Änderung desPeak amplitude of the pulse U p is independent of the change over time
Magnetfeldes und nur abhängig von der maximalen magnetischen Feldstärke Hmax am Sensorort, die Impulsbreite ist der Zeitdauer der Über- oder Unterschreitung des Wertes HSchw proportional.Magnetic field and only dependent on the maximum magnetic field strength H max at the sensor location, the pulse width is proportional to the length of time that the value H Schw is exceeded or undershot.
Die Sensorfunktion beruht auf folgenden physikalischen Vorgängen:The sensor function is based on the following physical processes:
Die magnetischen Domänen der LBE-Werkstoffe sind auch bei hochfrequenten äußeren Erregermagnetfeldern mit fErr > fGr der Kraftwirkung des Erregermagnetfeldes ausgesetzt. Da jedoch die Periodendauer des hochfre- quenten Erregerfeldes TErr < (1/ fGr) ist, können die Domänen ihre Ausrichtung nicht vollständig ändern, sondern beginnen aufgrund ihrer Vorzugsausrichtung mit der Frequenz fErr zu schwingen. Dieser kollektive Effekt ist auch bei fErr > 1 MHz noch beobachtbar. Bei magnetischen Werkstoffen mit ungeordneter Lage der Domänen ist das Schwingungsverhalten deutlich schlechter, da sich die Domänen gegenseitig behindern. Das kollektive Schwingen der magnetischen Domänen in LBE-Werkstoffen führt zu einer Schwingung der magnetischen Flussdichte B mit der Frequenz fErr. Aufgrund des Induktionsgesetzes wird in einer Sensorspule eine periodische Spannung mit den Frequenzen n*fErr induziert . Wird am Sensorort ein zusätzliches äußeres Magnetfeld dem Erregermagnetfeld überlagert, kann sich je nach Orientierung des zusätzlichen Magnetfeldes aufgrund der dadurch bedingten Verschiebung des Arbeitspunktes des Sensors in der B = f(H) -Kennlinie des LBE- Werkstoffes die Sensorausgangsspannung Us erhöhen oder verringern. Die Änderung der Sensorausgangsspannung ist jedoch bei einem Sensor, der nur aus Erregerspule, Kern aus einem LBE-Werkstoff und Sensorspule besteht zu gering, um technisch genutzt werden zu können. Um einen meßtechnisch nutzbaren Effekt zu erzielen, muß deshalb die Sensorspule mit einem Kondensator C einen Schwingkreis bilden, dessen Resonanzfrequenz fRes = fErr ist. Durch die Nutzung der Resonanz werden die Änderungen des Signals der Sensorspule so verstärkt, daß diese meßtechnisch auswertbar werden.The magnetic domains of the LBE materials are also exposed to the force of the excitation magnetic field with high-frequency external excitation magnetic fields with f Err > f Gr . However, since the period of the high frequency quent excitation field T Err <(1 / f Gr ), the domains cannot change their orientation completely, but start to oscillate at the frequency f Err due to their preferred orientation. This collective effect can still be observed at f Err > 1 MHz. With magnetic materials with a disordered position of the domains, the vibration behavior is significantly worse because the domains interfere with each other. The collective oscillation of the magnetic domains in LBE materials leads to an oscillation of the magnetic flux density B with the frequency f Err . Due to the law of induction, a periodic voltage with the frequencies n * f Err is induced in a sensor coil. If an additional external magnetic field is superimposed on the excitation magnetic field at the sensor location, the sensor output voltage U s can increase or decrease depending on the orientation of the additional magnetic field due to the resulting shift in the working point of the sensor in the B = f (H) characteristic of the LBE material. However, the change in the sensor output voltage is too small for a sensor that consists only of the excitation coil, core of an LBE material and sensor coil to be able to be used technically. In order to achieve an effect that can be used in measurement technology, the sensor coil must therefore form a resonant circuit with a capacitor C, the resonance frequency of which is f Res = f Err . By using the resonance, the changes in the signal of the sensor coil are amplified in such a way that they can be evaluated by measurement.
Wirkt kein äußeres Magnetfeld auf den Sensor ein, liefert er ein periodisches Ausgangssignal konstanter Grundamplitude UG mit der Resonanzfrequenz fRes des im Sensor integrierten Schwingkreises. Bei Einwirkung eines Magnetfeldes mit der Feldstärke H am Sensorort, wobei H größer sein muß als eine für den Sensorkern charakteristische Schwellwertfeldstärke HScnw , liefert der Sensor für die Dauer der Einwirkung des Magnetfeldes ein Impulssignal mit exponentiellen Flanken und der Peakamplitude UP.If no external magnetic field acts on the sensor, it delivers a periodic output signal of constant basic amplitude U G with the resonance frequency f Res of the resonant circuit integrated in the sensor. When exposed to a magnetic field with the field strength H at the sensor location, where H must be greater than a threshold field strength H Scnw that is characteristic of the sensor core , the sensor delivers a pulse signal with exponential edges and the peak amplitude U P for the duration of the exposure to the magnetic field.
Aus der Breite der Hüllkurve des Impulssignais kann die Drehzahl, aus der Peakamplitude der Abstand des Sensors zum Zentrum des Magnetfeldes ermittelt werden. Der magnetische Resonanzsensor ist als Sensor für berührungslose Drehzahl-, Drehrichtungs- und Abstandsmessungen sowie für die gleichzeitige Messung von Drehzahl, Drehrichtung und Abstand einsetzbar. Abstands-, Drehrichtungs- und Drehzahlmessungen können durch nichtmagnetische Werkstoffe mit einer Gesamtdicke von über 5cm ausgeführt werden. Die Gesamtdicke der nichtmagnetischen Werkstoffe kann sich aus mehreren Komponenten zusammensetzen (z.B. Aluminiumgehäuse und Ölbad). Im Maschinen- und Motorenbau übliche Drehzahlen bis n ~ 104 / min können gemessen werden. Der Sensor ist auch unter rauhen Umweltbedingungen einsetzbar (z.B. Verschmutzung der Oberflächen), bei denen optische Sensoren nicht mehr funktionsfähig sind. Durch geeignete konstruktive Maßnahmen bei der Gestaltung des Ansteuermagnetfeldes sind auch Drehwinkel meßbar.The speed can be determined from the width of the envelope of the pulse signal, and the distance from the sensor to the center of the magnetic field can be determined from the peak amplitude. The magnetic resonance sensor can be used as a sensor for non-contact speed, direction of rotation and distance measurements as well as for the simultaneous measurement of speed, direction of rotation and distance. Distance, direction of rotation and speed measurements can be carried out using non-magnetic materials with a total thickness of over 5 cm. The total thickness of the non-magnetic materials can be made up of several components (e.g. aluminum housing and oil bath). Speeds up to n ~ 10 4 / min common in machine and engine construction can be measured. The sensor can also be used under harsh environmental conditions (eg contamination of the surfaces) where optical sensors are no longer functional. Appropriate constructive measures in the design of the control magnetic field also allow angles of rotation to be measured.
Vorteilhafte Eigenschaften des Sensors liegen gegenüber Impulsdrahtsensoren in der wesentlich höheren Arbeitsfrequenz des Sensors, die nicht durch den LBE begrenzt wird. Der Sensor benötigt im Gegensatz zu den Impulsdrahtsensoren kein Rücksetzmagnetfeld. Seine Ansprechzeit auf ein äußeres Magnetfeld kann abhängig von der Güte des Resonanzschwingkreises deutlich unter der für denAdvantageous properties of the sensor compared to pulse wire sensors are the significantly higher working frequency of the sensor, which is not limited by the LBE. In contrast to the pulse wire sensors, the sensor does not require a reset magnetic field. Depending on the quality of the resonant circuit, its response time to an external magnetic field can be significantly lower than that for the
LBE charakteristischen Zeit von 50 μs liegen. Gegenüber Sensoren mit magnetischem Erregerfeld zeichnet sich die Erfindung ebenfalls durch die höhereLBE characteristic time of 50 μs. Compared to sensors with a magnetic excitation field, the invention is also characterized by the higher one
Arbeitsfrequenz und eine einfachere Signalstruktur aus. Das mit derWorking frequency and a simpler signal structure. The one with the
Erregerfrequenz modulierte Ausgangssignal läßt sich elektronisch einfach verarbeiten. Wählt man z.B. die Erregerfrequenz fErr = 1 MHz, kann man die die für die Drehzahlmessung erforderliche Zeitmessung auf eine Auszählung der Periodenanzahl der Erregerfrequenz innerhalb der Einhüllenden des Peaksignals des Sensors zurückführen.Excitation frequency modulated output signal is easy to process electronically. For example, if the excitation frequency f Err = 1 MHz is selected, the time measurement required for the speed measurement can be traced back to a counting of the number of periods of the excitation frequency within the envelope of the peak signal of the sensor.
Bei konstantem Abstand zwischen Sensor und Zentrum des Magnetfeldes ist die Breite des Peaksignals der Drehzahl umgekehrt proportional. Deshalb kann aus der Breite des Peaksignals die Momentandrehzahl ermittelt werden, während bei Sensoren, die auf dem LBE beruhen , die Drehzahl nur aus der zeitlichen Abfolge von zwei Peaks gemessen werden kann, was einer Mittelung entspricht. Bester Weg zur Ausführung der ErfindungWith a constant distance between the sensor and the center of the magnetic field, the width of the peak signal is inversely proportional to the speed. Therefore, the instantaneous speed can be determined from the width of the peak signal, while in the case of sensors based on the LBE, the speed can only be measured from the chronological sequence of two peaks, which corresponds to an averaging. Best way to carry out the invention
Die Erfindung wird nachstehend an einem Ausführungsbeispiel näher beschrieben. Figur 1 zeigt dabei das Schaltbild der erfindungsgemäßen Anordnung. Der magnetische Resonanzsensor besteht hierbei aus einer Erregerspule , einer Sensorspule und einem gemeinsamen Kern, der ein mechanisch fixiertes BME enthält.The invention is described in more detail below using an exemplary embodiment. Figure 1 shows the circuit diagram of the arrangement according to the invention. The magnetic resonance sensor consists of an excitation coil, a sensor coil and a common core that contains a mechanically fixed BME.
Die Erreger- und Sensorspule sind so auf dem gemeinsamen Kern angeordnet, daß die Erregerspule in der Sensorspule ein Signal mit einer Grundamplitude von etwa 3V - 5V induziert.The excitation and sensor coils are arranged on the common core so that the excitation coil induces a signal in the sensor coil with a basic amplitude of approximately 3V - 5V.
Der Arbeitspunkt des Sensors kann durch eine ebenfalls auf dem gemeinsamen Kern angeordnete Arbeitspunktspule festgelegt werden, jedoch ist der Sensor auch ohne Arbeitspunktspule funktionsfähig.The working point of the sensor can be determined by a working point coil also arranged on the common core, but the sensor can also function without an working point coil.
Die Induktivität Ls der Sensorspule wird durch den Spulenaufbau festgelegt. Eine mögliche Gestaltungsvariante der Sensorspule ist eine zylindrische Spule mit 1000 Wicklungen eines Kupferdrahtes mit 0,1 mm Durchmesser FürThe inductance L s of the sensor coil is determined by the coil structure. A possible design variant of the sensor coil is a cylindrical coil with 1000 windings of a copper wire with 0.1 mm diameter for
Resonanzfrequenzen fRes zwischen 500kHz und 1MHz sollte die Induktivität der Sensorspule zwischen 1mH und 10 mH betragen.Resonance frequencies f Res between 500kHz and 1MHz, the inductance of the sensor coil should be between 1mH and 10 mH.
Die Kapazität des Kondensators im Schwingkreis hängt von der gewünschten Resonanzfrequenz fRes des Sensors ab und ist nach der Schwingkreisformel von W. ThomsonThe capacitance of the capacitor in the resonant circuit depends on the desired resonant frequency f Res of the sensor and is based on the resonant circuit formula by W. Thomson
zu dimensionieren. to dimension.
Die Gestaltung der Erregerspule richtet sich nach der gewünschten Ausgangspannung des Sensors . Diese wird durch das Windungsverhältnis nErr / ns von Erregerspule und Sensorspule festgelegt.The design of the excitation coil depends on the desired output voltage of the sensor. This is determined by the turns ratio n Err / n s of the excitation coil and the sensor coil.
Zum Schutz des Sensors muß dieser von einem Gehäuse aus einem nichtmagnetischen Werkstoff umgeben sein. Die sinusförmige Erregerspannung UErr mit der Erregerfrequenz fErr , für die gilt: fErr = fRes des Schwingkreises, wird durch einen Hochfrequenzgenerator erzeugt. Die zeitlich konstante Amplitude der Erregerspannung sollte im Bereich 5V -12 V liegen.To protect the sensor, it must be surrounded by a housing made of a non-magnetic material. The sinusoidal excitation voltage U Err with the excitation frequency f Err , for which the following applies: f Err = f Res of the resonant circuit, is generated by a high-frequency generator. The time-constant amplitude of the excitation voltage should be in the range 5V -12 V.
Das Ausgangssignal des Sensors muß elektronisch verarbeitet werden. Möglich sind Demodulation, Peakdetektion und die Auswertung eines Schwellwertes oder mehrerer Schwellwerte. The sensor output signal must be processed electronically. Demodulation, peak detection and the evaluation of one or more threshold values are possible.
Liste der verwendeten BezugszeichenList of the reference symbols used
1 bistabiler magnetischer Kern 2 Hochfrequenzgenerator1 bistable magnetic core 2 high frequency generator
3 Erregerspule3 excitation coil
4 der Erzeugung eines Magnetfeldes dienendes Mittel 4.1 Arbeitspunktspule4 means generating a magnetic field 4.1 working point coil
5 Sensorspule 6 Kondensator5 sensor coil 6 capacitor
7 Auswerteelektronik7 evaluation electronics
8 Gleichspannungsquelle 8 DC voltage source

Claims

Ansprüche Expectations
1. Magnetischer Resonanzsensor, gekennzeichnet dadurch, daß bei einem aus mindestens einer Sensorspule (5) und mindestens einem Kondensator (6) bestehenden Erreger- und Resonatorsystem vorzugsweise mit einem der Erzeugung eines Magnetfeldes dienenden Mittel (4) mindestens eine Erregerspule (3) und mindestens eine Sensorspule (5) um einen gemeinsamen, ein- oder mehrteiligen, bistabilen magnetischen Kern (1) vorzugsweise koaxial angeordnet sind.1. Magnetic resonance sensor, characterized in that in the case of an excitation and resonator system consisting of at least one sensor coil (5) and at least one capacitor (6), preferably with a means (4) for generating a magnetic field, at least one excitation coil (3) and at least one a sensor coil (5) around a common, one-part or multi-part, bistable magnetic core (1) are preferably arranged coaxially.
2. Magnetischer Resonanzsensor nach Anspruch 1 , gekennzeichnet dadurch, daß das der Erzeugung eines Magnetfeldes dienende Mittel (4) vorzugsweise als mindestens eine Arbeitspunktspule (4.1) oder/und eine Erregerspule (3) ausgebildet ist.2. Magnetic resonance sensor according to claim 1, characterized in that the means for generating a magnetic field (4) is preferably designed as at least one operating point coil (4.1) and / or an excitation coil (3).
3. Verfahren zur Detektion der Lage und Lageänderung von mit Magnetfeldern wechselwirkenden Objekten, gekennzeichnet dadurch, daß a) ein Hochfrequenzgenerator eine vorzugsweise sinusförmige Wechselspannung einer konstanten Amplitude UHF und einer konstanten3. A method for detecting the position and change of position of objects interacting with magnetic fields, characterized in that a) a high-frequency generator has a preferably sinusoidal AC voltage of a constant amplitude U HF and a constant
Resonanzfrequenz f eines aus mindestens einer Sensorspule (5) und mindestens einem Kondensator (6) bestehenden Hochfrequenzschwingkreises in eine Erregerspule (3) einspeist; b) der Arbeitspunkt eines Sensors nach den Ansprüchen 1. und 2. auf der Induktions-Feldstärke-Kennlinie (B = f(H) - Kennlinie) durch ein auf den Sensor einwirkendes Magnetfeld festgelegt wird; c) die Erregerspule (3) über einen bistabilen magnetischen Kern (1) in der Sensorspule (5) eine periodische Spannung konstanter Amplitude Usund der Frequenz n*fEπ. induziert, solange das äußere Magnetfeld am Sensorort eine für den Sensor charakteristische Schwellwertfeldstärke HScnw nicht überschreitet; d) der Sensor sich vor Erreichen einer für den Sensor charakteristischen Feldstärke HSchw im Arbeitspunkt A auf der B = f(H) - Kennlinie befindet; e) der Sensor bei Erreichen einer für den Sensor charakteristischen Feldstärke HSchw in den Arbeitspunkt B auf der B = f(H) - Kennlinie übergeht und sich dadurch die Amplitude Us der Sensorspannung und das Frequenzspektrum reproduzierbar verändern; f) der Sensor bei erneutem Erreichen der für den Sensor charakteristischen Feldstärke HSchw wieder in den Arbeitspunkt A auf der B = f(H) - Kennlinie übergeht und sich dadurch der Zustand nach Punkt d) einstellt; g) in einer Auswerteelektronik (7) die zur Detektion der Lage und Lageänderung von mit Magnetfeldern wechselwirkenden Objekten notwendigen Informationen aus der Seπsorspannung gewonnen werden. Feeds resonance frequency f of a high-frequency resonant circuit consisting of at least one sensor coil (5) and at least one capacitor (6) into an excitation coil (3); b) the working point of a sensor according to claims 1 and 2 is determined on the induction field strength characteristic (B = f (H) characteristic) by a magnetic field acting on the sensor; c) the excitation coil (3) via a bistable magnetic core (1) in the sensor coil (5) has a periodic voltage of constant amplitude U s and the frequency n * f Eπ . induced as long as the external magnetic field at the sensor location does not exceed a threshold field strength H Scnw which is characteristic of the sensor; d) the sensor is in the working point A on the B = f (H) characteristic before reaching a field strength H Schw which is characteristic of the sensor; e) the sensor changes to the working point B on the B = f (H) characteristic curve when a field strength H Schw which is characteristic of the sensor is reached, and the amplitude U s of the sensor voltage and the frequency spectrum thereby change reproducibly; f) when the field strength H Schw , which is characteristic of the sensor, is reached again, the sensor changes again into the working point A on the B = f (H) characteristic curve, and the state according to point d) is thereby established; g) in an electronic evaluation unit (7) the information necessary for the detection of the position and change of position of objects interacting with magnetic fields is obtained from the sensor voltage.
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