WO2012149958A1 - Procédé de détermination d'une variation d'une valeur de capacité d'un composant capacitif, et dispositif correspondant - Google Patents

Procédé de détermination d'une variation d'une valeur de capacité d'un composant capacitif, et dispositif correspondant Download PDF

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Publication number
WO2012149958A1
WO2012149958A1 PCT/EP2011/057031 EP2011057031W WO2012149958A1 WO 2012149958 A1 WO2012149958 A1 WO 2012149958A1 EP 2011057031 W EP2011057031 W EP 2011057031W WO 2012149958 A1 WO2012149958 A1 WO 2012149958A1
Authority
WO
WIPO (PCT)
Prior art keywords
capacitance
change
capacitive component
frequency
capacitive
Prior art date
Application number
PCT/EP2011/057031
Other languages
German (de)
English (en)
Inventor
Dirk Scheibner
Arno Steckenborn
Oliver Theile
Jörg HASSEL
Original Assignee
Siemens Aktiengesellschaft
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 Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Priority to PCT/EP2011/057031 priority Critical patent/WO2012149958A1/fr
Publication of WO2012149958A1 publication Critical patent/WO2012149958A1/fr

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Classifications

    • 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
    • G01D5/24—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 capacitance
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
    • G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
    • G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
    • G01R27/2605—Measuring capacitance
    • 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
    • H03K17/955—Proximity switches using a capacitive detector

Definitions

  • the invention relates to a method for determining a change of a value of a capacitance of a capacitive Bauele ⁇ ments comprising the steps of: forming an electrical circuit comprising the capacitive component and a quartz oscillator, wherein the capacitive component acts as a load capacitance of the crystal oscillator, and placing the quartz oscillator in vibration with a first frequency.
  • the invention also relates to a device having an electrical circuit arrangement, which comprises a capacitive component and a quartz oscillator, wherein the capacitive construction ⁇ element acts as a load capacitance of the quartz oscillator, wherein the capacitive element is formed so that a value of it to its own capacity is variable ,
  • capacitive sensors where a change in a capacity as a measure to be determined measured variable is he ⁇ range covered. With such sensors, for example, distances, strains, levels or inclinations can be measured.
  • Capacitive sensors in the context of silicon micromechanics can be realized in a particularly simple and space-saving manner.
  • micromechanical force ⁇ sensors which are designed as a MEMS (microelectromechanical system) component.
  • MEMS microelectromechanical system
  • capacitance measurement can also be used as a frequency-determining element in a resonant circuit, wherein an evaluation of the oscillation frequency can be used to deduce the measuring capacitance. If the measuring frequency is known, the impedance of the capacitance can also be measured.
  • the method of charging the measuring capacitance with a constant current has the disadvantage that dynamic measurements of the change of the measuring capacity are only possible in the case of very low frequencies. For the charging time, a slight change in the measuring capacity is assumed. In this way, integration times of 100ms, for example, are just possible. For fast dynamic measurements (time ⁇ scale much smaller than 100ms), this method is therefore not suitable.
  • Oscillation frequency of the quartz oscillator from the first frequency • determining the change in the value of the capacitance of kapa ⁇ zitiven component from the deviation of the oscillation frequency ⁇ .
  • the method makes it possible to draw precise conclusions about the change in the capacitance of the capacitive component by means of frequency evaluation.
  • Crystal oscillators are inexpensive and yet allow a high-precision frequency ⁇ measurement and thus also measuring the capacitance of the capacitive device.
  • the method can be carried out in connection with a comparatively simple circuit arrangement in very compact components. By returning a capacity change to a frequency change, a highly accurate measurement method is created since times and thus frequencies can be determined with high precision.
  • the capacitive component may in particular be an electrical capacitor, in particular a plate capacitor. By the capacitive component is then provided in particular a measuring capacity whose
  • Capacity value is variable.
  • the coupling with the quartz oscillator in particular in a series circuit of capacitive component and quartz oscillator, allows the use of the so-called pulling effect for determining capacitance in the context of the method.
  • the frequency at which the crystal oscillator oscillates namely, determined by a load capacitance and thus by the capacitive component, which acts as a straight Lastkapa ⁇ capacity.
  • the capacitive component can in particular also act as trim capacitor. Changes in capacitance of the capacitive component can be caused for example by changes in a dielectric and / or distance ⁇ changes between electrodes.
  • the capacitive component or the measuring capacitance acts as a load capacitance of the quartz oscillator.
  • a change in the Lastka ⁇ capacity causes a frequency change of the quartz oscillator. This change in frequency is again a measure of the change in capacitance and of a measured variable to be determined.
  • the method comprises the following additional steps:
  • the second electrical circuit arrangement then provides, in particular, a reference system for the actually measuring electrical circuit arrangement.
  • the first means by which the Ka ⁇ capacity of the capacitive component is changed is explicitly correlated to a quantity to be measured.
  • the capacitive component is designed as a plate capacitor, wherein the first means may be to change the capacitance via a variation of the plate spacing in order to be able to infer a path change or a force change.
  • the second capacitive device detects particular exclu ⁇ Lich changes by a second agent, which also acts on the first capacitive device.
  • ⁇ tel it may order a change in an environmental ⁇ control, such as a change in temperature and / or a change in a Betauungsgrades act in particular.
  • an environmental influence can then be particularly similar to the electrical circuit arrangement and the second electrical
  • Affect circuit arrangement By means of the measuring method with the aid of the second electrical circuit arrangement, it is then ensured that these environmental influences, which cause an unintended change in capacitance at the actual measuring capacitance, can be calculated out. In this way, disturbing influences can be taken into account during the measurement process.
  • the change in the capacitance of the capacitive ⁇ tive component can be made even more precise.
  • the mixing can be effected in particular by multiplication of the two frequency signals, which in particular produces an amplitude-modulated signal whose beat can be determined.
  • a demodulation of the overall signal it is possible in particular to deduce the deviation of the oscillation frequency and consequently the change in the capacitance of the capacitive component. This type of frequency evaluation is extremely convenient, accurate and easy to perform.
  • a device comprises an electrical circuit arrangement, which comprises a capacitive component and a quartz oscillator, wherein the capacitive component ment acts as a load capacitance of the quartz oscillator, wherein the capacitive element is designed so that a value of a capacity that is its own variable.
  • the erfindungsge ⁇ Permitted device also comprises an evaluation unit which is designed to determine a conditional the capacitance of the capacitive component by a change in deviation of the oscillation frequency of the quartz oscillator of a first frequency and to determine from the change in the value of the capacitance of the capacitive component.
  • the capacitive component comprises at least two partial capacitive components, each of which acts as a load capacitance of the quartz oscillator.
  • this makes it possible to realize a differential measuring capacitance, with both partial components of the measuring capacitance in each case being able to be used as a load capacitor, and thus a significantly greater pulling effect being achievable.
  • the measuring accuracy can be increased overall. For example, lead already low ex ⁇ changes of state of the plates of a plate capacitor formed as a capacitive element in large changes in the oscillation frequency, which are easy to detect. It can be provided that the capacity change takes place in a similar manner on both partial components. However, it can also be provided that the capacity of the one sub-component decreases, while one and the same
  • the capacitive component comprises at least two units, by which an electrical capacitor is formed together, and the changing of the capacitance of the kapa ⁇ zitiven device is effected by changing a distance to ⁇ at least two units to each other.
  • the Kondensa ⁇ tor can hereby be excluded forms in particular as a plate capacitor. In this way, a highly sensitive distance measuring device is realized. Namely, the change in the distance can cause a capacitance change, which in turn leads to a frequency change on the quartz oscillator. The frequency Change is then measured and it can be deduced on the Abstandsyere ⁇ tion.
  • This embodiment also allows the realization of a device by means of which forces can be measured.
  • a force change is correlated with a change in travel via the hook's law, the change in travel being detected in turn via the capacitance and frequency change according to the present method.
  • the measuring device thus created is very universally applicable for all possible measuring processes in which a distance is to be determined.
  • a first of the at least two units as a displacement element is positionally variable relative to a second of the at least two units, and the evaluation unit is adapted to change a value of a relative distance between the first and the two from the change in the value of the capacitance of the capacitive component ⁇ th unit to determine.
  • the displacement element may in particular be a plate of a plate capacitor arranged in a positionally variable manner.
  • At least the capacitive component and the quartz oscillator are formed in a micromechanical component, in particular a silicon-based MEMS component.
  • a micromechanical component in particular a silicon-based MEMS component.
  • the apparatus comprises a second electrical circuit arrangement comprising a second capacitive Bauele ⁇ element having a capacitance whose value is known, and a second quartz oscillator, an oscillation frequency of the second crystal oscillator is determined by the capacitance of the second capacitive component, at least partially, wherein the evaluation unit is designed to change the capacitance of the capacitive component by a first and by a second means and when changing the capacitance of the second capacitive component exclusively by the Second means a portion of the change in the value of the capaci ⁇ ability of the capacitive component, which is conditioned by the first Mit ⁇ tel, from the deviation of the oscillation frequency of the quartz oscillator and a change in the Schwingungsfre- frequency of the second quartz oscillator to determine.
  • the evaluation unit is designed to change the capacitance of the capacitive component by a first and by a second means and when changing the capacitance of the second capacitive component exclusively by the Second means a portion of the change in the value of the
  • the device then comprises a housing, wherein both the electrical circuit arrangement and the second electrical circuit arrangement are formed within the housing.
  • This embodiment is particularly before ⁇ geous since it is ensured by that both the electrical circuit and second electrical circuit arrangement almost identical environmental conditions, such as temperature changes or humidity changes are exposed. Then, a very meaningful reference system is created by the second electrical scarf ⁇ tion arrangement, with which the measurement accuracy of the electrical circuit can be improved.
  • the dargestell ⁇ with reference to the inventive method ⁇ preferred embodiments and their advantages apply correspondingly for the device according to the invention.
  • 3 shows a diagram which describes the relationship between a load resonance offset and the value of a capacitance for different oscillating crystals; 4 shows an electrical circuit arrangement for a device according to a first embodiment;
  • FIG. 5 shows an electrical circuit arrangement for a device according to a second embodiment
  • the quartz crystal 3 shows a simple schematic series connection of a capacitive component, which is designed as a drawing capacitor 1 with an electrical capacitance C L , and a vibrating ⁇ quartz 3.
  • the drawing capacitor 1 acts as a load capacitance of the quartz crystal 3.
  • a change in the capacity ⁇ C L causes a change in frequency of the quartz crystal 3.
  • the frequency change in the quartz crystal 3 is thus a measure of the change in the capacitance C L of the pull capacitor 1. It is said that with the draw capacitor, the frequency of the quartz crystal 3 can be quasi pulled (so-called Ziehef- effect ).
  • the quartz crystal 3 is an electronic component, which can be described by the equivalent switching ⁇ image also shown in Figure 1 with a resonant circuit 4.
  • the oscillating circuit 4 is formed via a parallel connection of a capacitance Co and a series circuit of a capacitance Ci, a resistance Ri and an inductance Li.
  • the pull capacitor ⁇ 1 can then be the resistor R L assign, for the following applies:
  • FIG. 2 shows a circuit 2 which comprises the series circuit known from FIG.
  • the variability of the draw con- sators 1 is shown explicitly in the diagram.
  • the so-formed ⁇ series circuit is connected at its ends with an input and output of an amplifier 5, and with resistors R.
  • the effect of pulling the oscillation frequency of the quartz crystal 3 can be utilized in the measurement method.
  • a microcontroller can additionally be provided for the signal and frequency from ⁇ evaluation.
  • FIG 3 shows the so-called load resonance offset LO as a function of the capacitance C L.
  • the capacitance C L is plotted on the x-axis in picofarads, while the load resonance offset is plotted on the y-axis in parts per million.
  • the ver ⁇ different curves belong to different Co and Ci capacitance values by which FIG 1 are given replacement data for the quartz oscillator 3 according to.
  • the diagram can be read such that the load capacitance C L virtually warps the resonance frequency of the quartz crystal 3.
  • FIG. 4 a drawing capacitor 1 is likewise provided in the circuit 2, whose capacitance changes ⁇ AC L lead to frequency changes + ⁇ f on the quartz crystal 3. This frequency change + Af is made around a frequency fo.
  • circuit 2 behaves according to the circuit diagram shown in FIG. In it, however, the capacitive component of two capacitive components in the form of draw capacitors la and lb. In this way, a differential Messka ⁇ capacity is realized in which both pulling capacitors la and lb respectively used as a load capacitor of the oscillating quartz 3 ⁇ to. In this way, a larger pulling effect can be achieved, which is expressed in more pronounced frequency changes ⁇ f.
  • the drawing capacitor 1 (or la and lb) is formed as a plate capacitor, wherein one of the two plates is formed with respect to the other plate positionally variable in their distance. This movable plate is in turn connected to the system to be measured.
  • a reference quartz 3' comprising the Re ⁇ conference circuit 2 and a reference capacitor 1 'with refer- capacity C R.
  • the reference capacitor 1 ' is not formed variable, so it has a constant plate spacing.
  • the reference capacity C R is known.
  • Oscillating crystals 3 and 3 'and can be compensated so.
  • the circuits shown in Figures 2, 4, 5 and 6 are in the form of a MEMS device. This is used in the exemplary embodiment in a capacitive sensor in weighing technology. Even very slight changes in weight, which only lead to small changes in the spacing in the drawing capacitor 1, are caused by the proposed detuning of the vibration frequency. Query of the quartz crystal 3 precisely detected. There is a MEMS strain sensor created.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Oscillators With Electromechanical Resonators (AREA)

Abstract

L'invention concerne un procédé de détermination d'une variation d'une valeur de capacité (CL) d'un composant capacitif (1), comprenant les étapes suivantes : - configurer un ensemble circuit électrique (2), qui comprend le composant capacitif (CL) et un oscillateur à quartz (3), le composant capacitif (1) agissant en tant que capacité de charge de l'oscillateur à quartz (3); - amener l'oscillateur à quartz (3) en oscillation à une première fréquence (f0); - modifier la capacité (CL) du composant capacitif (1); - à une capacité modifiée (CL±ΔCL), déterminer un écart de la fréquence d'oscillation (Δf) de l'oscillateur à quartz (3) par rapport à la première fréquence (f0); et - déterminer la variation de la valeur de capacité (CL±ΔCL) du composant capacitif (1) à partir de l'écart de la fréquence d'oscillation (Δf).
PCT/EP2011/057031 2011-05-03 2011-05-03 Procédé de détermination d'une variation d'une valeur de capacité d'un composant capacitif, et dispositif correspondant WO2012149958A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2011/057031 WO2012149958A1 (fr) 2011-05-03 2011-05-03 Procédé de détermination d'une variation d'une valeur de capacité d'un composant capacitif, et dispositif correspondant

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2011/057031 WO2012149958A1 (fr) 2011-05-03 2011-05-03 Procédé de détermination d'une variation d'une valeur de capacité d'un composant capacitif, et dispositif correspondant

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WO2012149958A1 true WO2012149958A1 (fr) 2012-11-08

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2886887A1 (fr) * 2013-12-20 2015-06-24 SKF Aerospace France Dispositif pour mesurer l'usure d'un joint à rotule, joint à rotule incorporant ledit dispositif et procédé de mesure de l'usure d'une telle articulation à rotule

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2640057A1 (de) * 1975-09-10 1977-03-24 Ogasawara Geraet zum messen kleiner aenderungen
DE3138273A1 (de) * 1980-09-26 1982-10-21 Hiroomi Yamakitamachi Kanagawa Ogasawara Beruehrungsfreies mikroverschiebungs-messgeraet
EP1839911A2 (fr) * 2006-03-31 2007-10-03 Alps Electric Co., Ltd. Système de détection d'informations sur l'état d'un pneumatique
JP2008064515A (ja) * 2006-09-05 2008-03-21 Epson Toyocom Corp 圧力センサモジュール

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2640057A1 (de) * 1975-09-10 1977-03-24 Ogasawara Geraet zum messen kleiner aenderungen
DE3138273A1 (de) * 1980-09-26 1982-10-21 Hiroomi Yamakitamachi Kanagawa Ogasawara Beruehrungsfreies mikroverschiebungs-messgeraet
EP1839911A2 (fr) * 2006-03-31 2007-10-03 Alps Electric Co., Ltd. Système de détection d'informations sur l'état d'un pneumatique
JP2008064515A (ja) * 2006-09-05 2008-03-21 Epson Toyocom Corp 圧力センサモジュール

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2886887A1 (fr) * 2013-12-20 2015-06-24 SKF Aerospace France Dispositif pour mesurer l'usure d'un joint à rotule, joint à rotule incorporant ledit dispositif et procédé de mesure de l'usure d'une telle articulation à rotule
US10041529B2 (en) 2013-12-20 2018-08-07 Skf Aerospace France S.A.S. Device for measuring the wear of a ball-and-socket joint, ball-and-socket joint incorporating said device and method for measuring the wear of such a ball-and-socket joint

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