WO2012025417A1 - Procédé de mesure et dispositif de mesure pour acquérir une variation dans le temps d'une capacité électrique - Google Patents

Procédé de mesure et dispositif de mesure pour acquérir une variation dans le temps d'une capacité électrique Download PDF

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Publication number
WO2012025417A1
WO2012025417A1 PCT/EP2011/064035 EP2011064035W WO2012025417A1 WO 2012025417 A1 WO2012025417 A1 WO 2012025417A1 EP 2011064035 W EP2011064035 W EP 2011064035W WO 2012025417 A1 WO2012025417 A1 WO 2012025417A1
Authority
WO
WIPO (PCT)
Prior art keywords
measuring
current
resistor
capacitance
voltage
Prior art date
Application number
PCT/EP2011/064035
Other languages
German (de)
English (en)
Inventor
Jörg HASSEL
Arno Steckenborn
Oliver Theile
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
Publication of WO2012025417A1 publication Critical patent/WO2012025417A1/fr

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Classifications

    • 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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
    • G01F1/8422—Coriolis or gyroscopic mass flowmeters constructional details exciters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
    • G01F1/8427—Coriolis or gyroscopic mass flowmeters constructional details detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/78—Direct mass flowmeters
    • G01F1/80—Direct mass flowmeters operating by measuring pressure, force, momentum, or frequency of a fluid flow to which a rotational movement has been imparted
    • G01F1/84—Coriolis or gyroscopic mass flowmeters
    • G01F1/8409—Coriolis or gyroscopic mass flowmeters constructional details
    • G01F1/8431—Coriolis or gyroscopic mass flowmeters constructional details electronic circuits

Definitions

  • the invention relates to a measuring method in which the zeitli ⁇ che change of an electric capacity is detected in that a result of the change in the capacitance er Weg ⁇ ter displacement current I (t) with a measuring device is measured sen, wherein the temporal variation of the capacitance me ⁇ chanically brought about with an electric actuator.
  • the invention relates to a measuring arrangement, which is suitable for carrying out the specified measuring method, with a measuring device for measuring the temporal change of an electrical capacitance.
  • the temporal change of the capacity is caused by an electrical actuator by mechanical means.
  • the capacitance can be changed by varying the area of the associated coded plate. Another possibility is to change the distance of the capacitor plates.
  • the dielectric constant of the medium may be changed, which is located between the capacitor plates ⁇ Kon.
  • the capacitor plates do not have to be objectively formed as a flat structure. Other geometric means capable of storing electric charges may also be used.
  • an application of the measuring method or a construction of the measuring arrangement is possible, which is referred to as a field mill.
  • the measurement arrangement only one con ⁇ densatorplatte is realized, while the other capacitor plate ⁇ so to speak, formed by the environment.
  • the measuring device incorporated in the measuring device has a current-voltage converter, to the input of which a shift current I (t) generated due to the change of the capacitance is passed and a voltage signal U (t) proportional to the displacement current I (t). from the ⁇ provides transitional available.
  • the measuring arrangement given at the outset is designed, for example, as a micromechanical system and can be used as a voltmeter.
  • a capacitor plate is used, which is designed as a coating of a microelectromechanical system (MEMS).
  • MEMS microelectromechanical system
  • a movable aperture is arranged, which can be pushed over the capacitor plate and thus reduces the effec ⁇ tive capacitor area and increases.
  • This Blen ⁇ de is provided with a micromechanical drive, which consists of comb-like electrodes, which can be acted upon by a voltage. The resulting electrostatic forces cause a relative movement between the comb-like electrodes, whereby the diaphragm is moved.
  • micromechanical sensor designed as MEMS is described in DE 10 2006 029 443 B2.
  • This is a vibratory pipe system, which can be traversed by egg ⁇ nem fluid. Since the flowing fluid must be accelerated in the oscillating pipe system, this also has an effect on the vibration behavior of the pipe system.
  • the pipe system is further provided with measuring electrodes, which form a measuring capacitor. Therefore, that can initially specified measuring method for determining the vibration behavior of the pipe system can be used.
  • US Pat. No. 3,812,419 discloses an instrument for measuring the field strength, which operates on the principle of a field mill.
  • a structure having the function of a gyroscope can be manufactured as a MEMS structure.
  • One way of performing the measurement would now be to turn off the excitation during the measurement. However, it would then have to be accepted that both the excitation and the measurement would be discontinuous. In addition, the system would swing off after switching off the excitation depending on its own attenuation.
  • the object of the invention is therefore to specify a measuring method and a measuring arrangement with which or with which a continuous measurement of a change in capacitance with simultaneously comparatively low metrological complexity with comparatively high accuracy is possible.
  • the object is achieved with the measuring method given at the beginning by a combination of the following measures.
  • the first measure is that the time profile of the electrical drive voltage U (t) is selected for the actuator such that it is contained in time intervals with constant on ⁇ operating voltage in it.
  • the property of the capacitive measuring principle is taken into account by the fact that a signal can only be detected when the charge moves on the capacitor, which initiate the displacement current I (t).
  • I (t) dC / dt * U + dU / dt 'C applies, where C is the capacitance of the capacitor and U is the voltage applied to the Kon ⁇ capacitor.
  • the capacitance of the capacitor can be changed by changing the area of the capacitor plates (eg by inserting apertures in the capacitor gap), by changing the distance of the capacitor plates or by changing the relative dielectric constant of the medium between the plates.
  • the time profile of the electrical drive voltage U (t) is selected for the actuator so that time intervals are included with constant drive voltage, so in this time interval an influence due to crosstalk to ⁇ least be largely excluded, since the drive voltage does not change.
  • a drive concept with a drive voltage containing time intervals with a constant voltage value could proceed as follows. If the on ⁇ operating voltage is brought to the constant value acts an electrostatic force on each moving part of the electric actuator, which causes movement thereof.
  • Rectangular voltage are interconnected.
  • An influence on the measurement signal by the capacitive coupling, due to the design of the measuring arrangement, can therefore be reduced to the comparatively short times of passage of the switching edges.
  • the measurement intervals are completely within the time intervals of constant drive voltage and the displacement current I (t) is measured in these measurement intervals.
  • the two pulses from the differentiated switching edges of the drive voltage are in fact relatively high due to the steep signal curve in the region of the switching edges.
  • the useful signals lying the ⁇ ser pulses in the vicinity can therefore not be measured with the necessary for the dissolution of the transimpedance of the coming for use current-voltage converter, since this factor of approximately 1000 are smaller. If, however, the conversion factor of the current-voltage converter were increased as required, this would lead to unacceptable settling times after the pulse-induced overdriving of the converter.
  • the measuring device is blanked out at blanking intervals, so that the measuring device does not process the measuring signal during the blanking intervals, wherein time intervals in which the drive voltage is changed (ie in which the switch-on edges or switch-off edges of the drive voltage U (FIG. t) are located completely in the blanking intervals.
  • time intervals in which the drive voltage is changed ie in which the switch-on edges or switch-off edges of the drive voltage U (FIG. t) are located completely in the blanking intervals.
  • the gain can then be significantly increased by the current-voltage converter, without causing a large overshoot or an excessively long transient during the measurement.
  • a blanking of the measuring device is understood to mean that the measuring device does not detect the measuring signal processed.
  • the measuring device which contains the current-voltage converter, does not receive the measuring signal.
  • this would be a measure to switch off the measuring device.
  • This would make the inventively desired goal of a quasi-continuous measurement impossible, however, since the operational readiness would not manufactured in genü ⁇ quietly a short time after switching on the measuring device.
  • This is different with a blanking of the measuring device, as it remains active during the time and after the end of the blanking interval ⁇ advantageously after a relatively short time again measuring signals ver ⁇ works can be.
  • the object is achieved by the measures that the current-voltage converter has an enable input, which is connected to a control device and the controller provides an enable signal available, which activates the current-voltage converter ,
  • the enable signal can be used to realize the above-described blanking of the measuring device.
  • the enable signal activates the current-voltage converter and as soon as this signal is removed, the current-voltage converter is deactivated, but not switched off. So be ⁇ starts the blanking interval. After completion of the Austastinter ⁇ valls an enable signal by the controller is made available again.
  • the actuator is driven by electrostatic forces.
  • a drive voltage U (t) can be used which has comparatively steep switching edges, in particular a square-wave voltage, and whose time intervals are more constant Voltage are each at zero and a defined drive voltage, which provides a sufficient electrostatic force to drive the electric actuator.
  • a further advantageous embodiment of the invention is obtained if in each case between the blanking interval and the measuring interval, a reaction interval is set, in which the dead time of the measuring device due to the blanking is completely. As already mentioned, even after the termination of the blanking interval a short dead time of
  • Measuring device in particular of the current-voltage converter the result.
  • this reaction is onsintervall, in which the dead time of the measuring device is located, hidden so that the measurement interval only then be ⁇ begins ,
  • This third resistance is be ⁇ neminte at ground potential and whose resistance value is determined on the one hand by the realizable transimpedance, given by the ratio of the second resistor to third resistor ((hereinafter R2) ie by the quotient with the second abutment sand in the numerator and the third resistor in the denominator: R2 / R3), multiplied by the first resistor (hereinafter Rl) and on the other hand by the time ⁇ constant of the discharge, given by the sum of the first resistor and the third resistor (R1 + R3) mul- tiplicated with the capacitance to be measured (17), wherein the time constant of the discharging process is sufficiently small, since ⁇ is completed with the discharge in the blanking interval (a). It is particularly advantageous if the resistance of the second resistor, which is closer to the output of the current-voltage converter than the first resistor, is at most one tenth of that of the first resistor.
  • the described circuit of the resistors in the feedback line takes account of the following circumstance. Although the influence of the switching edges of the drive voltage on the signal can be suppressed by blanking. However, the drive voltage is generated charge on the measurement capacitor through the switching edges, and the associated change that must flow from ⁇ upon reconnection of the current-voltage converter only. Due to the high transimpedance of the converter in standard circuit with a high-impedance feedback resistor, however, this transient is so slow that the measurement of the very small displacement currents I (t) would still not be immediately possible. So here an electrical path is required, which quickly discharges the measuring capacitor despite high transimpedance.
  • the blanking interval and / or the at ⁇ operating voltage and / or the measurement interval can be monitored by a control device.
  • the electrical capacitance is formed by a measuring capacitor whose capacitor area is varied with the actuator.
  • the actuator pushes or pulls out a diaphragm into the capacitor gap, wherein the diaphragm leads to a partial covering of the capacitor plates, whereby the available area of the capacitor plates is changed.
  • a voltmeter can be produced, as described in the already mentioned DE 10 2008 052 477 A1.
  • the electrical capaci ⁇ ability is formed by a vibratory and a flow-through pipe system, the actuator excites the pipe system to vibrate.
  • the vibrations can also the
  • Width of a condenser gap vary between formed ⁇ torplatten or vary an overlap of these capacitor plates.
  • a capacitor plate on the movable part of the pipe system and a Plat- te attached to a stationary part of the measuring arrangement in each case a capacitor plate on the movable part of the pipe system and a Plat- te attached to a stationary part of the measuring arrangement.
  • FIG. 1 shows an exemplary embodiment of the measuring arrangement according to the invention as a block diagram
  • FIG 2 shows the waveform for one embodiment of the measuring method according to the invention, as can be generated in the pitch ⁇ with a measuring arrangement according to FIG 1,
  • Figure 3 shows another embodiment of the invention shown SEN measurement arrangement as a block diagram
  • Figure 4 shows an alternative embodiment of the measuring device according to a particular embodiment of he ⁇ inventive measuring arrangement, as this can also be used in measuring arrangements according to Figure 1 and Figure 3.
  • FIG. 1 shows a measurement arrangement 11 is illustrated which can play to be used as a voltmeter at ⁇ .
  • This measuring arrangement has three areas I, II and III, whose boundaries are indicated by dashed lines. Except- there is a region IV, which is formed by a control device (also referred to below as control) 12 for a short time.
  • control also referred to below as control
  • the region I of the actuator is shown only schematically and can be designed as in the prior art already explained above.
  • the actuator has a voltage source 13, with which a voltage U (t) can be generated which has an indicated rectangular profile.
  • the ⁇ ser due to the time-varying voltage U (t) is an alternating field strength of the electric field generated ent ⁇ with this voltage a drive capacitance 14 is fed, so that in.
  • a diaphragm 15 is arranged, which is held by an elas ⁇ diagram suspension 16, thus forming a vibrational ⁇ capable system.
  • the diaphragm 15 is displaced out of this capacitor gap and let in again, and due to the elastic suspension 16 it executes vibrations.
  • the region II of the capacitance 17 to be measured Spatially adjacent to the region I of the actuator is the region II of the capacitance 17 to be measured.
  • the capacitor plates of the capacitance 17 are arranged so that the capacitor gap formed by them lies in a plane with the capacitor gap of the drive capacitance 14. Therefore, the aperture 15, when it is pushed out of the drive capacity 14 ver ⁇ immerse in the capacitance to be measured 17 and thus change the available for the formation of the electric field surface of the capacitor plates of the capacitance 17.
  • the drive capacity 14 and the capacitance 17 to be measured also influence each other in an undesired manner. This is due to a jamming capacity 18 indicated, which of course not, as shown, is formed by a capacitor, but is determined by the design of the real measuring device.
  • the diaphragm 15 oscillates between the drive capacity 14 and the capacitance 17 to be measured.
  • the aperture is shown in the initial position in which it is completely in the Antriebskapa ⁇ capacity 14. Dashed lines the opposite position is shown, in which the aperture 15 is completely in the capacitance 17 to be measured.
  • the diaphragm allows the capacitor area of the capacitance 17 to be measured to alternate between 0 and 100% by means of a shield.
  • the size of the capacitor 17 is variable in time, so that a displacement current I (t) is produced.
  • This can be demonstrated by the arranged in the area III measuring device. This is electrically connected to one capacitor plate of the capacitance 17 and has a current-voltage converter 19 which is connected to its negative input (in) with the capacitance 17.
  • Input is connected to a DC voltage source 20.
  • the current-to-voltage converter 19 outputs at the output (out) a voltage which is proportional to the displacement current I (t).
  • This voltage M (t) can be measured with an analog-to-digital converter 21 and output to a control unit 12.
  • the feedback line leads via the feedback resistor R to the input (in) of the current-voltage converter.
  • a signal line 23 provides a connection to the voltage source 13.
  • the controller via the signal line 23 receives the course of the excitation ⁇ voltage generated by the voltage source 13 without affecting this itself.
  • the voltage source 13 is driven, so that the time ⁇ Liche voltage curve U (t) can be determined by the controller.
  • the time profile of the drive voltage U (t) must be taken into account in order to generate an enable signal E (t).
  • This is fed via a Signallei ⁇ tung 24 in a control input (enable) of the current-voltage transducer and here a blanking interval he attests ⁇ (this hereinafter more).
  • the current-to-voltage converter is always blanked when the enable signal E (t) deactivates it.
  • FIG. 2 shows the time profile of the excitation voltage U (t), the enable signal E (t) and the measurement signal M (t) over time. In the areas where the displacement ⁇ current I (t) of the measurement signal M (t) deviates, the course of the displacement current is shown in phantom.
  • the measurement signal M (t) is equal to zero, which is achieved by setting the enable signal E (t) to zero for the time of the blanking interval. In this way, wherein it is turned on again at the end of the blanking interval a, it is achieved that does not occur in the current-voltage converter to a crosstalk when the impulse response of the displacement current I (t) is already largely be ⁇ subsided.
  • the current-voltage converter 19 requires a certain reaction time after activation of the enable signal. This is in the reaction interval r, which is taken into account in the controller 12, so that no measuring points A can be placed in this time interval. Only then does the measuring interval m start, in which the measuring signal M (t) can be sampled to generate measured values (see points A in FIG. The measurement interval m ending with the beginning of the next blanking interval a, whose position in time is determined by that due time before He 26 ⁇ rich the next switching edge of the drive voltage U (t) of the current-voltage converter 19 must be deactivated.
  • the measuring arrangement 11 according to FIG. 3 is constructed analogously to the measuring arrangement according to FIG. 1 in the areas III and IV. These areas are therefore not explained in detail here.
  • the actuator in region I follows the principle of the mass flow sensor already mentioned at the beginning, the structure being shown only schematically.
  • the vibratory System consists not as shown in Figure 1 from a diaphragm 15, but from a tube 27 which is flowed through in a manner not further dargestell ⁇ ter by a fluid.
  • This tube 27 can be vibrated, wherein schematically the elastic suspension 16 is shown, which is also equipped with a certain damping 28.
  • FIG. 4 shows an alternative construction of the measuring device
  • the resistance ⁇ R3 is at ground potential and has a resistance ⁇ value of 1 kü on.
  • the T configuration of the resistors causes the measurement arrangement in region III to settle faster in the reaction interval r after the enable signal has been set. Namely, a charge from the capacitance to be measured 17 are degraded during the reac tion interval ⁇ r has the impulse response there due to the import after passing through the switching edges 26 is still present.

Abstract

L'invention concerne un procédé de mesure de la variation dans le temps d'une capacité électrique et un dispositif de mesure servant à la mise en oeuvre de ce procédé. Pour mesurer la variation de la capacité (17), un courant de déplacement I(t) est détecté par un convertisseur courant-tension (19) et un signal de mesure M(t) est généré de manière correspondante. Selon l'invention, l'effet de la tension de commande électrique U(t) sur le résultat de mesure peut être supprimé lorsque la tension de commande comporte des composantes constantes et le convertisseur de courant-tension (19) est mis hors circuit pendant les flancs de commutation de la tension de commande. Ainsi, il est possible d'éliminer une réponse impulsionnelle à des variations de la tension d'alimentation U(t) agissant également sur le condensateur de mesure (17). Selon l'invention, une mesure plus précise peut ainsi être effectuée.
PCT/EP2011/064035 2010-08-23 2011-08-15 Procédé de mesure et dispositif de mesure pour acquérir une variation dans le temps d'une capacité électrique WO2012025417A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010035381A DE102010035381A1 (de) 2010-08-23 2010-08-23 Messverfahren und Messanordnung zur Erfassung der zeitlichen Veränderung einer elektrischen Kapazität
DE102010035381.7 2010-08-23

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WO2012025417A1 true WO2012025417A1 (fr) 2012-03-01

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PCT/EP2011/064035 WO2012025417A1 (fr) 2010-08-23 2011-08-15 Procédé de mesure et dispositif de mesure pour acquérir une variation dans le temps d'une capacité électrique

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WO (1) WO2012025417A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4365605A1 (fr) 2022-11-04 2024-05-08 Siemens Aktiengesellschaft Détermination d'un flux d'énergie électrique

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3812419A (en) 1973-03-05 1974-05-21 Us Army Electronic field mill
US20070065169A1 (en) * 2005-08-16 2007-03-22 Canon Kabushiki Kaisha Electric potential measuring apparatus electrostatic capacitance measuring apparatus, electric potential measuring method, electrostatic capacitance measuring method, and image forming apparatus
DE102006029443B3 (de) 2006-06-21 2008-01-31 Siemens Ag Sensor in mikromechanischer Bauweise zum Messen des Massendurchflusses nach dem Coriolis-Prinzip
US20090064781A1 (en) 2007-07-13 2009-03-12 Farrokh Ayazi Readout method and electronic bandwidth control for a silicon in-plane tuning fork gyroscope
DE102008052477A1 (de) 2008-10-20 2010-06-10 Siemens Aktiengesellschaft Als mikromechanisches System ausgebildeter Sensor für elektrische Felder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3812419A (en) 1973-03-05 1974-05-21 Us Army Electronic field mill
US20070065169A1 (en) * 2005-08-16 2007-03-22 Canon Kabushiki Kaisha Electric potential measuring apparatus electrostatic capacitance measuring apparatus, electric potential measuring method, electrostatic capacitance measuring method, and image forming apparatus
DE102006029443B3 (de) 2006-06-21 2008-01-31 Siemens Ag Sensor in mikromechanischer Bauweise zum Messen des Massendurchflusses nach dem Coriolis-Prinzip
US20090064781A1 (en) 2007-07-13 2009-03-12 Farrokh Ayazi Readout method and electronic bandwidth control for a silicon in-plane tuning fork gyroscope
DE102008052477A1 (de) 2008-10-20 2010-06-10 Siemens Aktiengesellschaft Als mikromechanisches System ausgebildeter Sensor für elektrische Felder

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
B. BAHREYNI ET AL.: "Analysis and Design of a Micromachined Electric-Field Sensor", JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, vol. 17, 2008, pages 31 - 36, XP011200970, DOI: doi:10.1109/JMEMS.2007.911870
JIRI DOSTAL: "Operationsverstärker", vol. 2, 1 January 1989, DR. ALFRED HÜTHIG VERLAG, Heidelberg, ISBN: 3-7785-1787-2, pages: 357 - 360, XP002666333 *

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