DE3925579A1 - Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit - Google Patents

Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit

Info

Publication number
DE3925579A1
DE3925579A1 DE19893925579 DE3925579A DE3925579A1 DE 3925579 A1 DE3925579 A1 DE 3925579A1 DE 19893925579 DE19893925579 DE 19893925579 DE 3925579 A DE3925579 A DE 3925579A DE 3925579 A1 DE3925579 A1 DE 3925579A1
Authority
DE
Germany
Prior art keywords
partial
circuit
capacitor
sample
differential capacitor
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Withdrawn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
DE19893925579
Other languages
German (de)
Inventor
Joachim Hannappel
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.)
Mannesmann VDO AG
Original Assignee
Mannesmann VDO AG
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 Mannesmann VDO AG filed Critical Mannesmann VDO AG
Priority to DE19893925579 priority Critical patent/DE3925579A1/en
Publication of DE3925579A1 publication Critical patent/DE3925579A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
    • G01P15/02—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses
    • G01P15/08—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values
    • G01P15/125—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration by making use of inertia forces using solid seismic masses with conversion into electric or magnetic values by capacitive pick-up
    • 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
    • G01D5/241—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 by relative movement of capacitor electrodes
    • G01D5/2417—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 by relative movement of capacitor electrodes by varying separation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/14—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
    • G01L1/142—Measuring force or stress, in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/12—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor
    • G01L9/125—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor with temperature compensating means

Abstract

A circuit for a differential capacitor enables the first of two partial capacitances (C1, C2) to be charged to a defined voltage via a first controlled switch (S1). A second controlled switch (S2) enables the two capacitances to be connected in parallel. The second capacitance (C2) is discharged via a third controlled switch (S3) and connected to the input of a sample-and-hold circuit (1). USE/ADVANTAGE - For use with a differential capacitor consisting of two partial capacitances. Sensing acceleration, force, pressure, or distance. Enables changes in differential capacitance corresp. to input parameter to be converted into electrical signal substantially without error influences.

Description

Die Erfindung betrifft eine Schaltungsanordnung für einen Differentialkondensator, der aus einem ersten und einem zweiten Teilkondensator besteht, deren Kapazitäten gegenläufig von einer Eingangsgröße abhängig sind, und ein Verfahren zum Betrieb dieser Schaltungsanordnung.The invention relates to a circuit arrangement for a Differential capacitor consisting of a first and a second partial capacitor, whose capacities in the opposite direction depend on an input variable, and a Method for operating this circuit arrangement.

Bei verschiedenen Sensoren zur Erzeugung eines elektrischen Signals in Abhängigkeit von einer Eingangsgröße sind Differentialkondensatoren vorgesehen, bei welchen die Kapazitäten zweier Teilkondensatoren gegenläufig von der Eingangsgröße abhängig sind. Dieses Prinzip wird beispielsweise bei Beschleunigungs-, Druck-, Weg- und Kraftsensoren angewendet. Durch Messung und anschließende Differenzbildung der Kapazitätswerte kann in einer Auswerteschaltung ein elektrisches Signal gewonnen werden, das die Eingangsgröße darstellt. In diese Auswertung gehen jedoch verschiedene unerwünschte Größen ein - wie beispielsweise die Temperaturabhängigkeit der Kapazitäten der Teilkondensatoren.With various sensors for generating an electrical Signals are dependent on an input variable Differential capacitors are provided, in which the Capacities of two partial capacitors in opposite directions from the Input size are dependent. This principle will for example in acceleration, pressure, displacement and Force sensors applied. By measurement and subsequent Difference formation of the capacitance values can in one Evaluation circuit an electrical signal can be obtained that represents the input quantity. Go into this evaluation however, various undesirable sizes - such as for example the temperature dependence of the capacities  of the partial capacitors.

Aufgabe der vorliegenden Erfindung ist es, eine möglichst einfache Schaltungsanordnung anzugeben, bei welcher die der Eingangsgröße entsprechende Änderung des Differentialkondensators weitgehend ohne Störeinflüsse in ein elektrisches Signal umgewandelt wird.The object of the present invention is, if possible specify simple circuit arrangement in which the Input variable corresponding change of Differential capacitor largely without interference in an electrical signal is converted.

Die erfindungsgemäße Schaltungsanordnung ist dadurch gekennzeichnet, daß der erste Teilkondensator über einen ersten steuerbaren Schalter auf eine vorgegebene Spannung aufladbar ist, daß ein zweiter steuerbarer Schalter zur Parallelschaltung beider Teilkondensatoren vorgesehen ist und daß der zweite Teilkondensator mit einem dritten steuerbaren Schalter entladbar und mit dem Eingang einer Abtast- und Halteschaltung verbunden ist.The circuit arrangement according to the invention is thereby characterized in that the first partial capacitor via a first controllable switch to a predetermined voltage is chargeable that a second controllable switch for Parallel connection of both partial capacitors is provided and that the second partial capacitor with a third controllable switch unloadable and with the input of a Sample and hold circuit is connected.

Die Erfindung umfaßt ferner vorteilhafte Verfahren zum Betrieb der erfindungsgemäßen Schaltungsanordnung, die im einzelnen in den Unteransprüchen angegeben sind.The invention also includes advantageous methods for Operation of the circuit arrangement according to the invention individual are specified in the subclaims.

Die Erfindung läßt zahlreiche Ausführungsformen zu. Eine davon ist schematisch in der Zeichnung anhand mehrerer Figuren dargestellt und nachfolgend beschrieben. Es zeigt:The invention allows numerous embodiments. A of which is schematic in the drawing based on several Figures shown and described below. It shows:

Fig. 1 eine erfindungsgemäße Schaltungsanordnung und Fig. 1 shows a circuit arrangement according to the invention and

Fig. 2 eine schematische Darstellung eines Differentialkondensators. Fig. 2 is a schematic representation of a differential capacitor.

Gleiche Teile sind in den Figuren mit gleichen Bezugszeichen versehen.Identical parts are given the same reference symbols in the figures Mistake.

Bei der Schaltungsanordnung nach Fig. 1 sind die Teilkondensatoren C1 und C2 im Sinne eines Ersatzbildes als zwei veränderbare Kondensatoren dargestellt, von denen jeweils eine Platte mit Massepotential verbunden ist. Der erste Teilkondensator C1 kann über einen ersten steuerbaren Schalter S1 mit einer Betriebsspannung beaufschlagt werden. Ein weiterer steuerbarer Schalter S2 dient zur Verbindung beider Teilkondensatoren, während ein dritter steuerbarer Schalter den zweiten Teilkondensator C2 kurzschließen und somit entladen kann. Der zweite Teilkondensator ist ferner mit dem Eingang einer Abtast- und Halteschaltung 1 verbunden, an deren Ausgang 2 die gewünschte Spannung U abnehmbar ist. Außer dem Anschluß 3 für die Betriebsspannung Ub weist die Schaltungsanordnung nach Fig. 1 noch einen Anschluß 4 für Massepotential auf.In the circuit arrangement according to FIG. 1, the partial capacitors C 1 and C 2 are shown as two changeable capacitors in the sense of an equivalent image, one of which is connected to ground potential. The first partial capacitor C 1 can be supplied with an operating voltage via a first controllable switch S 1 . Another controllable switch S 2 is used to connect the two partial capacitors, while a third controllable switch can short-circuit and thus discharge the second partial capacitor C 2 . The second partial capacitor is also connected to the input of a sample and hold circuit 1 , at the output 2 of which the desired voltage U can be removed. In addition to the connection 3 for the operating voltage Ub, the circuit arrangement according to FIG. 1 also has a connection 4 for ground potential.

Für die steuerbaren Schalter S1 bis S3 ist ferner eine Steuerschaltung 5 vorgesehen, welche Rechtecksignale erzeugt, die abwechselnd etwa gleichzeitig die Schalter S1 und S3 und danach den Schalter S2 schließen. Dementsprechend wird in einer ersten Phase der Teilkondensator C1 auf die Betriebsspannung Ub aufgeladen und der Teilkondensator C2 entladen. Nach dem Öffnen der Schalter S1 und S3 wird in einer zweiten Phase, in der der Schalter S2 geschlossen ist, die Ladung des Teilkondensators C1 auf beide Teilkondensatoren verteilt. Am Ende dieser zweiten Phase wird die Spannung am Teilkondensator C2 abgetastet und bis zum nächsten Abtastvorgang in der Abtast- und Halteschaltung 1 gespeichert. Die Abtast- und Halteschaltung 1 hat einen niederohmigen Ausgang, so daß die Spannung U in einfacher Weise weitergeleitet werden kann.A control circuit 5 is also provided for the controllable switches S 1 to S 3 , which generates square-wave signals which alternately close the switches S 1 and S 3 and then the switch S 2 approximately simultaneously. Accordingly, in a first phase, the partial capacitor C 1 is charged to the operating voltage Ub and the partial capacitor C 2 is discharged. After opening the switches S 1 and S 3 , the charge of the partial capacitor C 1 is distributed to both partial capacitors in a second phase, in which the switch S 2 is closed. At the end of this second phase, the voltage at the partial capacitor C 2 is sampled and stored in the sample and hold circuit 1 until the next sampling operation. The sample and hold circuit 1 has a low-resistance output, so that the voltage U can be passed on in a simple manner.

Zur weiteren Verdeutlichung der Erfindung werden im folgenden Gleichungen abgeleitet, die das Verhalten der erfindungsgemäßen Schaltungsanordnung bestimmen.To further clarify the invention in derived the following equations that determine the behavior of the Determine circuit arrangement according to the invention.

Die Spannung an zwei parallelgeschalteten Kondensatoren ergibt sich nach dem Umladevorgang zu: The voltage across two capacitors connected in parallel after the reloading process results in:  

U = Ub * [C1/(C1 + C2)]U = Ub * [C 1 / (C 1 + C 2 )]

Dabei ist Ub diejenige Spannung, auf welche der Kondensator C1 vor dem Zusammenschalten aufgeladen war.Ub is the voltage to which the capacitor C 1 was charged prior to interconnection.

Zur Erläuterung des Verhaltens der Kapazitäten der Teilkondensatoren C1 und C2 wird auf die schematische Darstellung des Differentialkondensators in Fig. 2 hingewiesen. Dabei wird von drei parallelen Kondensatorplatten 7, 8, 9 ausgegangen, wobei die mittlere Platte in Abhängigkeit von einer Eingangsgröße in Richtung des Doppelpfeils verschiebbar ist. Während in einer mittleren Stellung der Platte 8 die Abstände jeweils d betragen, werden die Abstände bei einer Verschiebung der Platte 8 (d+δ) bzw. (d-δ). Die Werte der Teilkapazitäten C1 und C2 ergeben sich dann zu:To explain the behavior of the capacitances of the partial capacitors C 1 and C 2 , reference is made to the schematic illustration of the differential capacitor in FIG. 2. Three parallel capacitor plates 7 , 8 , 9 are assumed, the middle plate being displaceable in the direction of the double arrow depending on an input variable. While in a central position of the plate 8 the distances are d, the distances become (d + δ) or (d-δ) when the plate 8 is displaced. The values of the partial capacities C 1 and C 2 then result in:

C1 = ε * A/(d + δ)C 1 = ε * A / (d + δ)

C2 = ε * A/(d - δ)C 2 = ε * A / (d - δ)

Somit ist dargelegt, daß die Spannung lediglich vomIt is thus shown that the voltage is only from

C1 + C2 = ε * A/(d + δ) + ε * A/(d - δ)C 1 + C 2 = ε * A / (d + δ) + ε * A / (d - δ)

= 2 * ε * A d/(d² - δ²)= 2 * ε * A d / (d² - δ²)

In Gleichung (1) eingesetzt ergibt sich dann:When used in equation (1), the following results:

U = Ub * {ε * A/(d + δ)/[2 * ε * A * d/(d² - δ²)]}U = Ub * {ε * A / (d + δ) / [2 * ε * A * d / (d² - δ²)]}

= Ub * 1/2 = (d - δ)/d= Ub * 1/2 = (d - δ) / d

= Ub * 1/2 * (1 - δ/d)= Ub * 1/2 * (1 - δ / d)

Somit ist dargelegt, daß die Spannung lediglich vom Verhältnis δ zu d abhängt und unabhängig von anderen Größen, wie beispielsweise ε ist. Somit gehen die Temperaturfehler nicht in die Spannung U ein.It is thus shown that the voltage is only from Ratio δ to d depends and is independent of other quantities, such as ε. So the temperature errors go not in the voltage U.

Claims (3)

1. Schaltungsanordnung für einen Differentialkondensator, der aus einem ersten und einem zweiten Teilkondensator besteht, deren Kapazitäten gegenläufig von einer Eingangsgröße abhängig sind, dadurch gekennzeichnet, daß der erste Teilkondensator (C1) über einen ersten steuerbaren Schalter (S1) auf eine vorgegebene Spannung aufladbar ist, daß ein zweiter steuerbarer Schalter (S2) zur Parallelschaltung beider Teilkondensatoren (C1, C2) vorgesehen ist und daß der zweite Teilkondensator (C2) mit einem dritten steuerbaren Schalter (S3) entladbar und mit dem Eingang einer Abtast- und Halteschaltung (1) verbunden ist.1. Circuit arrangement for a differential capacitor, which consists of a first and a second partial capacitor, the capacitances of which are dependent on an input variable, characterized in that the first partial capacitor (C 1 ) via a first controllable switch (S 1 ) to a predetermined voltage is chargeable that a second controllable switch (S 2 ) is provided for the parallel connection of both partial capacitors (C 1 , C 2 ) and that the second partial capacitor (C 2 ) can be discharged with a third controllable switch (S 3 ) and with the input of a scan - And hold circuit ( 1 ) is connected. 2. Verfahren zum Betrieb der Schaltungsanordnung nach Anspruch 1, dadurch gekennzeichnet, daß in einer ersten Phase der erste Teilkondensator aufgeladen wird, daß in einer zweiten Phase die Teilkondensatoren durch Schließen des zweiten Schalters parallelgeschaltet werden, daß am Ende der zweiten Phase die Spannung an den Teilkondensatoren abgetastet wird und daß in einer dritten Phase der zweite Teilkondensator entladen wird.2. Method for operating the circuit arrangement according to Claim 1, characterized in that in a first Phase of the first partial capacitor is charged that in a second phase by closing the partial capacitors of the second switch are connected in parallel, that at the end the second phase, the voltage across the partial capacitors is scanned and that in a third phase the second  Partial capacitor is discharged. 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß die erste und die dritte Phase sich mindestens teilweise überlappen.3. The method according to claim 2, characterized in that the first and third phases differ at least partially overlap.
DE19893925579 1989-08-02 1989-08-02 Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit Withdrawn DE3925579A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19893925579 DE3925579A1 (en) 1989-08-02 1989-08-02 Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19893925579 DE3925579A1 (en) 1989-08-02 1989-08-02 Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit

Publications (1)

Publication Number Publication Date
DE3925579A1 true DE3925579A1 (en) 1991-02-07

Family

ID=6386361

Family Applications (1)

Application Number Title Priority Date Filing Date
DE19893925579 Withdrawn DE3925579A1 (en) 1989-08-02 1989-08-02 Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit

Country Status (1)

Country Link
DE (1) DE3925579A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4131093A1 (en) * 1991-09-18 1993-04-08 Mess Top Engineering Ges Fuer Deriving electrical measurement signal proportional to physical measurement parameter, e.g. relative displacement - stimulating transducer with variable impedance dependent on measurement parameter using clocked stimulation voltage, and forming signal from sampled transducer output signal
WO1993024818A2 (en) * 1992-05-28 1993-12-09 Rosemount Inc. Correction for a pressure transducer

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4131093A1 (en) * 1991-09-18 1993-04-08 Mess Top Engineering Ges Fuer Deriving electrical measurement signal proportional to physical measurement parameter, e.g. relative displacement - stimulating transducer with variable impedance dependent on measurement parameter using clocked stimulation voltage, and forming signal from sampled transducer output signal
WO1993024818A2 (en) * 1992-05-28 1993-12-09 Rosemount Inc. Correction for a pressure transducer
WO1993024818A3 (en) * 1992-05-28 1994-02-03 Rosemount Inc Correction for a pressure transducer

Similar Documents

Publication Publication Date Title
DE2842028C3 (en) Device for measuring the capacitance of a capacitor
DE19644125C2 (en) Capacitive sensor interface circuit
DE19739532C2 (en) Capacitance sensor interface circuit
EP0583250B1 (en) Integratable conductivity measuring device
DE10247467A1 (en) Capacitive sensor for detecting a physical quantity, which detects a physical quantity along a plurality of axes
DE2221741A1 (en) Device for capacitive measurement of the local position of separating layers between two adjacent media
DE19851506C1 (en) Capacitive sensor evaluation method e.g. for pressure sensor, has periodic input signal supplied simultaneously to integration path containing reference capacitor and series circuit containing resistor and sensor capacitor
DE2950433A1 (en) ELECTRONIC CIRCUIT WITH SWITCHED CAPACITIES
DE4421906C2 (en) Method and circuit arrangement for measuring the resistance of a resistance sensor
DE102004012862A1 (en) Device for detecting a physical quantity
EP0847138A2 (en) Capacitive sensing device
DE3925579A1 (en) Circuit for differential capacitor contg. two partial capacitances - contains three controlled switches and sample-and-hold circuit
EP0628155B1 (en) Circuit for a transducer
DE19753682C2 (en) Interface circuit for a capacitive sensor
DE19708330C1 (en) Evaluation method for capacitive sensor esp pressure sensor
DE4423907C2 (en) Capacitive sensor
DE2460079C3 (en) Method for determining the position of the wiper of a potentiometer and circuit arrangement for carrying out the method
DE102019129802A1 (en) Capacitive sensor device, method for operating a capacitive sensor device, operating device and vehicle
DE4340481C1 (en) Capacitive sensor
DE3708770C2 (en)
DE3115195C2 (en)
DE2752560C3 (en) Process for analog-digital conversion of voltages according to the multiple integration principle and circuit arrangement for carrying out the process
DE2547746B2 (en) Device for forming the arithmetic mean value of a measured variable
DE2045813C3 (en) Dielectric measuring device
DE3738815C1 (en) Input circuit for a data acquisition device

Legal Events

Date Code Title Description
8139 Disposal/non-payment of the annual fee