DE3634245A1 - Evaluating electronics for differential resistances to be used in sensors - Google Patents

Evaluating electronics for differential resistances to be used in sensors

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Publication number
DE3634245A1
DE3634245A1 DE19863634245 DE3634245A DE3634245A1 DE 3634245 A1 DE3634245 A1 DE 3634245A1 DE 19863634245 DE19863634245 DE 19863634245 DE 3634245 A DE3634245 A DE 3634245A DE 3634245 A1 DE3634245 A1 DE 3634245A1
Authority
DE
Germany
Prior art keywords
voltage
capacitor
comparator
output
ref
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Withdrawn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
DE19863634245
Other languages
German (de)
Inventor
Ruediger Prof Dr Ing Haberland
Bertold Vogt
Manfred Jagiella
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.)
Individual
Original Assignee
Individual
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Publication date
Priority claimed from DE19853524530 external-priority patent/DE3524530A1/en
Application filed by Individual filed Critical Individual
Priority to DE19863634245 priority Critical patent/DE3634245A1/en
Publication of DE3634245A1 publication Critical patent/DE3634245A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/225—Measuring circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
    • 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

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Abstract

As already described in Patent P 3524530.1, the measurement value in the evaluating electronics for differential resistances with a pulse-width-modulated squarewave output voltage, in which a capacitor is alternately charged via in each case one of the two part-resistances of the pick-up up to a reference voltage and then is recharged up to a second reference voltage, is, after low-pass filtering, strictly proportional to the measurement quantity. Supplementary to Patent P 3524530.1, further illustrative embodiments are presented here which are distinguished by a simple construction.

Description

Die Erfindung betrifft eine Auswerteelektronik für Differen­ tialwiderstände mit einer pulsbreiten modulierten Rechteck­ ausgangsspannung, bei der ein Kondensator wechselweise über jeweils einen der 2 Teilwiderstände auf die positive +U ref bzw. negative Referenzspannung -U ref umgeladen wird.The invention relates to evaluation electronics for differential resistors with a pulse-width modulated square-wave output voltage, in which a capacitor is alternately charged to the positive + U ref or negative reference voltage - U ref via one of the 2 partial resistors.

Wie bereits im Patent P 35 24 530. 1 beschrieben, weist das Umladeverfahren für die Auswertung von Differentialwiderstands­ aufnehmer aufgrund der geringen Bauelementeanzahl, Driftarmut und der Proportionalität der Ausgangsspannung zur Meßgröße wesent­ liche Vorteile gegenüber anderen Schaltungen auf.As already described in patent P 35 24 530.1, this shows Reloading procedure for the evaluation of differential resistance transducers due to the small number of components, low drift and the proportionality of the output voltage to the measurand is essential advantages over other circuits.

Bei einer nach dem bisherigen Stand der Technik verwendeten Schaltung (Fig. 1) werden die über den Teilwiderständen R 1 und R 2 abfallende Spannungen U 1 und U 2 gleichzeitig einem Additions- und Subtraktionswerk zugeführt. Am Ausgang des nachfolgenden Dividierers ist ein zur Meßgröße proportionaler Meßwert vorhanden. Bei der beschriebenen Meßwertverarbeitung werden eine Reihe von mathematischen Verknüpfungen auf elek­ tronischem Wege durchgeführt, bei denen die Stabilität der Bauelemente, vor allem des Dividierers, stark temperatur- und zeitabhängig sind.In one used in the prior art circuit (Fig. 1) 2 are simultaneously supplied to the voltage drop across the partial resistors R 1 and R 2 voltages U 1 and U an addition and Subtraktionswerk. A measured value proportional to the measured variable is present at the output of the subsequent divider. In the measured value processing described, a series of mathematical links are carried out electronically, in which the stability of the components, especially the divider, are strongly temperature and time-dependent.

Die Aufgabe einer Meßwertverarbeitung bei einem Differential­ widerstand wird erfindungsgemäß dadurch gelöst, daß ein Kon­ densator wechselweise über jeweils einen der beiden Teilwider­ stände umgeladen wird.The task of processing measured values for a differential Resistance is solved according to the invention in that a con capacitor alternately over one of the two parts stands is reloaded.

Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin, daß mit Hilfe dieser einfachen Auswerteelektronik ein zur Meßgröße proportionaler Meßwert nach der Tiefpaßfilterung aus dem pulsbreiten modulierten Rechtecksignal gewonnen wird, wobei der Meßwert von der Stabilität des zu ladenden Kondensators unabhängig ist.The advantages achieved with the invention are in particular in the fact that with the help of this simple evaluation electronics Measured value proportional to the measured variable after low-pass filtering is obtained from the pulse-width modulated square-wave signal, the measured value of the stability of the capacitor to be charged is independent.

Einige zusätzliche Ausführungsbeispiele der Erfindung sind in Fig. 2 bis 4 dargestellt.Some additional exemplary embodiments of the invention are shown in FIGS. 2 to 4.

In Fig. 2 ist eine Schaltung dargestellt, bei der der Kon­ densator 8 über die Schalter 7 und 12 (ähnlich einer "H-Schal­ tung") umgeladen wird. In der gezeigten Schaltung fließt der Ladestrom über den Widerstand 1 und den Schalter 7 und lädt damit den Kondensator 8 auf. Über den Schalter 12 ist die Gegenelektrode des Kondensators mit dem Referenzpunkt A (hier Masse) verbunden. Nachdem die Vergleichsspannung +U ref er­ reicht wurde, werden die Schalter 7 und 12 umgelegt, so daß nun Punkt B das gleiche Potential wie Punkt A besitzt (hier Masse). Hierdurch verschiebt sich an beiden Elektroden des Kondensators 8 die Spannung um den Betrag +U ref , so daß an Punkt C die Spannung -U ref anliegt. Durch den Umschaltvorgang wird der Kondensator am Punkt C von -U ref auf +U ref mit dem Ladestrom über den Widerstand 2 geladen. Die Komparatoren können hierbei so angeschlossen werden, daß entweder mit einem Komparator und einem Umschalter die Kondensatorspan­ nungen der Punkte B und C wechselweise mit der Vergleichs­ spannung +U ref verglichen werden, oder daß an jedem der Punkte B und C ein Komparator die Spannungen vergleicht.In Fig. 2, a circuit is shown in which the capacitor Kon 8 via the switches 7 and 12 (similar to an "H-scarf device") is reloaded. In the circuit shown, the charging current flows through the resistor 1 and the switch 7 and thus charges the capacitor 8 . The counter electrode of the capacitor is connected to reference point A (here ground) via switch 12 . After the reference voltage + U ref he was enough, the switches 7 and 12 are flipped so that point B now has the same potential as point A (here ground). This shifts the voltage on both electrodes of the capacitor 8 by the amount + U ref , so that the voltage - U ref is present at point C. The switchover process charges the capacitor at point C from - U ref to + U ref with the charging current via resistor 2 . The comparators can be connected so that either with a comparator and a switch, the capacitor voltages of points B and C are alternately compared with the comparison voltage + U ref , or that at each of points B and C a comparator compares the voltages.

In Fig. 3 ist eine Schaltung dargestellt, bei der der Span­ nungsteiler bestehend aus den Widerständen 3 und 4 direkt mit dem Ausgang des Komparators verbunden ist. Hierbei wird eine Schalthysterese dadurch erzeugt, daß man den Komparator über den Spannungsteiler mitkoppelt. Die Ausgangsspannung des Kom­ parators bleibt, solange der Kondensator 8 die positive bzw. negative Referenzspannung noch nicht erreicht hat, auf kon­ stantem Niveau (Aussteuerspannung).In Fig. 3 a circuit is shown in which the voltage divider consisting of the resistors 3 and 4 is connected directly to the output of the comparator. Here, a switching hysteresis is generated by coupling the comparator via the voltage divider. The output voltage of the comparator remains as long as the capacitor 8 has not yet reached the positive or negative reference voltage, at a constant level (control voltage).

Wird der Komparator mit symmetrischer Versorgungsspannung betrieben, so läßt sich das pulsbreiten modulierte Rechteck­ ausgangssignal direkt am Ausgang des Komparators abnehmen, wobei zusätzlich die Amplitude mittels Referenzspannungs­ dioden stabilisiert werden kann. If the comparator with symmetrical supply voltage operated, so the pulse width modulated rectangle take the output signal directly at the output of the comparator, the amplitude using reference voltage diodes can be stabilized.  

In Fig. 4 ist eine Schaltung dargestellt, bei der die Lade­ spannung U 1 bzw. -U 1 direkt am Ausgang des Komparators 9 abgegriffen wird, wobei der Strom entweder mittels eines Schalters oder wie in Fig. 4 zu sehen, durch 2 Dioden auf die Teilwiderstände 1 und 2 verzweigt wird.In Fig. 4 a circuit is shown in which the charging voltage U 1 or - U 1 is tapped directly at the output of the comparator 9 , the current either by means of a switch or, as can be seen in Fig. 4, by 2 diodes the partial resistors 1 and 2 is branched.

Claims (4)

1. Auswerteelektronik für einen Differentialwiderstand mit wechselseitigem Umladevorgang (über RC-Glied) und pulsbreiten modulierten Rechteckausgangsspannung ist, dadurch gekennzeich­ net, daß bei Differentialwiderständen mit gemeinsamer Span­ nungsversorgung der wechselseitige Umladevorgang, durch Umschalten der Stromrichtung am Kondensator (H-Schaltung) mittels zweier Umschalter erreicht wird (Fig. 1).1. Evaluation electronics for a differential resistor with mutual recharging process (via RC element) and pulse-width modulated square-wave output voltage, characterized in that with differential resistors with a common voltage supply, the mutual recharging process, by switching the current direction on the capacitor (H circuit) by means of two switches is reached ( Fig. 1). Weiterhin ist hierbei nur eine Vergleichsspannung U ref nötig, da das Bezugspotential (Masse) am Kondensator synchron zum Ladevorgang umgeschaltet wird.Furthermore, only a comparison voltage U ref is necessary here, since the reference potential (ground) on the capacitor is switched synchronously with the charging process. 2. Auswerteelektronik nach Anspruch 1, dadurch gekennzeichnet, daß der Spannungsteiler zur Erzeugung der Referenzspannung U ref , direkt mit dem Ausgang des Komparators verbunden ist (Kompara­ tor mit Hysterese), wobei die Amplitude der pulsbreiten modu­ lierten Rechteckausgangsspannung mittels Referenzspannungs­ dioden stabilisiert wird.2. Evaluation electronics according to claim 1, characterized in that the voltage divider for generating the reference voltage U ref , is directly connected to the output of the comparator (comparator with hysteresis), the amplitude of the pulse-width modulated rectangular output voltage being stabilized by means of reference voltage diodes. 3. Auswerteelektronik nach Anspruch 1 und 2, dadurch gekenn­ zeichnet, daß die Ladespannung U 1 bzw. -U 1 direkt am Ausgang des Komparators abgenommen wird.3. Evaluation electronics according to claim 1 and 2, characterized in that the charging voltage U 1 or - U 1 is taken off directly at the output of the comparator.
DE19863634245 1985-07-10 1986-10-08 Evaluating electronics for differential resistances to be used in sensors Withdrawn DE3634245A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19863634245 DE3634245A1 (en) 1985-07-10 1986-10-08 Evaluating electronics for differential resistances to be used in sensors

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19853524530 DE3524530A1 (en) 1985-07-10 1985-07-10 Evaluating electronics for differential resistors to be used in sensors
DE19863634245 DE3634245A1 (en) 1985-07-10 1986-10-08 Evaluating electronics for differential resistances to be used in sensors

Publications (1)

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DE3634245A1 true DE3634245A1 (en) 1988-04-21

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3912032C1 (en) * 1989-04-12 1990-09-13 Messerschmitt-Boelkow-Blohm Gmbh, 8012 Ottobrunn, De
EP0427882A1 (en) * 1989-11-14 1991-05-22 Robert Bosch Gmbh Apparatus for measuring small displacements
DE4016316A1 (en) * 1990-05-21 1991-11-28 Bosch Gmbh Robert EVALUATION FOR THE SIGNALS OF A SIGNAL SOURCE
DE4103200A1 (en) * 1991-02-02 1992-08-06 Vdo Schindling Measurement transducer for physical parameters - has two sensors e.g. capacitive, inductive or resistor sensors, and changeover switch selecting on sensor at time for connection to evaluation circuit

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3912032C1 (en) * 1989-04-12 1990-09-13 Messerschmitt-Boelkow-Blohm Gmbh, 8012 Ottobrunn, De
EP0427882A1 (en) * 1989-11-14 1991-05-22 Robert Bosch Gmbh Apparatus for measuring small displacements
DE4016316A1 (en) * 1990-05-21 1991-11-28 Bosch Gmbh Robert EVALUATION FOR THE SIGNALS OF A SIGNAL SOURCE
DE4016316B4 (en) * 1990-05-21 2004-02-12 Robert Bosch Gmbh Evaluation circuit for the signals of a signal source
DE4103200A1 (en) * 1991-02-02 1992-08-06 Vdo Schindling Measurement transducer for physical parameters - has two sensors e.g. capacitive, inductive or resistor sensors, and changeover switch selecting on sensor at time for connection to evaluation circuit

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