WO1992000504A1 - Device for reliably detecting faults and suppressing noise peaks in potentiometer assessment - Google Patents

Device for reliably detecting faults and suppressing noise peaks in potentiometer assessment Download PDF

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Publication number
WO1992000504A1
WO1992000504A1 PCT/DE1991/000473 DE9100473W WO9200504A1 WO 1992000504 A1 WO1992000504 A1 WO 1992000504A1 DE 9100473 W DE9100473 W DE 9100473W WO 9200504 A1 WO9200504 A1 WO 9200504A1
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WO
WIPO (PCT)
Prior art keywords
potentiometer
resistor
filter
analog
digital converter
Prior art date
Application number
PCT/DE1991/000473
Other languages
German (de)
French (fr)
Inventor
Helmut Denz
Original Assignee
Robert Bosch Gmbh
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 Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO1992000504A1 publication Critical patent/WO1992000504A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D11/00—Arrangements for, or adaptations to, non-automatic engine control initiation means, e.g. operator initiated
    • F02D11/06—Arrangements for, or adaptations to, non-automatic engine control initiation means, e.g. operator initiated characterised by non-mechanical control linkages, e.g. fluid control linkages or by control linkages with power drive or assistance
    • F02D11/10—Arrangements for, or adaptations to, non-automatic engine control initiation means, e.g. operator initiated characterised by non-mechanical control linkages, e.g. fluid control linkages or by control linkages with power drive or assistance of the electric type
    • F02D11/107—Safety-related aspects
    • 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
    • G01D5/16—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 resistance
    • G01D5/165—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 resistance by relative movement of a point of contact or actuation and a resistive track
    • 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
    • G01R27/16—Measuring impedance of element or network through which a current is passing from another source, e.g. cable, power line
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/54—Testing for continuity

Definitions

  • the invention relates to a device for safe execution and noise peak suppression in a potentiometer evaluation, in particular in a throttle valve potentiometer in an internal combustion engine.
  • the throttle valve potentiometer represents a mechanically changeable resistor, from whose slider the signal voltage is tapped.
  • the tapped signal voltage should lie within narrow tolerances and the wiper currents should be as small as possible ( ⁇ 20 .uA) for the best noise suppression. Fault detection for short circuits and cable drop at the potentiometer connections is also required.
  • a monitoring device for the throttle valve potentiometer is known from DE-OS 37 14 697. The throttle valve potentiometer, the wiper position of which is in a predetermined relationship to the position of the accelerator pedal, is connected on the one hand to the operating voltage via a measuring resistor and on the other hand to ground.
  • the invention has for its object to provide a device with which, when evaluating output signals of a potentiometer arrangement, on the one hand a failure of the potentiometer or a cable break at the wiper connection of the potentiometer is recognized and on the other hand the effect of noise peaks on the output signal of the potentiometer arrangement errors can be suppressed as best as possible.
  • the device according to the invention has the advantage that a missing output signal of the potentiometer, or. A cable break at the grinder connection of the potentiometer is reliably detected in normal operation despite the low potentiometer current.
  • Noise peaks which can occur when the potentiometer path is abraded, can be better suppressed or prevented by an appropriate choice of a filter from having an effect on the analog-digital converter.
  • FIG. 1 shows a basic illustration of a conventional evaluation circuit for a ratiometrically evaluated throttle valve potentiometer
  • FIG. 2 shows a device according to the invention for reliable failure detection and noise peak suppression for a throttle valve potentiometer
  • a throttle valve potentiometer 10 is located in the throttle valve generator DKG between the buffered positive supply voltage U, which is 5 volts, and ground switched.
  • the grinder S of the throttle valve potentiometer 10 there is possibly a short-term noise resistance, which is shown as resistor 11.
  • a protective resistor 18, the value of which is approximately 800 ohms, is connected downstream of the wiper S, the other connection of the protective resistor 18 leading to the output A of the throttle valve generator DKG and connected to a corresponding connection of the control unit SG is.
  • control unit SG The relevant connection of the control unit SG is connected via a filter resistor 12 to an analog-digital converter 13 which is also between the supply voltage and ground. Between the input of the analog-digital converter 13 and ground is a filter capacitor 14, at the input of the control unit SG there is a pull-down resistor 15 which is connected to ground and is used for potential definition in the event of a cable drop.
  • a protective circuit which consists of the Zener diodes 23 and 24, is arranged at the input of the analog-digital converter 13 in such a way that it protects it from excessive positive or negative voltage peaks.
  • the analog-to-digital converter 13 is represented in FIG. 1 by an equivalent circuit which is formed from a resistor 16 and a voltage of 2.5 volts connected to terminal 17.
  • the throttle valve potentiometer voltage U lies between the wiper S of the throttle valve potentiometer 10 and ground, the current I flows as the output signal of the throttle valve potentiometer via the wiper contact S.
  • the voltage U is at the pull-down resistor 15 and the voltage U at the filter capacitor 14. Depending on the voltage U flows into the analog-digital converter 13
  • the throttle valve potentiometer 10 lies between the buffered supply voltage U and ground.
  • the potentiometer voltage U changes depending on the position of the throttle valve.
  • the characteristic curve is usually designed in such a way that U reaches a maximum of 4.8 volts and a minimum of 0.2 volts, so that there is an implausible range for various types of faults in line shorts or interruptions.
  • a filter time constant TT 5 ms is implemented with a resistor 12 _ 12 KOh and a capacitor 14 with 440 Nannofarad.
  • the current I must be chosen to be as small as possible so that the voltage drop is kept as small as possible becomes relatively large.
  • the total resistance of the two resistors 12 and 15 must be less than 33 KOhm, with a value of 12 KOhm for the resistor 12, resistor 15 must be less than 21 KOhm. In normal operation, however, this results in a high wiper current I of 220 ⁇ A when the wiper track is tapped at the top, which leads to sharp voltage drops when the noise resistance 11 is increased.
  • FIG. 2 shows a circuit arrangement with which an improved noise peak suppression is possible while maintaining the failure detection during the potentiometer evaluation.
  • the throttle valve potentiometer 10 is connected to a buffered reference voltage U and to ground, as shown in FIG.
  • the higher voltage is generated via a series resistor 20, which is connected to a battery voltage terminal 21, and a Zener diode 22, which lies between the series resistor 20 and ground.
  • the pull-up resistor 19 can also be connected directly to the battery voltage, that is to say can be connected directly to the battery voltage terminal 21.
  • the input circuitry of the circuit arrangement according to FIG. 2, or the configuration of the throttle valve potentiometer transmitter DKG corresponds to the arrangement already known from FIG.
  • a calculation of the circuit arrangement according to FIG. 2 shows the advantages over the circuits according to FIG. 1.
  • the potential at the analog-digital converter input must be raised above a threshold of approximately 4.9 volts.
  • the total current from analog-digital converter 13 and protective circuit is: I - 3 uA.
  • FIGS. 1 and 2 can of course also be used for other potentiometer evaluations than for throttle valve potentiometer evaluations.
  • An airflow meter, which also contains a potentiometer, is given here as an example.

Abstract

The invention relates to a device for reliably detecting faults and suppressing noise peaks in potentiometer assessment in which the signal output of the potentiometer is connected to a voltage higher than the reference voltage via a pull-up resistor (19) so that when the signal line is interrupted there is, at the next analog-digital converter (13), a higher potential compared with that of smooth operation which is used to detect faults. If the circuit is suitably designed, the wiper current of the potentiometer is kept to a minimum and the effects of noise peaks or micro-interruptions are reduced.

Description

Einrichtung zur sicheren Ausfallerkennung und Rauschspitzenunter- drückuncr bei einer Potentiometerauswertunq Device for reliable failure detection and noise peak suppression during a potentiometer evaluation
Stand der TechnikState of the art
Die Erfindung betrifft eine Einrichtung zur sicheren Ausf llerken¬ nung und Rauschspitzenunterdrückung bei einer Potentiometerauswer¬ tung, insbesondere bei einem Drosselklappenpotentiometer bei einer Brennkraftmaschine.The invention relates to a device for safe execution and noise peak suppression in a potentiometer evaluation, in particular in a throttle valve potentiometer in an internal combustion engine.
Es ist allgemein bekannter Stand der Technik, die Drosselklappen¬ stellung, von der die Menge der vom Motor angesaugten Luft abhängig ist, mit Hilfe eines Drosselklappenpotentiometers zu bestimmen. Da¬ bei stellt das Drosselklappenpotentiometer einen mechanisch verän¬ derbaren Widerstand dar, an dessen Schleifer die SignalSpannung ab¬ gegriffen wird.It is generally known prior art to determine the throttle valve position, on which the amount of air drawn in by the engine depends, with the aid of a throttle valve potentiometer. The throttle valve potentiometer represents a mechanically changeable resistor, from whose slider the signal voltage is tapped.
Die abgegriffene SignalSpannung soll innerhalb enger Toleranzen lie¬ gen und die Schleiferströme sollen zwecks bester Rauschunterdrückung möglichst klein (< 20 .uA) sein. Ferner ist eine Fehlererkennung für Kurzschlüsse und Kabelabfall an den Potentiometeranschlüssen er¬ forderlich. Eine Uberwachungseinrichtung für das Drosselklappenpotentiometer ist aus der DE-OS 37 14 697 bekannt. Dabei wird das Drosselklappenpoten¬ tiometer, dessen Schleiferstellung in einer vorgegebenen Beziehung zur Stellung des Fahrpedals steht, einerseits über einen Meßwider- stand mit der Betriebsspannung und andererseits an Masse angeschlos¬ sen. Zur Erkennung von unerwünschten Nebenschlußwiderständen, die besonders im gealterten Zustand des Potentiometers auftreten können und zu einem erhöhten Strom durch das Potentiometer und den Meßwert¬ widerstand führen, wird der am Meßwiderstand auftretende Spannungs¬ abfall gemessen. Bei Abweichung von einem vorgegebenen Wert wird ein Nebenschlußwiderstand erkannt.The tapped signal voltage should lie within narrow tolerances and the wiper currents should be as small as possible (<20 .uA) for the best noise suppression. Fault detection for short circuits and cable drop at the potentiometer connections is also required. A monitoring device for the throttle valve potentiometer is known from DE-OS 37 14 697. The throttle valve potentiometer, the wiper position of which is in a predetermined relationship to the position of the accelerator pedal, is connected on the one hand to the operating voltage via a measuring resistor and on the other hand to ground. In order to detect undesired shunt resistances, which can occur particularly when the potentiometer is in an aged state and lead to an increased current through the potentiometer and the measured value resistor, the voltage drop occurring at the measuring resistor is measured. If there is a deviation from a specified value, a shunt resistance is detected.
Mit dieser Uberwachungseinrichtung für ein Drosselklappenpotentio¬ meter ist es jedoch nicht möglich, einen Ausfall des Potentiometers selbst oder einen Kabelbruch am Schleiferanschluß des Potentiometers zu erkennen. Außerdem können Rauschspitzen, die bei kurzfristigen WiderStandserhöhungen oder gar Unterbrechungen am Schleifer auftre¬ ten können, zu Störungen führen. Diese kurzzeitigen Widerstandser- höhungen treten insbesondere bei einem gealterten Potentiometer auf, bei dem durch Abrieb Kohlepartikel unter den Schleifer geraten.With this monitoring device for a throttle valve potentiometer, however, it is not possible to detect a failure of the potentiometer itself or a cable break at the wiper connection of the potentiometer. In addition, noise peaks, which can occur with short-term increases in resistance or even interruptions on the grinder, can lead to faults. These brief increases in resistance occur particularly in an aged potentiometer, in which carbon particles get under the grinder due to abrasion.
Der Erfindung liegt die Aufgabe zugrunde, eine Einrichtung zu schaf¬ fen, mit der bei der Auswertung von Ausgangssignalen einer Potentio- meteranordnung einerseits ein Ausfall des Potentiometers oder ein Kabelbruch am Schleiferanschluß des Potentiometers erkannt wird und andererseits die Auswirkung von Rauschspitzen am Ausgangssignal der Potentiometeranordnung die zu Fehlern führen kann, bestmöglichst unterdrückt werden. Vorteile der ErfindungThe invention has for its object to provide a device with which, when evaluating output signals of a potentiometer arrangement, on the one hand a failure of the potentiometer or a cable break at the wiper connection of the potentiometer is recognized and on the other hand the effect of noise peaks on the output signal of the potentiometer arrangement errors can be suppressed as best as possible. Advantages of the invention
Die erfindungsgemäße Einrichtung hat den Vorteil, daß ein fehlendes AusgangsSignals des Potentiometers, bwz. ein Kabelbruch am Schlei¬ feranschluß des Potentiometers trotz geringem Potentiometerstrom im Normalbetrieb sicher erkannt wird.The device according to the invention has the advantage that a missing output signal of the potentiometer, or. A cable break at the grinder connection of the potentiometer is reliably detected in normal operation despite the low potentiometer current.
Rauschspitzen, die bei Abrieb der Potentiometerbahn auftreten kön¬ nen, können besser unterdrückt-werden, bzw. durch geeignete Wahl eines Filters an einer Auswirkung am Analog-Digital-Wandler gehin¬ dert werden.Noise peaks, which can occur when the potentiometer path is abraded, can be better suppressed or prevented by an appropriate choice of a filter from having an effect on the analog-digital converter.
Durch eine eindeutige hardwaremäßige Fehlererkennung sind aufwendige und fragwürdige Plausibilitätsabfragen der Software überflüssig.Thanks to clear hardware-based error detection, complex and questionable plausibility checks of the software are unnecessary.
Vorteilhafte Weiterbildungen und Verbesserungen der erfindungsgemä¬ ßen Einrichtung sind in den Unteransprüchen angegeben.Advantageous further developments and improvements of the device according to the invention are specified in the subclaims.
Zeichnungdrawing
Figur 1 zeigt eine Prinzipdarstellung einer herkömmlichen Auswerte¬ schaltung für ein ratiometrisch ausgewertetes Drosselklappenpoten¬ tiometer, in Figur 2 ist eine erfindungsgemäße Einrichtung zur si¬ cheren Ausfallerkennung und Rauschspitzenunterdrückung für ein Dros- selklappenpotentiometer angegebenFIG. 1 shows a basic illustration of a conventional evaluation circuit for a ratiometrically evaluated throttle valve potentiometer, FIG. 2 shows a device according to the invention for reliable failure detection and noise peak suppression for a throttle valve potentiometer
Beschreibung des AusführungsbeispielesDescription of the embodiment
In der Schaltungsanordnung nach Figur 1 ist im Drosselklappengeber DKG ein Drosselklappenpotentiometer 10 zwischen die gebufferte po¬ sitive VersorgungsSpannung U , die 5 Volt beträgt, und Masse geschaltet. Im Schleifer S des Drosselklappenpotentiometers 10 sei ein eventuell kurzzeitig auftretender Rauschwiderstand vorhanden, der als Widerstand 11 dargestellt ist. Weiterhin ist im Drosselklap¬ pengeber DKG ein Schutzwiderstand 18, dessen Wert ca. 800 Ohm be¬ trägt, dem Schleifer S nachgeschaltet, wobei der anderer Anschluß des Schutzwiderstandes 18 auf den Ausgang A des Drosselklappengebers DKG führt und mit einem entsprechenden Anschluß des Steuergeräts SG verbunden ist.In the circuit arrangement according to FIG. 1, a throttle valve potentiometer 10 is located in the throttle valve generator DKG between the buffered positive supply voltage U, which is 5 volts, and ground switched. In the grinder S of the throttle valve potentiometer 10 there is possibly a short-term noise resistance, which is shown as resistor 11. Furthermore, in the throttle valve generator DKG, a protective resistor 18, the value of which is approximately 800 ohms, is connected downstream of the wiper S, the other connection of the protective resistor 18 leading to the output A of the throttle valve generator DKG and connected to a corresponding connection of the control unit SG is.
_Der betreffende Anschluß des Steuergeräts SG ist über einen Filter¬ widerstand 12 an einen, ebenfalls zwischen Versorgungsspannung und Masse liegenden Analog-Digital-Wandler 13 angeschlossen. Zwischen dem Eingang des Analog-Digital-Wandlers 13 und Masse liegt ein Fil¬ terkondensator 14, am Eingang des Steuergeräts SG liegt ein pull-down-Widerstand 15, der mit Masse verbunden ist und zur Poten¬ tialdefinition bei einem Kabelabfall dient.The relevant connection of the control unit SG is connected via a filter resistor 12 to an analog-digital converter 13 which is also between the supply voltage and ground. Between the input of the analog-digital converter 13 and ground is a filter capacitor 14, at the input of the control unit SG there is a pull-down resistor 15 which is connected to ground and is used for potential definition in the event of a cable drop.
Weiterhin ist eine Schutzbeschaltung, die aus den Zenerdioden 23 und 24 besteht, am Eingang des Analog-Digital-Wandlers 13 so angeordnet, daß sie diesen vor zu hohen positiven oder negativen Spannungsspit¬ zen schützt.Furthermore, a protective circuit, which consists of the Zener diodes 23 and 24, is arranged at the input of the analog-digital converter 13 in such a way that it protects it from excessive positive or negative voltage peaks.
Der Analog-Digital-Wandler 13 ist in Figur 1 durch eine Ersatzschal¬ tung, die aus einem Widerstand 16 und eine an Klemme 17 liegende Spannung von 2,5 Volt gebildet wird, dargestellt.The analog-to-digital converter 13 is represented in FIG. 1 by an equivalent circuit which is formed from a resistor 16 and a voltage of 2.5 volts connected to terminal 17.
Zwischen dem Schleifer S des Drosselklappenpotentiometers 10 und Masse liegt die Drosselklappenpotentiometerspannung U , über den Schleiferkontakt S fließt als Ausgangssignal des Drosselklappen¬ potentiometers der Strom I .. Am pull-down-Widerstand 15 liegt die Spannung U und am Filterkondensator 14 die Spannung U . Je nach Spannung U fließt in den Analog-Digital-Wandler 13 einThe throttle valve potentiometer voltage U lies between the wiper S of the throttle valve potentiometer 10 and ground, the current I flows as the output signal of the throttle valve potentiometer via the wiper contact S. The voltage U is at the pull-down resistor 15 and the voltage U at the filter capacitor 14. Depending on the voltage U flows into the analog-digital converter 13
Strom I,^„ von ca. +1 ,uA bis -1 ,uA und in die Schutzbeschal- ADW / / tung mit den Zenerdioden 23 und 24 ein Strom von ca. +2 uA bisCurrent I, ^ "from approx. +1, uA to -1, uA and into the protective circuit ADW / / device with the Zener diodes 23 and 24 a current of approx. +2 uA to
- 2 uA. Die Summe beider Ströme ist mit I bezeichnet. / SU- 2 uA. The sum of both currents is labeled I. / SU
Das Drosselklappenpotentiometer 10 liegt im normalen Betrieb zwi¬ schen der gebufferten Versorgungsspannung U und Masse. Die Poten¬ tiometerspannung U verändert sich je nach Stellung der Drossel¬ klappe. Die Kennlinie wird üblicherweise so ausgeführt, daß U maximal 4,8 Volt und minimal 0,2 Volt erreicht, so daß ein nicht plausibler Bereich für verschiedene Fehlerarten von Leitungskurz¬ schlüssen oder -Unterbrechungen vorhanden ist.In normal operation, the throttle valve potentiometer 10 lies between the buffered supply voltage U and ground. The potentiometer voltage U changes depending on the position of the throttle valve. The characteristic curve is usually designed in such a way that U reaches a maximum of 4.8 volts and a minimum of 0.2 volts, so that there is an implausible range for various types of faults in line shorts or interruptions.
Bei Alterung des Potentiometers treten im Schleifer Widerstände durch Abrieb der Widerstandsbahn auf, die sich insbesondere bei Be¬ wegung des Schleifers sprunghaft vergrößern. Insbesondere bei großem Strom I tritt durch den Spannungsabfall über den kurzzeitig ver¬ größerten Rauschwiderstand 18 ein hoher Spannungseinbruch am Eingang des RC-Glieds 12, 14 auf. Die Zeitkonstante dieses RC-Gliedes 12, 14 kann nur so groß gewählt werden, daß keine nennenswerte Verzögerung des Nutzsignales bei schnellster Änderung des Potentiometerschlei¬ fers im Normalbetrieb resultiert. Beispielsweise wird eine Filter- zeitkonstanteTT= 5 ms mit einem Widerstand 12 _ 12 KOh und einem Kondensator 14 mit 440 Nannofarad realisiert.When the potentiometer ages, resistances occur in the grinder due to abrasion of the resistance track, which increase suddenly, particularly when the grinder is moved. Particularly when the current I is large, the voltage drop across the briefly increased noise resistance 18 causes a high voltage dip at the input of the RC element 12, 14. The time constant of this RC element 12, 14 can only be chosen so large that there is no appreciable delay in the useful signal when the potentiometer wiper changes as quickly as possible in normal operation. For example, a filter time constant TT = 5 ms is implemented with a resistor 12 _ 12 KOh and a capacitor 14 with 440 Nannofarad.
Damit eine möglichst geringe Fehlerauswirkung am Analog-Digi- tal-Wandler 13 entsteht, muß der Strom I möglichst klein gewählt werden, damit der Spannungseinbruch so gering wie möglich gehalten wwiirrdd.. DDiiee ffoollggeennddee BBeettrraacchhttuunngg zzeeiiggtt jjeeddeoch, daß I mit einer Schaltung nach Figur 1 relativ groß wird. Zur Erkennung des Kabelabfalls am Ausgang A des Drosselklappengebers muß der Widerstand 15 das Potential soweit absenken, daß sich am Eingang des Analog-Digital-Wandlers 13 ein unplausibel niedriges Potential von beispielsweise 0,1 Volt einstellt. Durch den Strom der Zenerdiode 23 der Schutzbeschaltung und es Analog-Digital-Wandlers 13, der zusammen I = - 3 mA betragen soll, tritt ein Spannungs¬ abfall über den Widerständen 12 und 15 auf. Damit dieser kleiner als 0,1 Volt bleibt, muß der Gesamtwiderstand der beiden Widerstände 12 und 15 kleiner als 33 KOhm sein, mit einem Wert von 12 KOhm für den Widerstand 12 muß Widerstand 15 kleiner als 21 KOhm sein. Dadurch resultiert jedoch im Normalbetrieb ein hoher Schleiferstrom I von 220 uA beim oberen Abgriff der Schleiferbahn, dieser führt bei der obengenannte Erhöhung des Rauschwiderstandes 11 zu starken Span¬ nungseinbrüchen.In order that the effect of the error on the analog-digital converter 13 is as small as possible, the current I must be chosen to be as small as possible so that the voltage drop is kept as small as possible becomes relatively large. To detect the cable drop at the output A of the throttle valve sensor, the resistor 15 must lower the potential to such an extent that an implausibly low potential of, for example, 0.1 volt is set at the input of the analog-digital converter 13. A voltage drop across the resistors 12 and 15 occurs due to the current of the Zener diode 23 of the protective circuit and the analog-digital converter 13, which together should be I = -3 mA. In order for this to remain less than 0.1 volt, the total resistance of the two resistors 12 and 15 must be less than 33 KOhm, with a value of 12 KOhm for the resistor 12, resistor 15 must be less than 21 KOhm. In normal operation, however, this results in a high wiper current I of 220 µA when the wiper track is tapped at the top, which leads to sharp voltage drops when the noise resistance 11 is increased.
Figur 2 zeigt eine Schaltungsanordnung, mit der eine verbesserte Rauschspitzenunterdrückung unter Beibehaltung der Ausfallerkennung bei der Potentiometerauswertung möglich ist.FIG. 2 shows a circuit arrangement with which an improved noise peak suppression is possible while maintaining the failure detection during the potentiometer evaluation.
Das Drosselklappenpotentiometer 10 ist entsprechend der Darstellung in Figur 1 an eine gebufferte Referenzspannung U sowie an Masse angeschlossen. Der Ausgang A des Drosselklappengebers DKG ist über einen pul1-up-Widerstand 19 auf eine höhere Spannung als U ge¬ legt, beispielsweise auf 8 Volt bei U = 5 Volt. Die höhere Span¬ nung wird über einen Vorwiderstand 20, der mit einer Batteriespan¬ nungsklemme 21 verbunden ist und eine Zenerdiode 22, die zwischen dem Vorwiderstand 20 und Masse liegt, erzeugt.The throttle valve potentiometer 10 is connected to a buffered reference voltage U and to ground, as shown in FIG. The output A of the throttle valve generator DKG is connected via a pul-up resistor 19 to a higher voltage than U, for example to 8 volts at U = 5 volts. The higher voltage is generated via a series resistor 20, which is connected to a battery voltage terminal 21, and a Zener diode 22, which lies between the series resistor 20 and ground.
In einer vereinfachten Ausführungsform kann der pull-up-Widerstand 19 auch direkt auf Batteriespannung gelegt werden, also direkt an die Batteriespannungsklemme 21 angeschlossen werden. Die Eingangsbeschaltung der Schaltungsanordnung nach Figur 2, bzw. die Ausgestaltung des Drosselklappenpotentiometergebers DKG ent¬ spricht der bereits aus der Figur 1 bekannten Anordnung.In a simplified embodiment, the pull-up resistor 19 can also be connected directly to the battery voltage, that is to say can be connected directly to the battery voltage terminal 21. The input circuitry of the circuit arrangement according to FIG. 2, or the configuration of the throttle valve potentiometer transmitter DKG corresponds to the arrangement already known from FIG.
Eine Berechnung der Schaltungsanordnung nach Figur 2 zeigt die Vor¬ teile gegenüber Schaltungen nach Figur 1 auf. Um den Fehler "Kabel¬ abfall am Ausgang A des Drosselklappengebers DKG" zu erkennen, muß das Potential am Analog-Digital-Wandler-Eingang über eine Schwelle von etwa 4,9 Volt angehoben werden. In diesem Fall kann der Summen- strom von Analog-Digital-Wandler 13 und Schutzbeschaltung (Zener¬ diode 24) als I = + 3 mA angenommen werden. Der Spannungsabfall bU über den Widerständen 19 und 22 darf 8 Volt - 4,9 Volt = 3,1 Volt betragen. Damit kann der Gesamtwert der Widerstände 19 + 12 1 MOhm betragen. Da der Wert des Widerstandes 12 12 KOhm beträgt, ist er gegen den Wert des Widerstandes 19 vernachlässigbar klein, nähe¬ rungsweise gilt daß der Wert des Widerstandes 19 etwa 1 MOhm betra¬ gen darf.A calculation of the circuit arrangement according to FIG. 2 shows the advantages over the circuits according to FIG. 1. In order to detect the "Cable drop at output A of throttle valve transmitter DKG" error, the potential at the analog-digital converter input must be raised above a threshold of approximately 4.9 volts. In this case, the total current from analog-digital converter 13 and protective circuit (Zener diode 24) can be assumed to be I = + 3 mA. The voltage drop bU across resistors 19 and 22 may be 8 volts - 4.9 volts = 3.1 volts. This means that the total value of the resistors can be 19 + 12 1 MOhm. Since the value of the resistor 12 is 12 KOhm, it is negligibly small compared to the value of the resistor 19, approximately that the value of the resistor 19 may be about 1 MOhm.
Im Normalbetrieb ergibt sich der größte Schleiferstrom am unterenIn normal operation, the largest wiper current is at the bottom
Abgriff der Schleiferbahn für U 0 Volt. Über den pull-up-Wider- stand 19 fließt dann der Strom I = 7,8 Volt x 1 MOhm < 8 uA,Tapping the grinder track for U 0 volts. The current I = 7.8 volts x 1 MOhm <8 uA then flows through the pull-up resistor 19,
Pu wobei gilt, daß der Widerstand 18 viel kleiner als der Widerstand 19 ist. Der Summenstrom aus Analog-Digital-Wandler 13 und Schutzbe¬ schaltung (Zenerdiode 23 und Zenerdiode 24) beträgt: I - 3 uA.Pu where the resistance 18 is much smaller than the resistance 19. The total current from analog-digital converter 13 and protective circuit (Zener diode 23 and Zener diode 24) is: I - 3 uA.
SUSU
Der resultierende Schleiferstrom am Drosselklappenpotentiometer be¬ trägt also maximal I = - 12 uA.The resulting wiper current at the throttle valve potentiometer is a maximum of I = - 12 uA.
Mit dieser Beschaltung ist also eine Diagnosefähigkeit möglich, bei ca. 20 mal geringerem Laststrom bzw. Schleiferstrom I als bei der bekannten Anordnung nach Figur 1. Die Auswirkung von Rauschspitzen, d.h. der Spannungsabfall durch Erhöhung von Rll ist somit ebenfalls etwa 20 mal geringer als bei einer Schaltungsanordnung nach Figur 1. Als Eingangsfilter kann neben den bereits beschriebenen einfachen RC-Glied 12, 14 auch ein anderes Filter verwendet werden. Insbeson¬ dere kann direkt am Eingang, vom Verbindungspunkt von Widerstand 19 und Widerstand 12 ein zusätzlicher Kondensator 30 nach Masse ge¬ schaltet und somit die Zeitkonstante des RC-Gliedes 12, 14 verklei¬ nert werden.With this circuit, a diagnostic capability is possible, with a load current or wiper current I that is approx. 20 times lower than in the known arrangement according to FIG a circuit arrangement according to Figure 1. In addition to the simple RC elements 12, 14 already described, another filter can also be used as the input filter. In particular, an additional capacitor 30 can be connected to ground directly at the input, from the connection point of resistor 19 and resistor 12, and thus the time constant of the RC element 12, 14 can be reduced.
Bei kurzzeitig hohen Rauschwiderständen, also wenn der Wert des Wi¬ derstandes 11 gegen Unendlich geht, wird somit eine hohe Entlade- zeitkonstante über den hochohmigen Widerstand 19 erhalten, das be¬ deutet, daß auch die Sollspannung lange erhalten bleibt.In the case of briefly high noise resistances, that is to say when the value of the resistor 11 approaches infinity, a high discharge time constant is thus obtained via the high-impedance resistor 19, which means that the target voltage is also retained for a long time.
Verschwindet der Rauschwiderstand wieder, geht also der Widerstand 11 gegen Null, dann wirkt diese sehr kleine Aufladezeitkonstante über den niederohmigen Widerstand 18 auf den Sollwert U .If the noise resistance disappears again, ie the resistance 11 goes to zero, then this very small charging time constant acts on the setpoint value U via the low-resistance resistor 18.
Die in den Figuren 1 und 2 dargestellten Schaltungen können selbst¬ verständlich auch für andere Potentiometerauswertungen als für Dros¬ selklappenpotentiometerauswertungen verwendet werden. Als Beispiel sei hier ein Luftmengenmesser, der ebenfalls ein Potentiometer ent¬ hält, angegeben. The circuits shown in FIGS. 1 and 2 can of course also be used for other potentiometer evaluations than for throttle valve potentiometer evaluations. An airflow meter, which also contains a potentiometer, is given here as an example.

Claims

Ansprüche Expectations
1. Einrichtung zur sicheren Ausfallerkennung und Rauschspitzenunter¬ drückung bei einer Potentiometerauswertung, bei der das Potentio¬ meter zwischen eine Referenzspannung und Masse geschaltet wird und das am Schleiferanschluß des Potentiometers abgegriffene Signal über einen Signalpfad einem Analog-Digital-Wandler zugeführt wird, da¬ durch gekennzeichnet, daß eine gegenüber der Referenzspannung1. Device for reliable failure detection and noise peak suppression in a potentiometer evaluation, in which the potentiometer is connected between a reference voltage and ground and the signal picked up at the wiper connection of the potentiometer is fed to an analog-digital converter via a signal path, thereby characterized that one versus the reference voltage
(U ) erhöhte Spannung (U ) über einen pul1-uρ-Widerstand (19) dem Schleiferanschluß S des Potentiometers (10) zugeführt wird.(U) increased voltage (U) is fed via a pul1-uρ resistor (19) to the wiper connection S of the potentiometer (10).
2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß zwischen dem Schleiferanschluß S des Potentiometers (10) und dem Analog-Digi¬ tal-Wandler (13) ein Filter (12, 14) liegt.2. Device according to claim 1, characterized in that between the wiper connection S of the potentiometer (10) and the analog-Digi¬ tal converter (13) is a filter (12, 14).
3. Einrichtung nach Anspruch 2, 'dadurch gekennzeichnet, daß das Fil¬ ter (12, 14) ein RC-Filter ist.3. Device according to claim 2, 'characterized in that the filter (12, 14) is an RC filter.
4. Einrichtung nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß die Dimensionierung des Filters (12, 14) so vorgenommen wird, daß bei der schnellstmöglichen Änderung des am Schleifer S abgegriffenen Signals durch das Filter (12, 14) keine weitere Zeitverzögerung auf¬ tritt. 4. Device according to claim 2 or 3, characterized in that the dimensioning of the filter (12, 14) is carried out so that with the fastest possible change of the tapped signal on the grinder S by the filter (12, 14) no further time delay auf¬ occurs.
5. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch ge¬ kennzeichnet, daß das Potentiometer 10 ein Drosselklappenpotentio¬ meter oder ein Potentiometer eines Luftmengenmessers ist.5. Device according to one of the preceding claims, characterized ge indicates that the potentiometer 10 is a throttle valve potentiometer or a potentiometer of an air flow meter.
6. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch ge¬ kennzeichnet, daß der pull-up-Widerstand (19) hochohmig ist.6. Device according to one of the preceding claims, characterized ge indicates that the pull-up resistor (19) is high-impedance.
7. Einrichtung nach einem der Ansprüche 1 bis 6, dadurch gekenn¬ zeichnet, daß bei einer Unterbrechnung des Signalpfades zwischen Potentiometer (10) und Analog-Digital-Wandler (13), insbesondere am Ausgang A des Potentiometers (10), das Potential am Eingang des Ana¬ log-Digital-Wandlers (13) über einen Wert, der im ungestörten Be¬ trieb möglich ist, ansteigt und eine Erkennung der Unterbrechung er¬ möglicht.7. Device according to one of claims 1 to 6, characterized gekenn¬ characterized in that when the signal path between the potentiometer (10) and analog-digital converter (13), in particular at the output A of the potentiometer (10), the potential at Input of the analog-digital converter (13) rises above a value that is possible in undisturbed operation and enables the interruption to be detected.
8. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch ge¬ kennzeichnet, daß die Dimensionierung des Filters (12, 14) und des pull-up-Widerstandes (19) so erfolgt, daß die zulässige Dauer für Rauschspitzen möglichst groß wird.8. Device according to one of the preceding claims, characterized ge indicates that the dimensioning of the filter (12, 14) and the pull-up resistor (19) is such that the permissible duration for noise peaks is as large as possible.
9. Einrichtung nach einem der vorhergehenden Ansprüche, dadurch ge¬ kennzeichnet, daß ein zusätzlicher Filterkondensator (30) vom Ein¬ gang nach Masse geschaltet wird. 9. Device according to one of the preceding claims, characterized ge indicates that an additional filter capacitor (30) is switched from the input to ground.
PCT/DE1991/000473 1990-06-23 1991-06-05 Device for reliably detecting faults and suppressing noise peaks in potentiometer assessment WO1992000504A1 (en)

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EP0759558A2 (en) * 1995-08-18 1997-02-26 Siemens Aktiengesellschaft Testing method for an analog input channel of an analog signal detecting circuit and the corresponding analog signal detecting circuit
DE19818315C1 (en) * 1998-04-23 1999-09-16 Siemens Ag Radiometric sensor signal measuring device
DE19833413A1 (en) * 1998-07-24 2000-02-10 Siemens Ag Potentiometric sensor read-out circuit e.g. for motor vehicle IC engine accelerator pedal
DE19905071A1 (en) * 1999-02-08 2000-08-10 Siemens Ag Transmitter and method for diagnosing the supply of a transmitter
US6580277B1 (en) 1998-04-23 2003-06-17 Siemens Aktiengesellschaft Device for the ratiometric measurement of sensor signals
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FR2735871A1 (en) * 1995-06-23 1996-12-27 Renault Diagnostic method for detecting connection and wiring faults in automobile potentiometers
EP0759558A2 (en) * 1995-08-18 1997-02-26 Siemens Aktiengesellschaft Testing method for an analog input channel of an analog signal detecting circuit and the corresponding analog signal detecting circuit
EP0759558A3 (en) * 1995-08-18 1997-10-01 Siemens Ag Testing method for an analog input channel of an analog signal detecting circuit and the corresponding analog signal detecting circuit
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DE19818315C1 (en) * 1998-04-23 1999-09-16 Siemens Ag Radiometric sensor signal measuring device
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US6580277B1 (en) 1998-04-23 2003-06-17 Siemens Aktiengesellschaft Device for the ratiometric measurement of sensor signals
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DE19833413C2 (en) * 1998-07-24 2001-07-12 Siemens Ag Method for reading out at least one potentiometric sensor
DE19905071A1 (en) * 1999-02-08 2000-08-10 Siemens Ag Transmitter and method for diagnosing the supply of a transmitter
US6990967B2 (en) 2003-08-28 2006-01-31 Pierburg Gmbh Potentiometer device for determination of valve positions
EP2602695A1 (en) * 2011-12-09 2013-06-12 Thales Data input device with potentiometer and control stick for piloting an aircraft, the control stick including the data input device
FR2983987A1 (en) * 2011-12-09 2013-06-14 Thales Sa POTENTIOMETER DATA ENTRY DEVICE AND HANDLE FOR DRIVING AN AIRCRAFT, THE HAND COMPRISING THE DATA ENTRY DEVICE
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