EP0239807B1 - Capacitive intrusion protection system - Google Patents

Capacitive intrusion protection system Download PDF

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Publication number
EP0239807B1
EP0239807B1 EP87102947A EP87102947A EP0239807B1 EP 0239807 B1 EP0239807 B1 EP 0239807B1 EP 87102947 A EP87102947 A EP 87102947A EP 87102947 A EP87102947 A EP 87102947A EP 0239807 B1 EP0239807 B1 EP 0239807B1
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EP
European Patent Office
Prior art keywords
current
measuring
cable
electrode
winding
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Expired - Lifetime
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EP87102947A
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German (de)
French (fr)
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EP0239807A1 (en
Inventor
Uwe Metzner
Peer Dr. Ing. Thilo
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Siemens AG
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Siemens AG
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Priority to AT87102947T priority Critical patent/ATE62766T1/en
Publication of EP0239807A1 publication Critical patent/EP0239807A1/en
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/26—Electrical actuation by proximity of an intruder causing variation in capacitance or inductance of a circuit

Definitions

  • the invention relates to a capacitive intrusion protection system according to the preamble of claim 1.
  • the electrodes are connected to the evaluation device via cables, generally coaxial cables.
  • the capacities or changes in capacitance between the transmitting and receiving electrodes and / or also between the transmitting electrodes and the earth (earth potential) are measured and alarm criteria for an alarm are derived therefrom.
  • the currents flowing over the electrode capacitance are measured and evaluated. For example, such a method is described in DE-A-33 29 554. There, the electrode currents are measured to measure the capacitive state changes on a protective fence in each electrode circuit with the aid of current measuring devices, and the respective operating capacity of the electrode is obtained therefrom.
  • EP-A-131 738 has therefore already proposed a measuring arrangement for capacitance measurement in which the disruptive influences caused by the cable capacitances are avoided.
  • additional and return lines are provided for each electrode, which are connected to the electrode via additional transmitters.
  • the object of the invention is therefore to avoid the disadvantages described above and for a capacitive intrusion protection system a measuring arrangement for measuring the transmission currents in the electrode circuit to be specified in which the cable capacities have no disruptive influence on the measurement result. Neither expensive special cables nor complex circuit arrangements should be used.
  • a current measuring device is arranged in the transmission circuit between the transmitter and the coaxial conductor of the connecting line, that a further current measuring device is arranged between the shield conductor of the connecting line and the earth potential, and in that the difference from the measuring current and the cable current flowing through the cable capacitance is formed and the actually determined electrode current is processed further.
  • both currents are measured individually.
  • the cable current is eliminated by the difference formation, so that the electrode current actually flowing over the electrodes is measured and evaluated.
  • the current measured in each case can advantageously be converted with an analog-digital converter and the difference can be formed in a connected microcomputer.
  • a specially designed measuring transducer can be provided as the measuring device for measuring the measuring current flowing in the coaxial conductor and for measuring the cable current via the shield conductor.
  • the primary winding is arranged in the electrode circuit. The current to be measured or the associated current is fed via the secondary winding proportional voltage tapped.
  • an additional, third winding is arranged in the transducer, which is connected on the one hand to the shield conductor of the coaxial connecting line and on the other hand is at ground potential. This additional winding leads the cable current in such a way that it is subtracted from the original measuring current. It is thereby achieved in a simple but advantageous manner that the cable current flowing over the unavoidable cable capacities no longer interferes with the measurement.
  • the primary winding and the additional third winding have the same number of turns, so that the cable current flowing through the third winding flows counter to the actual measuring current and is subtracted in this way. The current actually flowing to earth via the electrode capacity is therefore measured on the secondary winding.
  • a measuring transducer MW with its primary winding PW is arranged in the electrode circuit in the evaluation device AWE.
  • the transducer is connected to the transmitter SEN, which for example generates an AC voltage US of 100 volts.
  • the second terminal of the transmitter is at ground potential EP.
  • the measuring current IM which is measured via the secondary winding SW of the measuring transducer MW, flows into the coaxial conductor KL of the connecting line VL, for example in the form of a proportional voltage there can be tapped.
  • the measured current IM consists of the sum of the electrode current IE flowing via the electrode E and the electrode capacitance CE to the earth point EP and the cable current IK flowing via the cable capacitance CK to the screen Sch of the coaxial cable or earth potential EP.
  • the measured current value is falsified depending on the cable capacity CK.
  • a first measuring device MIM is arranged in the electrode circuit, ie between the transmitter SEN and the coaxial conductor KL of the connecting line VL.
  • the shield conductor Sch of the coaxial connecting line VL is not directly grounded, but leads to the evaluation device AWE.
  • the shield conductor Sch is connected to a further measuring device MIK, which is connected to earth potential EP with its second connection.
  • the cable current IK is subtracted from the measurement current IM via a subtraction device located in the evaluation device, so that the electrode current IE actually flowing through the electrode E and electrode capacitance CE is measured.
  • FIG. 3 A simple exemplary embodiment of the arrangement according to the invention is shown in FIG. 3.
  • the measuring device ME is formed by a measuring transducer MW which, in addition to the known primary winding PW in the electrode circuit and the secondary winding SW, has a third winding W3 for tapping the measuring current IM. 2
  • this third winding W3 is connected to the shield conductor Sch of the coaxial connecting line VL, via which the cable current IK caused by the cable capacitance CK flows.
  • the other end of the third winding W3 is at ground potential EP.
  • the number of turns of the primary winding PW and the third additional winding W3 are of equal size, so that the additional winding W3 is flowed through in the opposite direction and the interfering cable current IK is subtracted from the measuring current IM, so that the electrode current IE actually to be measured is determined.
  • the arrangement according to the invention is used in a capacitive intrusion protection system for a plurality of electrodes which are fed by a transmitter and in which the electrode currents are measured in order to determine the electrode capacities.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Burglar Alarm Systems (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Measuring Instrument Details And Bridges, And Automatic Balancing Devices (AREA)

Abstract

The system has a multiplicity of electrodes (E) which are connected to an evaluation unit (AWE) by coaxial cables (VL). A measuring unit (MIM) arranged in the electrode circuit is used to measure the current (IM) flowing from the generator (SEN) to the electrode (E). Another measuring unit (MIK), in the evaluation unit (AWE), measures the cable current (IK) flowing through the cable capacitance (CK), the screen conductor (Sch) of the coaxial cable (VL) being connected to earth potential (EP) via the measuring unit (MIK). The difference between the measured current (IM) and the cable current (IK) gives the actual electrode current (IE). The ammeters (MIM, MIK) can consist of an instrument transformer (MW) having a third winding (W3) with the same number of turns as the primary winding (PW). The primary winding (PW) is in the electrode circuit, the third winding (W3) is connected between the screen conductor (Sch) and earth potential (EP). <IMAGE>

Description

Die Erfindung bezieht sich auf ein kapazitives Intrusionsschutzsystem gemäß dem Oberbegriff des Anspruchs 1.The invention relates to a capacitive intrusion protection system according to the preamble of claim 1.

Bei kapazitiven Intrusionsschutzsystemen sind die Elektroden über Kabel, im allgemeinen Koaxialkabel, mit der Auswerteeinrichtung verbunden. Zur Erfassung von Eindringlingen werden die Kapazitäten bzw. Kapazitätsänderungen zwischen Sende- und Empfangselektroden und/oder aber auch zwischen den Sendeelektroden und der Erde (Erdpotential) gemessen und daraus Alarmkriterien für einen Alarm abgeleitet. Zur Erfassung der Elektrodenkapazitäten werden die über die Elektrodenkapazität fließenden Ströme gemessen und bewertet. Beispielsweise ist in der DE-A- 33 29 554 ein derartiges Verfahren beschrieben. Dort werden zur Messung der kapazitiven Zustandsänderungen an einem Schutzzaun in jedem Elektrodenstromkreis mit Hilfe von Strommeßeinrichtungen die Elektrodenströme gemessen und daraus die jeweilige Betriebskapazität der Elektrode gewonnen. Insbesondere bei längeren Verbindungsleitungen zwischen den einzelnen Elektroden und der Auswerteeinrichtung überlagern sich zu den gemessenen Strömen in der Auswerteeinrichtung störende Ströme, die durch die Kabelkapazität fließen und dadurch das Meßergebnis verfälschen. Dies führt in nachteiliger Weise zu Falschmessungen und dadurch häufig zu Fehlalarmen.In the case of capacitive intrusion protection systems, the electrodes are connected to the evaluation device via cables, generally coaxial cables. In order to detect intruders, the capacities or changes in capacitance between the transmitting and receiving electrodes and / or also between the transmitting electrodes and the earth (earth potential) are measured and alarm criteria for an alarm are derived therefrom. In order to record the electrode capacities, the currents flowing over the electrode capacitance are measured and evaluated. For example, such a method is described in DE-A-33 29 554. There, the electrode currents are measured to measure the capacitive state changes on a protective fence in each electrode circuit with the aid of current measuring devices, and the respective operating capacity of the electrode is obtained therefrom. Particularly in the case of longer connecting lines between the individual electrodes and the evaluation device, interfering currents which flow through the cable capacitance and are superimposed on the measured currents in the evaluation device thereby falsifying the measurement result. This disadvantageously leads to incorrect measurements and therefore often to false alarms.

In der EP-A-131 738 wurde daher schon eine Meßanordnung zur Kapazitätsmessung vorgeschlagen, bei der die störenden Einflüsse durch die Kabelkapazitäten vermieden werden. Bei der dort beschriebenen Anordnung sind für jede Elektrode zusätzliche und Rückleitungen vorgesehen, die über zusätzliche Übertrager an der Elektrode angeschlossen sind. Diese Maßnahmen sind sehr aufwendig und verteuern derartige Intrusionsschutzsysteme.EP-A-131 738 has therefore already proposed a measuring arrangement for capacitance measurement in which the disruptive influences caused by the cable capacitances are avoided. In the arrangement described there, additional and return lines are provided for each electrode, which are connected to the electrode via additional transmitters. These measures are very complex and make intrusion protection systems more expensive.

Ferner ist bekannt, kurze kapazitätsarme Kabel zu verwenden, um die störenden Einflüsse genügend klein zu halten. Dies hat aber den Nachteil, daß die Einsatzmöglichkeiten im Falle von kürzeren Verbindungskabeln eingeschränkt sind, und daß andererseits das Intrusionsschutzsystem mit teueren Spezialkabeln sehr verteuert wird. Da diese störenden Einflüsse insbesondere durch die Sendeströme, da hier hohe Spannungen anliegen, verursacht werden, hat man schon auf die Messung der Sendeströme verzichtet. Dies wiederum führt zu beträchtlichen Informationsverlusten, so daß ein zuverlässiges Auswerten und ein sicheren Ansprechen des Intrusionsschutzsystems nicht immer gewährleistet ist.It is also known to use short, low-capacity cables in order to keep the interfering influences sufficiently small. However, this has the disadvantage that the possible uses in the case of shorter connecting cables are restricted, and that, on the other hand, the intrusion protection system with expensive special cables is very expensive. Since these disturbing influences are caused in particular by the transmission currents, since high voltages are present here, the measurement of the transmission currents has already been dispensed with. This in turn leads to considerable loss of information, so that reliable evaluation and reliable response of the intrusion protection system is not always guaranteed.

Aufgabe der Erfindung ist es daher, die oben geschilderten Nachteile zu vermeiden und für ein kapazitives Intrusionsschutzsystem eine Meßanordnung zur Messung der Sendeströme im Elektrodenstromkreis anzugeben, bei dem die Kabelkapazitäten keinen störenden Einfluß auf das Meßergebnis haben. Dabei sollen weder teuere Spezialkabel noch aufwendige Schaltungsanordnungen verwendet werden.The object of the invention is therefore to avoid the disadvantages described above and for a capacitive intrusion protection system a measuring arrangement for measuring the transmission currents in the electrode circuit to be specified in which the cable capacities have no disruptive influence on the measurement result. Neither expensive special cables nor complex circuit arrangements should be used.

Diese Aufgabe wird erfindungsgemäß bei einem eingangs geschilderten Intrusionsschutzsystem dadurch gelöst, daß im Sendestromkreis zwischen dem Sender und dem Koaxialleiter der Verbindungsleitung eine Strommeßeinrichtung angeordnet ist, daß zwischen dem Schirmleiter der Verbindungsleitung und dem Erdpotential eine weitere Strommeßeinrichtung angeordnet ist, und daß die Differenz aus dem Meßstrom und dem durch die Kabelkapazität fließenden Kabelstrom gebildet und der tatsächlich ermittelte Elektrodenstrom weiterverarbeitet wird.This object is achieved in an intrusion protection system described in the introduction in that a current measuring device is arranged in the transmission circuit between the transmitter and the coaxial conductor of the connecting line, that a further current measuring device is arranged between the shield conductor of the connecting line and the earth potential, and in that the difference from the measuring current and the cable current flowing through the cable capacitance is formed and the actually determined electrode current is processed further.

Bei der erfindungsgemäßen Meßanordnung werden beide Ströme einzeln gemessen. Durch die Differenzbildung wird der Kabelstrom eliminiert, so daß der tatsächlich über die Elektroden fließende Elektrodenstrom gemessen und ausgewertet wird.In the measuring arrangement according to the invention, both currents are measured individually. The cable current is eliminated by the difference formation, so that the electrode current actually flowing over the electrodes is measured and evaluated.

Dabei kann in vorteilhafter Weise der jeweils gemessene Strom mit einem Analog-Digital-Wandler umgesetzt werden und die Differenz in einem angeschlossenen Mikrorechner gebildet werden.The current measured in each case can advantageously be converted with an analog-digital converter and the difference can be formed in a connected microcomputer.

In einer zweckmäßigen Ausgestaltung der Erfindung kann als Meßeinrichtung zur Messung des im Koaxialleiter fließenden Meßstroms und zur Messung des Kabelstroms über den Schirmleiter ein besonders ausgebildeter Meßwandler vorgesehen sein. Die Primärwicklung ist dabei, wie bekannt, im Elektrodenstromkreis angeordnet. Über die Sekundärwicklung wird der zu messende Strom oder die dazu proportionale Spannung abgegriffen. Erfindungsgemäß ist eine zusätzliche, dritte Wicklung im Meßwandler angeordnet, die einerseits am Schirmleiter der koaxialen Verbindungsleitung angeschlossen ist und andererseits auf Erdpotential liegt. Durch diese zusätzliche Wicklung wird der Kabelstrom derart geführt, daß er vom ursprünglichen Meßstrom subtrahiert wird. Dadurch wird in einfacher jedoch vorteilhafter Weise erreicht, daß der über die unvermeidbaren Kabelkapazitäten fließende Kabelstrom die Messung nicht mehr störend beeinflußt. Erfindungsgemäß weist dabei die Primärwicklung und die zusätzliche dritte Wicklung die gleiche Windungszahl auf, so daß der durch die dritte Wicklung fließende Kabelstrom entgegen dem eigentlichen Meßstrom fließt und auf die Weise subtrahiert wird. Es wird daher an der Sekundärwicklung der tatsächlich über die Elektrodenkapazität zur Erde fließende Strom gemessen.In an expedient embodiment of the invention, a specially designed measuring transducer can be provided as the measuring device for measuring the measuring current flowing in the coaxial conductor and for measuring the cable current via the shield conductor. As is known, the primary winding is arranged in the electrode circuit. The current to be measured or the associated current is fed via the secondary winding proportional voltage tapped. According to the invention, an additional, third winding is arranged in the transducer, which is connected on the one hand to the shield conductor of the coaxial connecting line and on the other hand is at ground potential. This additional winding leads the cable current in such a way that it is subtracted from the original measuring current. It is thereby achieved in a simple but advantageous manner that the cable current flowing over the unavoidable cable capacities no longer interferes with the measurement. According to the invention, the primary winding and the additional third winding have the same number of turns, so that the cable current flowing through the third winding flows counter to the actual measuring current and is subtracted in this way. The current actually flowing to earth via the electrode capacity is therefore measured on the secondary winding.

Anhand der Figuren wird die Erfindung im folgenden kurz erläutert. Dabei zeigen

  • Fig. 1 eine bekannte Meßanordnung,
  • Fig. 2 die erfindungsgemäße Meßanordnung und
  • Fig. 3 die erfindungsgemäße Meßanordnung mit einem Meßwandler.
The invention is briefly explained below with reference to the figures. Show
  • 1 shows a known measuring arrangement,
  • Fig. 2 shows the measuring arrangement according to the invention and
  • Fig. 3 shows the measuring arrangement according to the invention with a transducer.

In Fig. 1 ist im Elektrodenstromkreis in der Auswerteeinrichtung AWE ein Meßwandler MW mit seiner Primärwicklung PW angeordnet. Der Meßwandler ist am Sender SEN angeschlossen, der beispielsweise eine Wechselspannung US von 100 Volt erzeugt. Der Sender liegt mit seinem zweiten Anschluß auf Erdpotential EP. In den Koaxialleiter KL der Verbindungsleitung VL fließt der Meßstrom IM, der über die Sekundärwicklung SW des Meßwandlers MW gemessen, beispielsweise in Form einer proportionalen Spannung dort abgegriffen werden kann. Der gemessene Strom IM besteht jedoch aus der Summe des über die Elektrode E und die Elektrodenkapazität CE zum Erdpunkt EP fließenden Elektrodenstroms IE und dem über die Kabelkapazität CK zum Schirm Sch des Koaxialkabels bzw. Erdpotential EP fließenden Kabelstroms IK. In Abhängigkeit von der Kabelkapazität CK wird der gemessene Stromwert verfälscht.1, a measuring transducer MW with its primary winding PW is arranged in the electrode circuit in the evaluation device AWE. The transducer is connected to the transmitter SEN, which for example generates an AC voltage US of 100 volts. The second terminal of the transmitter is at ground potential EP. The measuring current IM, which is measured via the secondary winding SW of the measuring transducer MW, flows into the coaxial conductor KL of the connecting line VL, for example in the form of a proportional voltage there can be tapped. However, the measured current IM consists of the sum of the electrode current IE flowing via the electrode E and the electrode capacitance CE to the earth point EP and the cable current IK flowing via the cable capacitance CK to the screen Sch of the coaxial cable or earth potential EP. The measured current value is falsified depending on the cable capacity CK.

In der in Fig.2 dargestellten erfindungsgemäßen Meßanordnung ist im Elektrodenstromkreis, also zwischen dem Sender SEN und dem Koaxialleiter KL der Verbindungsleitung VL eine erste Meßeinrichtung MIM angeordnet. Der Schirmleiter Sch der koaxialen Verbindungsleitung VL ist nicht unmittelbar geerdet, sondern führt zur Auswerteeinrichtung AWE. Dort ist der Schirmleiter Sch an einer weiteren Meßeinrichtung MIK angeschlossen, die mit ihrem zweiten Anschluß auf Erdpotential EP liegt. Über eine in der Auswerteeinrichtung befindliche Subtrahiereinrichtung wird der Kabelstrom IK vom Meßstrom IM subtrahiert, so daß der tatsächlich über die Elektrode E und Elektrodenkapazität CE fließende Elektrodenstrom IE gemessen wird.In the measuring arrangement according to the invention shown in FIG. 2, a first measuring device MIM is arranged in the electrode circuit, ie between the transmitter SEN and the coaxial conductor KL of the connecting line VL. The shield conductor Sch of the coaxial connecting line VL is not directly grounded, but leads to the evaluation device AWE. There, the shield conductor Sch is connected to a further measuring device MIK, which is connected to earth potential EP with its second connection. The cable current IK is subtracted from the measurement current IM via a subtraction device located in the evaluation device, so that the electrode current IE actually flowing through the electrode E and electrode capacitance CE is measured.

Ein einfaches Ausführungsbeispiel für die erfindungsgemäße Anordnung ist in Fig. 3 dargestellt. Dort ist in der Auswerteeinrichtung AWE die Meßeinrichtung ME von einem Meßwandler MW gebildet, der neben der bekannten Primärwicklung PW im Elektrodenstromkreis und der Sekundärwicklung SW zum Abgreifen des Meßstroms IM eine dritte Wicklung W3 aufweist. Diese dritte Wicklung W3 ist entsprechend der Fig. 2 einerseits am Schirmleiter Sch der koaxialen Verbindungsleitung VL angeschlossen, über den der durch die Kabelkapazität CK hervorgerufene Kabelstrom IK fließt. Das andere Ende der dritten Wicklung W3 liegt auf Erdpotential EP. Die Windungszahlen der Primärwicklung PW und der dritten zusätzlichen Wicklung W3 sind gleich groß, so daß die Zusatzwicklung W3 entgegengesetzt durchströmt wird und der störende Kabelstrom IK vom Meßstrom IM subtrahiert wird, so daß der tatsächlich zu messende Elektrodenstrom IE ermittelt wird.A simple exemplary embodiment of the arrangement according to the invention is shown in FIG. 3. There, in the evaluation device AWE, the measuring device ME is formed by a measuring transducer MW which, in addition to the known primary winding PW in the electrode circuit and the secondary winding SW, has a third winding W3 for tapping the measuring current IM. 2, on the one hand, this third winding W3 is connected to the shield conductor Sch of the coaxial connecting line VL, via which the cable current IK caused by the cable capacitance CK flows. The other end of the third winding W3 is at ground potential EP. The number of turns of the primary winding PW and the third additional winding W3 are of equal size, so that the additional winding W3 is flowed through in the opposite direction and the interfering cable current IK is subtracted from the measuring current IM, so that the electrode current IE actually to be measured is determined.

Mit der erfindungsgemäßen Anordnung werden ausschließlich die Elektrodenströme IE gemessen, auch wenn die Elektroden E über lange Verbindungskabel VL mit den Auswerteeinrichtungen AwE verbunden sind. Die erfindungsgemäße Anordnung wird bei einem kapazitiven Intrusionsschutzsystem für mehrere Elektroden angewandt, die von einem Sender gespeist werden und bei denen die Elektrodenströme zur Ermittlung der Elektrodenkapazitäten gemessen werden.With the arrangement according to the invention, only the electrode currents IE are measured, even if the electrodes E are connected to the evaluation devices AwE via long connecting cables VL. The arrangement according to the invention is used in a capacitive intrusion protection system for a plurality of electrodes which are fed by a transmitter and in which the electrode currents are measured in order to determine the electrode capacities.

Claims (3)

  1. Capacitive intrusion protection system in which the currents flowing across the electrode capacitance are evaluated to earth and in which the electrodes (E) are connected via coaxial connecting lines (VL) to an evaluation device (AWE) in which the respective electrode currents (IE) are measured with measuring devices (ME) arranged in the connecting lines (VL), a current measuring device (MIM) being arranged in the transmitting current circuit between the transmitter (SEN) and the coaxial conductor (KL) of the connecting line (VL), and the other side of the transmitter (SEN) forming a voltage source being connected to earth (EP), characterised in that a further current measuring device (MIK) is arranged between the shielding conductor (Sch) of the connecting line (VL) and the earth potential (EP), and in that the difference between the measuring current (IM) and the cable current (IK) caused by the cable capacitance (CK) is formed and the electrode current (IE) actually identified is further processed.
  2. Capacitive intrusion protection system according to Claim 1, characterised in that the respectively measured measuring and cable currents (IM and IK) are digitised and further processed in a microcomputer.
  3. Capacitive intrusion protection system according to Claim 1, characterised in that the current measuring devices (MIM, MIK) are formed by a measuring transducer (MW) which, in addition to the primary winding (PW) which is situated in the transmitting current circuit and to the secondary winding (SW) at which the measuring current (IM) is tapped off, has a third winding (W3) which is situated between the shielding conductor (Sch) of the connecting line (VL) and earth potential (EP), the primary winding (PW) and the third winding (W3) having identical numbers of turns and being flowed through in opposite directions.
EP87102947A 1986-03-04 1987-03-02 Capacitive intrusion protection system Expired - Lifetime EP0239807B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87102947T ATE62766T1 (en) 1986-03-04 1987-03-02 CAPACITIVE INTRUSION PROTECTION SYSTEM.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3607017 1986-03-04
DE3607017 1986-03-04

Publications (2)

Publication Number Publication Date
EP0239807A1 EP0239807A1 (en) 1987-10-07
EP0239807B1 true EP0239807B1 (en) 1991-04-17

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EP87102947A Expired - Lifetime EP0239807B1 (en) 1986-03-04 1987-03-02 Capacitive intrusion protection system

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EP (1) EP0239807B1 (en)
AT (1) ATE62766T1 (en)
DE (1) DE3769348D1 (en)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5432459A (en) * 1992-03-17 1995-07-11 Conmed Corporation Leakage capacitance compensating current sensor for current supplied to medical device loads with unconnected reference conductor
AU671902B2 (en) * 1993-06-01 1996-09-12 Conmed Corporation Current sensor for medical devices with continuity monitor
FR3107286B1 (en) * 2020-02-13 2022-04-01 Univ Reims Champagne Ardenne Method for detecting the modification of the environment of a cable

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1104868B (en) * 1959-03-06 1961-04-13 Telefonbau Electrical room protection system
US4293852A (en) * 1978-12-08 1981-10-06 Lawrence Security Services Ltd. Capacitive article removal alarm
DE3321471A1 (en) * 1983-06-14 1984-12-20 Siemens AG, 1000 Berlin und 8000 München MEASURING ARRANGEMENT FOR DETERMINING OWN CAPACITY OR CHANGING IT TO A CAPACITIVE FENCE
DE3329554A1 (en) * 1983-08-16 1985-03-07 Siemens AG, 1000 Berlin und 8000 München METHOD AND ARRANGEMENT FOR MEASURING CAPACITIVE STATE CHANGES ON A PROTECTIVE FENCE

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ATE62766T1 (en) 1991-05-15
EP0239807A1 (en) 1987-10-07
DE3769348D1 (en) 1991-05-23

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