Siemens Aktiengesellschaft

Uwe Metzner

Peer Thilo

Peter Kupec

Herbert Foissner

At a security fence comprising a plurality of electrodes disposed in parallel, a transmitter applies an alternating voltage to at least one of the electrodes. Remaining electrodes are grounded as receive electrodes. An ammeter measures electrode current and a measured value corresponding to an operating capacitance of this electrode is acquired and provided in every electrode circuit. Disruption factors are compensated on the basis of these measured values by means of comparison to earlier measured values of the same or of the other electrodes and by means of comparison to specific measured value patterns. An alarm is triggered only given non-compensatable measured values.

Method and arrangement for measuring changes of capacitive state at a

An electrode arrangement for capacitive guard fences wherein the conductor is horizontally stretched substantially parallel to the ground has a shape for preventing formation of water droplets which may collect as a result of precipitation from generating a false alarm and which also deters small animals from perching on the electrode. In one embodiment the electrode has a rectangular cross-section with the longest sides of the electrode being disposed substantially vertically. In another embodiment the electrode consists of two conductors having circular cross-sections which may be disposed parallel to one another or twisted. A further electrode embodiment has at least three conductors having very small circular cross-sections disposed at equal intervals from one another around a circular circumference. Means for facilitating water droplet runoff are provided at equal intervals which simultaneously serve as spacers for the conductors. Another electrode embodiment has a single line wire in the shape of a stretched helical spring.

Electrode arrangement for capacitive guard fences

A plurality of transmitters operating at respective frequencies is connected to at least some electrodes of a capacitive security fence. Each electrode is provided with a transformer whose primary winding is connected between the transmitter and ground. The secondary of each transformer is connected to a plurality of bandpass filters having adjustable center frequencies which correspond to the transmitter frequencies. The voltage available at the outputs of the bandpass filters are fed to a measuring device and supplied to a microcomputer. The interelectrode capacitances and the self-capacitances of the electrodes of the system are identified from the measured voltages which are proportional to the capacitances.

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Munich, Germany

Uwe Metzner