Cerberus Ag

Peter Christen

Bernhard Durrer

Peter Muller

Arnim Sauerbrey

Hansheinrich Brandli

A gas sensing signaling system is provided in which a plurality of gas sensing units are connected over cables with a central station. To permit establishment of threshold levels such that false alarms are rejected while the system still remains sensitive to dangerous conditions and to permit ready supervision and testing of said system, a central station is provided in which timing circuits are included which start the time interval upon sensing of an alarm condition above a lower, or warning threshold level. If the lower warning level signal persists for the timing interval--for example for about one-half minute, a warning signal is given. A higher level signal generates an alarm signal, either immediately or after a much shorter time delay. The circuit includes self-holding circuitry so that, once a sensing unit transmits a sensing signal which persists beyond the previous predetermined warning or alarm time duration, the central station will indicate the respective conditions until manually reset. Besides indication, corrective action, such as energization of ventilation equipment and the like can be controlled. The cabling system preferably operates with predetermined, discrete voltage levels at the respective signal lines which, upon transmission of a warning and/or alarm signal, changes under control of a voltage control circuit in the central station, to permit additionally, by connection of a termination element, to indicate malfunction within the lines or the sensing units by detecting current flow and voltage relationships in the respective lines.

Gas sensing signaling system

A gas sensing unit designed to be protected against explosions and serving for the detection of combustible gases in an atmosphere, containing a gas sensor functioning according to the principle of catalytic oxidation or a semiconductor gas sensor. The gas sensing unit contains, within a housing, at least two mutually separated chambers or spaces. The one chambr is a compression-proof space and contains an electronic evaluation circuit for the gas sensor, the other chamber, which is a space structured to be protected against explosions, contains the gas sensor and a balancing element and is separated from the atmosphere by a sintered metal bushing or sleeve. A third explosion-proof chamber or space can be provided in the gas sensing unit for the purpose of connecting the lines or conductors. The gas sensor together with the balancing adapter forms an assembly or unit which can be pluggably arranged in the cover of the chamber containing the electronic system or hardware. With such type gas sensing unit it is possible to easily exchange the gas sensor at its erection site, without the need for having to open the compression-proof chamber containing the electronic components. The testing and balancing of the gas sensor can be accomplished at the manufacturing plant.

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Mannedorf, Switzerland

Peter Christen