Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Reexamination Certificate
2000-12-13
2003-06-24
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
C324S073100, C340S003100, C340S003510, C340S505000, C340S514000
Reexamination Certificate
active
06583628
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
BACKGROUND OF THE INVENTION
The invention relates to a process and device to determine malfunctioning detectors acting as current sinks in a danger signaling system. Danger signaling systems, e.g. fire alarm installations, as a rule, include a major number of danger detectors which are connected to a two-wire signaling line. This one may be conceived as a stub-end feeder or a ring circuit via which the individual detectors communicate with a control centre. Each detector has a sensor or the like which, in dependence on parameters in its bypass, produces measured values which are transferred to the control centre through the line. In order to associate the measured values with the individual detectors, it is necessary to assign an identifier or address to each detector. This one is saved in a non-volatile memory.
From DE 196 34 099 A1, a process for the bidirectional data transfer to a bus between the control centre and the detectors has become known wherein the control centre represents the master and the detectors represent the slaves and the transfer of data sequences from the master to the slaves is effected via an impressed voltage and the slaves, while emitting signals, exhibit the behaviour of current sinks. For an increase in the coverage of transfer from the slaves to the master, a bit-synchronous process is proposed for the data transfer. The document further states that the behaviour of the bidirectional data transfer is of a direction-dependent asymmetry in transfer quality. While the transfer via an impressed voltage from the master to the slaves is effected with no damping as a consequence of the current-reducing behaviour of the slaves and, therefore, is termed to be of a high degree of quality and a low susceptibility to malfunctions and a wide coverage the transfer via an impressed current from the slaves to the master is of a lower quality. Some of the causes are that the data bits undergo significant changes due to the noise in the data transfer channel. As another cause, the capacitance per unit length for the data transfer channel is mentioned, which leads to a power division so that only a fraction of the rise in power generated by the slaves arrives at the master (control centre).
Even more disadvantageous than the aforementioned influences, which mainly can be attributed to the line parameters and can have adverse effects on the quality of data transfer, can heavy current sinks prove to be. A current sink can already be provoked by a detector which has become defective during its long-term service. In view of the huge number of fire detectors which are in continuous operation by day and night, a frequently occurring case for detectors in danger signaling systems, despite all provisions made, it cannot be prevented that an individual component fails in one of the lot of detectors at a non-foreseeable time, specifically following a long period of service. If this component should increase the current flow of the detector by an inadmissible degree in an uninfluenceable, permanent way this can have an annoying effect on the flow of data. The implications which can be imagined are differently intense and may range from the malfunction of only one detector up to the failure of the whole data traffic throughout the signaling line.
In the state of the art, there is a number of differently configured signaling systems. From EP 0 111 178 A1, it has become known to open a series switch by means of an interrogation voltage jump generated by the control centre to a first value and, after a time determined by the state of the detector, to step the series switch through to the next detector by means of another interrogation voltage jump to a second value. These electric signals which correspond to the detector states will be evaluated only within preset ranges of time in the control centre. The ranges of time therebetween are defined as malfunction bands. Signals which are within these malfunction bands cause a respective malfunction message in the control centre. The chain-like step-through also serves for a detection of a short-circuit towards the succeeding detector. The point of the short-circuit may be localized and, hence, the malfunction may be remedied rapidly. In spite of the short-circuit, the complete operating voltage is maintained in the whole signaling line. Only that portion of the signaling line in which the short-circuit exists will be switched off. This document also mentions the use of digital data for the transfer which, however, is refused because its susceptibility to malfunctions.
From DE 33 46 527 A1, a process has become known for an anti-malfunction evaluation of an alarm in a signaling line of a danger signaling system wherein signaling-line states are evaluated in a control centre by means of a window discriminator disposed in the control centre. A disturbance-variable mask-out digital device connected downstream of the window discriminator, upon appearance of the threshold signal, periodically checks over a preset period whether the threshold signal still is applied. Not until this preset time has lapsed an output signal is provided to a detector evaluation device where the test procedure is discontinued once the event disappears and is re-started once a new threshold signal is applied. The known process is unsuitable for a bidirectional digital transfer at a high data frequency.
To achieve a higher reliability of data transfer in danger signaling systems it has been known, from DE 42 12 440 A1 to dispose a transfer malfunction determining system between the control centre and the detector. The transfer of data in the known system is as follows: Emission of access data in the form of a voltage from the control centre through a first transfer line, sending back of reply data of a detector, as is determined in the access data, in the form of an electric current through a second transfer line during a reply time period in which the data sent back from the detector unit which has replied to the access data emitted by the control centre are formed from state data of the detector and check sum data which were compiled by adding the detector state data to the proper address data; the control centre adds the address data to detector state data, a determination is made as to whether a error in transfer has occurred if the data determined by this addition are not in agreement with the check sum data. The known process is intended to primarily aid in preventing a noise in the transfer lines from making itself felt as a malfunction.
From DE 25 33 382 C1, a process for the automatic allocation of detector addresses in a danger signaling system has become known. In this process, the detectors are stepped through in a chain-like manner for the purpose of address assignment wherein the value measured is determined from the delay in time up to the switch-on of the succeeding detector. The step-through is carried out by the switches which are included in the path of a supply line and exist in every detector. The detector address is determined from the value of the preceding rise in line current. Whenever an interrogation cycle begins the detectors are disconnected from the signaling line by a change in voltage.
Finally, from DE 40 38 992 C1, a process has become known for the automatic allocation of detector addresses in danger signaling systems in which each detector has a transfer device, a measured-value memory, an address memory, and a voltage measuring device as well as a switch between the wires of the signaling line. In a first phase, the control centre applies a high voltage to the line, which supplies the detectors with energy by charging a capacitor. In a second phase, a short-circuiting voltage is applied to the line, which causes all detectors the address memories of which are empty to short out the line by means of their switch. In a third phase, a measuring current is impressed into the line and the voltage which will thereby
Deb Anjan K.
Job Lizenz GmbH & Co. KG
Le N.
Vidas Arrett & Steinkraus P.A.
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