EP 0033888 A2 19810819 - Ionisation fire alarm device with malfunction signalization.
Title (en)
Ionisation fire alarm device with malfunction signalization.
Title (de)
Ionisations-Brandmeldevorrichtung mit Störungssignalisierung.
Title (fr)
Avertisseur d'incendie à chambre d'ionisation avec signalisation de mauvais fonctionnement.
Publication
Application
Priority
DE 3004753 A 19800208
Abstract (en)
1. A fire alarm means comprising: at least one ionization fire detector (M), in particular a plurality of ionization fire detectors (M) connected parallel to each other to a detecting line (L; 10, 12) and including a measuring chamber (MK) accessible to ambient air and a reference chamber (RK) more closed against the access of ambient air, the series connection of said measuring chamber and of said reference chamber being connected to a direct current supply voltage; a smoke alarm circuit (62, 64, 66) being connected at its input side to the connection point (38) of said chambers (MK, RK) and generating a smoke alarm signal when smoke enters into said measuring chamber (MK); and a fault alarm circuit (46, 48, 50) being supplied by said direct current supply voltage, being connected at its input side to the connec tion point (38) of said chambers (MK, RK), and generating a fault alarm signal when the insula tion resistance of said measuring chamber (MK) drops below a predetermined threshold value; with the smoke alarm circuit (62, 62, 66) compris ing at its input side a field- effect transistor (90) connected with its control electrode to the con nection point (38) of said chambers (MK, RK), the drain electrode of said field-effect transistor being connected through a load resistor (92, 94) to that terminal (28) of said direct current supply voltage which said reference chamber (RK) is connected to; characterized in that for the additional emis sion of an alarm signal in case of faults influenc ing the voltage drop at said measuring chamber (MK) said fault alarm circuit (46, 48, 50) and said smoke alarm circuit (62, 64, 66) are, with respect to the input thereshold voltage necessary for their actuation and being measured between their inputs and a terminal (28, 30) of said direct current supply voltage, at least approximately voltage- independent with respect to said direct current supply voltage, that the voltage source (14) pro viding said direct current supply voltage is switch able to a voltage which is increased with respect to the nominal value of said direct current supply voltage, and that the threshold voltage of said self-locking field-effect transistor (90) is such that the voltage occuring at the control path of said field-effect transistor (90) due to the switching to the increased voltage exceeds the threshold volt age only when said measuring chamber (MK), due to the contamination of the radiation source ionizing the measuring chamber shows an inter nal resistance increased with respect to the so far undisturbed status, and that in dependency from the switching to the increased voltage the trans mission of the smoke alarm signal possibly generated by said smoke alarm circuit (62, 64, 66) to an evaluating circuit (26) is suppressed and a fault alarm signal is generated instead thereof and transmitted to the evaluating circuit (26).
Abstract (de)
Eine Brandmeldeeinrichtung umfaßt mindestens einen Ionisations-Brandmelder (M) mit einer Meßkammer (MK) und einer damit in Reihe geschalteten Referenzkammer (RK). An deren Verbindungspunkt (38) sind eine Rauchalarmschaltung (62) sowie eine Störungsalarmschaltung (46) angeschlossen, wobei die Störungsalarmschaltung (46) ein Störungsalarmsignal erzeugt, wenn der Isolationswiderstand der Meßkammer (MK) unter einen vorgegebenen Schwellenwert absinkt. Zur zusätzlichen Abgabe eines Alarmsignals beim Abfallen der Speisegleichspannung unter einen anderen vorgegebenen Schwellenwert ist die Störungsalarmschaltung (46) hinsichtlich der zu ihrem Ansprechen erforderlichen Eingangs-Schwellenspannung gegenüber der Speisegleichspannung zumindest annähernd spannungsunabhängig ausgebildet.
IPC 1-7
IPC 8 full level
G08B 17/10 (2006.01); G08B 17/11 (2006.01); G08B 29/00 (2006.01); G08B 29/04 (2006.01)
CPC (source: EP)
G08B 17/11 (2013.01); G08B 29/04 (2013.01)
Designated contracting state (EPC)
AT DE FR GB IT NL
DOCDB simple family (publication)
EP 0033888 A2 19810819; EP 0033888 A3 19821103; EP 0033888 B1 19850116; EP 0033888 B2 19910206; AT E11346 T1 19850215; DE 3004753 A1 19810827; DE 3004753 C2 19831222; DE 3168215 D1 19850228; FR 2475768 A1 19810814; FR 2475768 B1 19830923
DOCDB simple family (application)
EP 81100552 A 19810126; AT 81100552 T 19810126; DE 3004753 A 19800208; DE 3168215 T 19810126; FR 8102439 A 19810206