EP0030621B1 - Ionisationsrauchmelder mit erhöhter Betriebssicherheit - Google Patents

Ionisationsrauchmelder mit erhöhter Betriebssicherheit Download PDF

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Publication number
EP0030621B1
EP0030621B1 EP80106923A EP80106923A EP0030621B1 EP 0030621 B1 EP0030621 B1 EP 0030621B1 EP 80106923 A EP80106923 A EP 80106923A EP 80106923 A EP80106923 A EP 80106923A EP 0030621 B1 EP0030621 B1 EP 0030621B1
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EP
European Patent Office
Prior art keywords
voltage
transistor
operating voltage
resistor
circuit element
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP80106923A
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German (de)
English (en)
French (fr)
Other versions
EP0030621A1 (de
Inventor
Andreas Scheidweiler
Peter Müller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Cerberus AG
Original Assignee
Cerberus AG
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Filing date
Publication date
Application filed by Cerberus AG filed Critical Cerberus AG
Priority to AT80106923T priority Critical patent/ATE11345T1/de
Publication of EP0030621A1 publication Critical patent/EP0030621A1/de
Application granted granted Critical
Publication of EP0030621B1 publication Critical patent/EP0030621B1/de
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas

Definitions

  • the present invention relates to an ionization smoke detector with at least one low-voltage ionization chamber with a measuring and counterelectrode sensor, to which chamber the surrounding air has practically free access and which has at least one radioactive source for generating ions, and an electrical circuit for Alarm triggering, which has a first switching element controlled by the voltage drop across the ionization chamber, which becomes conductive when a certain smoke density is exceeded, and a second switching element, which becomes conductive when the first switching element becomes conductive and triggers an alarm signal, soft detectors via lines to a detector operating voltage to the Lines emitting signal center is connected.
  • ionization smoke detectors are the most widespread early warning detectors.
  • the main advantages of this type of detector include its universal applicability and its simple and robust mechanical construction. Since the detectors must respond quickly and safely in the event of a fire, but on the other hand they must not trigger false alarms, high demands are placed on their reliability.
  • Fig. 1 shows the circuit of a typical low-voltage smoke detector, in which the mession chamber is operated in series with a load resistor, preferably a saturated reference chamber. The connection point of the two chambers is connected to the control electrode of a cold cathode tube. The voltage drop across the measuring chamber is approx. 80 V in the idle state. If smoke enters the measuring chamber, this voltage increases by approx. 50 V and thus reaches the ignition voltage of the cold cathode tube. This leads to the triggering of a current flow between the anode and cathode, which can be evaluated via a relay for triggering the alarm.
  • the chamber voltage of approx. 100 V required to operate the low-voltage ionization smoke detectors means that high electrical field strengths of a few 100 V / cm occur at the measuring electrode.
  • the dust particles that are always present in the air are therefore deposited electrostatically on the electrodes, which means that the electrodes are covered with a gradually thicker layer of dust. If these dusts are electrically non-conductive material, which is often the case especially in the dry winter periods, the ion current in the measuring chamber is blocked and a false alarm can be triggered. This means that the detectors have to be cleaned frequently, which is very expensive.
  • ionization smoke detectors that are operated with an operating voltage of ⁇ 50 V.
  • a low voltage type ionization fire detector is described, for example, in US Pat. No. 3,521,263.
  • Fig. Shows the circuit of a typical low-voltage ionization smoke detector.
  • the voltage across the measuring chamber is also the gate voltage for a field effect transistor. It is selected so that the transistor is de-energized in the idle state.
  • the controlled rectifier (SCR) is thus also blocked and the relay is not energized. If flue gases enter the measuring chamber, the chamber voltage increases and, if a certain threshold value is exceeded, the SCR is ignited, which triggers the relay alarm.
  • the object of the present invention is to remedy the above-mentioned disadvantages of the known ionization smoke detectors and, in particular, to create an ionization smoke detector with increased operational reliability, which reduces the tendency to contamination and thus the susceptibility to faults of the detectors due to a low field strength in the ionization chamber, so that the service intervals are long can be selected that requires a smaller amount of radioactive material compared to the high-voltage detectors and that is insensitive to electromagnetic interference.
  • the converter is designed such that the sensor operating voltage is at least ten times lower than the detector operating voltage.
  • the first switching element has a field effect transistor blocked in the idle state, the gate electrode of which is connected to the measuring electrode of the ionization chamber, so that the field effect transistor becomes conductive when a certain smoke density is exceeded;
  • the second switching element has a cold cathode tube as a bistable switching element, the control voltage of which is kept below the ignition voltage of the control electrode of the cold cathode tube by a switch in the idle state;
  • the ionization smoke detector has means which actuate the switch when the field effect transistor is opened such that the control voltage of the cold cathode tube slowly increases until the ignition voltage is reached and the cold cathode tube ignites.
  • the switch consists of a transistor which conducts and is saturated in the idle state, a capacitor being connected between the collector and emitter of the transistor and a resistor being connected between the collector of the transistor and the anode of the cold cathode tube , wherein the time constant R x C> 2 s, preferably> 5 s and in particular> 10 s.
  • the converter consists of a resistor, a zener diode and the base-emitter path of the transistor.
  • FIG. 3 shows an example of an ionization smoke detector according to the invention.
  • a mession chamber MK accessible to the outside atmosphere is in series with a load resistance R 6 .
  • the connection point between the mession chamber MK and load resistor R 6 is connected to the gate electrode G of a field effect transistor T 1 , the drain-source path of the FET T is connected in parallel with the Z-diode ZD 1 to the measurement chamber load resistance path.
  • the low voltage output of the converter T is connected both to one electrode of the measuring chamber MK and to a discriminator D, which is used to control a switch S which is connected to the control electrode St of the cold cathode tube KR, which is connected between the lines L, and L z , acts.
  • the control electrode St of the cold cathode tube KR is connected to the output L of the switch S via the resistor R 2 to the line L 1 and via the capacitor C to the line L z .
  • the discriminator D is designed in such a way that, when the sensor operating voltage U 2 falls below a certain threshold value, it actuates the switch S, the output of which, in the idle state, holds the control electrode voltage U St of the cold cathode tube KR below the ignition voltage (preferably more than 50 V below) in such a way that the capacitor C can charge via the resistor R 2 until the ignition voltage is reached and the cold cathode tube KR is ignited.
  • the current rise that occurs in lines L 1 and L 2 can be evaluated in the signaling center as an alarm signal.
  • FIG. 1 A preferred embodiment of a circuit of an ionization smoke detector according to the invention is explained in more detail in FIG.
  • the working resistance R a lying in series with the measuring chamber MK is designed as a reference ionization chamber RK that is difficult to access from the outside atmosphere and operates in the saturation region.
  • the detector operating voltage U 1 is supplied to a voltage stabilizer circuit consisting of a resistor R 1, a Zener diode ZD 2 and the base-emitter path of a transistor T 2 .
  • This voltage stabilizer circuit provides the for the operation of the low voltage necessary sensor operating voltage U 2 .
  • the FET T switches through and an additional current flows through the resistor R,.
  • the sensor operating voltage U 2 is reduced to such an extent that the Zener voltage of the Zener diode ZD 2 is undershot, as a result of which the base current of the transistor T 2 is interrupted so that it blocks.
  • the capacitor C is charged via the resistor R 2 . If the voltage U St across the capacitor C reaches the ignition voltage of the cold cathode tube KR, it ignites and a strong current flows through the lines L ,, L 2 ; this current flow can be evaluated in alarm center Z.
  • the time constant of the element R z , C is selected such that after the transistor T 2 is blocked, the ignition voltage of the control electrode St is only reached after approximately 2 seconds. Short-term electrical disturbances, which lead to the opening of the field effect transistor T, do not trigger an alarm since the ignition voltage of the cold cathode tube KR is not reached. While the charging of the capacitor C takes place slowly via the resistor R 2 , an immediate discharge of the capacitor C is carried out when the field effect transistor T is closed, since this is short-circuited via the transistor T 2 .
  • the time constant can be adjusted by changing the R 2 and / or C operating conditions of the smoke detector, for example, several seconds or set to about ten seconds. Repeated short bursts of smoke, such as those caused by heavy tobacco smoke, cannot lead to a false alarm, since the charges C cannot accumulate due to the immediate discharge of the charges.
  • Zener diode ZD 2 is placed between the emitter of the transistor T 2 and the line L 2 and the base of the transistor T 2 is connected directly to the point A.
  • the resistor R 5 can thus be omitted.
  • the open circuit voltage at the control electrode St of the cold cathode tube KR corresponds approximately to the Zener voltage, and a lower collector-emitter voltage at the transistor T 2 is required for the ignition of the cold cathode tube.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
EP80106923A 1979-12-14 1980-11-10 Ionisationsrauchmelder mit erhöhter Betriebssicherheit Expired EP0030621B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80106923T ATE11345T1 (de) 1979-12-14 1980-11-10 Ionisationsrauchmelder mit erhoehter betriebssicherheit.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH11077/79 1979-12-14
CH1107779 1979-12-14

Publications (2)

Publication Number Publication Date
EP0030621A1 EP0030621A1 (de) 1981-06-24
EP0030621B1 true EP0030621B1 (de) 1985-01-16

Family

ID=4369809

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80106923A Expired EP0030621B1 (de) 1979-12-14 1980-11-10 Ionisationsrauchmelder mit erhöhter Betriebssicherheit

Country Status (7)

Country Link
US (1) US4364031A (enrdf_load_stackoverflow)
EP (1) EP0030621B1 (enrdf_load_stackoverflow)
JP (1) JPS5694497A (enrdf_load_stackoverflow)
AT (1) ATE11345T1 (enrdf_load_stackoverflow)
CA (1) CA1148279A (enrdf_load_stackoverflow)
DE (1) DE3069987D1 (enrdf_load_stackoverflow)
YU (1) YU314380A (enrdf_load_stackoverflow)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH681932A5 (enrdf_load_stackoverflow) * 1990-12-04 1993-06-15 Cerberus Ag
JP3128633B2 (ja) * 1992-05-25 2001-01-29 能美防災株式会社 イオン化式煙感知器
FR2872914B1 (fr) * 2004-07-07 2006-10-13 Univ Rennes I Etablissement Pu Capteur pour la detection et/ou la mesure d'une concentration de charges electriques contenues dans une ambiance, utilisations et procede de fabrication correspondants
WO2008034080A2 (en) * 2006-09-15 2008-03-20 Nano-Proprietary, Inc. Smoke detector
DE102014019773B4 (de) 2014-12-17 2023-12-07 Elmos Semiconductor Se Vorrichtung und Verfahren zur Unterscheidung von festen Objekten, Kochdunst und Rauch mittels des Displays eines Mobiltelefons
DE102014019172B4 (de) 2014-12-17 2023-12-07 Elmos Semiconductor Se Vorrichtung und Verfahren zur Unterscheidung von festen Objekten, Kochdunst und Rauch mit einem kompensierenden optischen Messsystem

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295121A (en) * 1961-12-30 1966-12-27 Danske Securitas As Electric alarm system, preferably for fire alarms
US3872449A (en) * 1973-03-30 1975-03-18 Cerberus Ag Fire detector and method employing assymetrical integrator
FR2299879A1 (fr) * 1975-02-10 1976-09-03 Hochiki Co Circuit de sortie d'un detecteur de fumee a ionisation

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB831812A (en) 1957-02-01 1960-03-30 Minerva Detector Company Ltd Improvements in or relating to fire detectors
CH446131A (de) * 1966-02-22 1967-10-31 Cerberus Ag Ionisationsfeuermelderanlage
JPS446089Y1 (enrdf_load_stackoverflow) * 1966-03-30 1969-03-05
CH489070A (de) * 1969-03-27 1970-04-15 Cerberus Ag Werk Fuer Elektron Ionisationsfeuermelder
US3657713A (en) * 1969-06-02 1972-04-18 Nittan Co Ltd Device for testing ionization smoke detector
US3797008A (en) * 1971-02-04 1974-03-12 Nittan Co Ltd Fire detecting system
US4017852A (en) * 1976-06-24 1977-04-12 Honeywell Inc. Apparatus for supervising leads interconnecting a plurality of self-contained abnormal condition sensing and alarm annunciating units

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3295121A (en) * 1961-12-30 1966-12-27 Danske Securitas As Electric alarm system, preferably for fire alarms
US3872449A (en) * 1973-03-30 1975-03-18 Cerberus Ag Fire detector and method employing assymetrical integrator
FR2299879A1 (fr) * 1975-02-10 1976-09-03 Hochiki Co Circuit de sortie d'un detecteur de fumee a ionisation

Also Published As

Publication number Publication date
JPS6242320B2 (enrdf_load_stackoverflow) 1987-09-08
CA1148279A (en) 1983-06-14
ATE11345T1 (de) 1985-02-15
YU314380A (en) 1983-10-31
DE3069987D1 (en) 1985-02-28
JPS5694497A (en) 1981-07-30
US4364031A (en) 1982-12-14
EP0030621A1 (de) 1981-06-24

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