EP0130992B1 - Photoelectric smoke detector - Google Patents

Photoelectric smoke detector Download PDF

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Publication number
EP0130992B1
EP0130992B1 EP83902981A EP83902981A EP0130992B1 EP 0130992 B1 EP0130992 B1 EP 0130992B1 EP 83902981 A EP83902981 A EP 83902981A EP 83902981 A EP83902981 A EP 83902981A EP 0130992 B1 EP0130992 B1 EP 0130992B1
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EP
European Patent Office
Prior art keywords
signal
circuit
radiation
smoke
smoke detector
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
EP83902981A
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German (de)
French (fr)
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EP0130992A1 (en
Inventor
Hannes Güttinger
Martin Labhart
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Cerberus AG
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Cerberus AG
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/185—Signal analysis techniques for reducing or preventing false alarms or for enhancing the reliability of the system
    • 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
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/20—Calibration, including self-calibrating arrangements
    • G08B29/22—Provisions facilitating manual calibration, e.g. input or output provisions for testing; Holding of intermittent values to permit measurement
    • 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
    • G08B17/113—Constructional details

Definitions

  • the invention relates to a photoelectric smoke detector according to the preamble of claim 1.
  • a smoke detector is known from EP-A-0 011 205.
  • the smoke detector can e.g. be designed as a scattered radiation detector, in which the radiation scattered on smoke particles is evaluated, or as a radiation extinction detector, which uses radiation attenuation or absorption by smoke particles, or also as a photoacoustic smoke detector, in which the smoke particles emit acoustic impulses when absorbed by radiation impulses, which are emitted by an acoustic -electric converters are converted into electrical impulses, such as in EP-A-0 014 251.
  • the smoke detector can serve as a smoke sensor in which the value of the smoke signal emitted is a measure of the smoke density, or as a smoke detector which signals the occurrence of a certain smoke density.
  • electromagnetic radiation which is to be understood as visible light, infrared or ultraviolet radiation
  • a measurement volume e.g. by means of a light-emitting diode (LED)
  • the radiation scattered on smoke particles in the measurement volume is picked up by a scatter radiation receiver arranged outside the radiation range of the radiation source, and by means of an evaluation circuit, a smoke alarm signal is given if the scatter radiation level exceeds a certain threshold.
  • LED light-emitting diode
  • a crucial problem here is to ensure that a smoke alarm signal is only triggered by scattered radiation from smoke particles, but not by interfering radiation entering the measurement volume, which is also picked up by the radiation receiver and simulates the presence of radiation-scattering smoke particles. This is particularly important for smoke detectors in which only a limited radiation intensity is available in the measurement volume, for example in smoke detectors in which the radiation is guided into and removed from the measurement volume by means of radiation-conducting elements or fiber optics, e.g. described in DE-A-30 37 636.
  • the object of the invention is to avoid the aforementioned disadvantages of the prior art and, moreover, to provide a photoelectric smoke detector which, with very low smoke densities, has a greater sensitivity even with reduced radiation intensity and power and has improved immunity to interference.
  • the invention is defined in more detail in the characterizing part of claim 1.
  • a detector unit D is radiation-conducting elements or light guides L, and L 2 connected to an evaluation circuit A.
  • the type of light guide is expediently adapted to the radiation used.
  • a plurality of detector units can also be connected in parallel to the evaluation circuit A by means of the same light guide via known branching elements or by means of different light guides.
  • a control circuit 1 provided in the evaluation circuit A intermittently controls a radiation source 2 designed as a radiation-emitting diode LED, for example with a frequency of 0.1-40 kHz.
  • the switch-on time is preferably of the same order of magnitude as the switch-off time.
  • the radiation emitted by the radiation source 2 depending on the type of LED visible light, infrared or ultraviolet radiation, is coupled into the light guide L, and guided via this to the detector unit D.
  • a collimation device 4 is arranged, ie a special optic that collimates the radiation emerging from the light guide into an at least approximately parallel radiation beam.
  • a further collimation device 6 whose reception area is oriented in such a way that it receives radiation scattered on smoke particles from a scattering volume 7 and feeds the input 8 of a second light guide L 2 , which feeds the received scattered radiation from a solar cell 9.
  • This solar cell converts the received radiation, ie the optical signal, into an electrical signal, which is amplified by a receiving amplifier 10.
  • the amplifier output signal is received by a signal processing circuit which, on the other hand, receives a reference signal from the control circuit 1 via a line 12 and which only forwards a signal to the downstream display circuit 13 when the emitted and received radiation are in coincidence.
  • This display circuit 13 when used as a smoke sensor, indicates the smoke concentration according to the value of the scattered radiation signal, or it triggers an alarm device 14, when used as a fire detector, if the scattered radiation signal exceeds a predetermined threshold, and thus indicates a fire outbreak.
  • FIG. 2 shows the construction of the detector unit D of a scattered radiation smoke detector which is particularly suitable for fire detection.
  • a plastic base plate 20 carries an air-permeable housing 21 enclosing the measuring chamber M and a support element 22 inside.
  • a known connection or plug connection C is provided in the base plate 20, which is used to connect the light guides L and L 2 to the light guide Connections 23 and 28 inside the detector is used, the ends of which interact with the collimation devices 24 and 26.
  • a plurality of diaphragms 25 for shielding the residual radiation from the collimator 26 are placed in the central part of the carrier element.
  • the optical arrangement in the interior of the housing 21 is surrounded by an air-permeable, but radiation-absorbing, labyrinth-like element 27, which can have nested slats or radiation-absorbing ribs 29 on the surfaces, for example.
  • a suitable radiation trap 30 can be provided to catch the direct radiation, as well as a corresponding radiation trap 31 at the end of the reception area.
  • the invention is particularly advantageous for those detector units in which the supply and signal transmission is carried out by means of optical fibers or fiber optics, where usually only a small radiation power is available, it also proves to be particularly advantageous in the case of classic smoke detectors with electrical transmission , especially when a particularly high sensitivity is required, ie when the lowest smoke concentrations are to be detected.
  • the radiation source 2 takes the place of the device 4
  • the radiation receiver 9 takes the place of the device 6, and the light guide connections L 1 and L 2 are omitted.
  • the construction of such smoke detectors can be carried out, for example, in accordance with US Pat. No. 4,181,439.
  • FIG. 3 shows an example of a signal processing circuit 11 suitable for the smoke detector according to FIGS. 1 and 2.
  • the output signal of the receiver amplifier and signal converter 10 is fed via a low-noise preamplifier 15 to a frequency filter 16, which is preferably transparent to the frequency of the control circuit 1 and dampens the noise.
  • Preamplifier 15 and frequency filter 16 can also be combined to form a frequency-selective amplifier.
  • the filtered signal arrives at a phase-sensitive circuit 17, which on the other hand is controlled by the control circuit 1 via a trigger circuit 32 and a phase shifter 33.
  • This phase-sensitive circuit 17 has the effect that the polarity of the signal coming from the receiver 10 is maintained, or vice versa, depending on the phase position of the alternating signal of the control circuit 1.
  • the polarity is maintained during the switch-on phases of the radiation source, ie the receiver signal is passed on unchanged, but vice versa during the switch-off phases in between, ie a positive signal is converted into a negative one and vice versa a negative signal is turned into a positive one.
  • That so changed output signal of the phase-sensitive circuit 17 now arrives at a downstream integration circuit 18 with a predetermined time constant, which can be adjustable, for example by means of a capacitor 19.
  • the entire signal processing circuit 11 can also be designed as a single hybrid circuit or a corresponding device, for example as so-called lock-in amplifier.
  • the phase-sensitive circuit 17 receives the amplified signal a of the control circuit 1 at its control input, with the phase shifter 33 being able to correct any phase shifts in the receiver signal during signal passage, and the amplified and filtered receiver signal b at its signal input.
  • the output signal c of the phase-sensitive circuit 17 appears at the output and is integrated by the integration circuit 18 into an output signal d. No scattered radiation is received during the period X.
  • the signal b is then a pure noise signal without any frequency component of the control circuit 1.
  • the rate of increase is determined by the time constant of the integration circuit 18 and can be adapted to the expected interference frequency by a suitable choice or setting of the time constant, so that a certain increase is achieved by a certain number of successive synchronous receiver pulses, but never by irregularly occurring interference pulses becomes.
  • a predefined threshold d o ie the alarm threshold is reached, a.
  • Display circuit 13 controlled in a known manner, which triggers a visual, acoustic or electrical alarm signal.
  • the circuit can be simplified if the control voltage output by the control circuit 1 is rectangular.
  • the alternating signal coming out of the circuit 32 designed as a simple frequency filter fluctuates periodically back and forth between the extreme values (+1) and (-1).
  • the phase-sensitive circuit can then be designed as a simple multiplication circuit 17, since the alternating multiplication by (+1) and (-1) has exactly the required effect, namely the polarity reversal of the signal in the rhythm of the control signal.
  • the invention has been described above using a scattered radiation smoke detector.
  • the inventive idea can be analog, with similar advantages also with other types of photoelectric smoke detectors, such as Use radiation absorbance or photoacoustic smoke detectors.
  • the adjustment measures required for this are familiar to the person skilled in the art.
  • it can be achieved that a display or an alarm signal with exceptional security is only triggered if the receiver signal is exactly synchronous, i.e. is absolutely the same frequency and in phase with the signal controlling the radiation source, but no other interference signals.
  • the circuit also works safely and reliably when the receiver signal is extremely weak and the noise completely covers the useful signal, so that lower smoke concentrations can be detected or measured than before.
  • the invention deliberately deviates from the previous tendency, which is obvious to the person skilled in the art, to improve the signal / noise ratio by increasing the radiation pulse height and reducing the radiation pulse width.
  • the circuit according to the invention works with particular advantage even in cases where it is expedient or necessary to choose the pulse widths in the same order of magnitude as the intermediate times.
  • the smoke detector described preferably serves as a fire detector, but is also suitable for other uses, e.g. for smoke gas monitoring, smoke density measurement etc.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

In a photoelectric smoke detector, a radiation source (2) is intermittently actuated by a control unit (1) and the radiation on which smoke particles have an influence, for example the diffused radiation, is picked up by a radioreceiver (9). The signal from the radioreceiver (9) is supplied to a signal processing unit (11) simultaneously actuated by the control unit (1) having a phase sensitive unit which reverses the received signal according to the phase position of the signal from the control unit (1) and supplies the signal thus modified to an integration unit of which the integrated output signal actuates a display unit (13); the latter may for example provide an alarm signal when the integrated signal, that is the fume density, exceeds a predetermined threshold value, or may display the smoke density. Thereby, low smoke signals may be safely and reliably detected, even when they are completely covered by background noise. Such a fume detector may be conveniently used as a sensitive and reliable fire warning device.

Description

Die Erfindung betrifft einen photoelektrischen Rauchdetektor gemäss dem Oberbegriff des Anspruch 1. Ein solcher Rauchdetektor ist aus der EP-A- 0 011 205 bekannt.The invention relates to a photoelectric smoke detector according to the preamble of claim 1. Such a smoke detector is known from EP-A-0 011 205.

Der Rauchdetektor kann dabei z.B. als Streustrahlungsdetektor ausgebildet sein, bei dem die an Rauchpartikeln gestreute Strahlung ausgewertet wird, oder als Strahlungsextinktionsdetektor, der die Strahlungsschwächung oder Absorption durch Rauchpartikel ausnützt, oder auch als photoakustischer Rauchdetektor, bei dem die Rauchpartikel bei Absorption von Strahlungsimpulsen akustische Impulse abgeben, die von einem akustisch-elektrischen Wandler in elektrische Impulse umgesetzt werden, wie z.B. in der EP-A- 0 014 251 beschrieben. Der Rauchdetektor kann als Rauchsensor dienen, bei dem der Wert des abgegebenen Rauchsignales ein Mass für die Rauchdichte ist, oder als Rauchmelder, der das Auftreten einer bestimmten Rauchdichte signalisiert.The smoke detector can e.g. be designed as a scattered radiation detector, in which the radiation scattered on smoke particles is evaluated, or as a radiation extinction detector, which uses radiation attenuation or absorption by smoke particles, or also as a photoacoustic smoke detector, in which the smoke particles emit acoustic impulses when absorbed by radiation impulses, which are emitted by an acoustic -electric converters are converted into electrical impulses, such as in EP-A-0 014 251. The smoke detector can serve as a smoke sensor in which the value of the smoke signal emitted is a measure of the smoke density, or as a smoke detector which signals the occurrence of a certain smoke density.

Bei solchen Rauchdetektoren, beispielsweise den in der PCT-Anmeldung WO 80/01326 beschriebenen Streustrahlungs-Rauchdetektoren, die vorzugsweise zur Brandmeldung dienen, wird elektromagnetische Strahlung, worunter sichtbares Licht, Infrarot-oder Ultraviolett-Strahlung zu verstehen ist, in ein Messvolumen eingestrahlt, z.B. mittels einer lichtemittierenden Diode (LED), und die an Rauchpartikeln im Messvolumen gestreute Strahlung von einem ausserhalb des Strahlungsbereiches der Strahlungsquelle angeordneten Streustrahlungsempfänger aufgenommen, und mittels einer Auswerteschaltung wird ein Rauchalarmsignal gegeben, wenn das Streustrahlungsniveau eine bestimmte Schwelle übersteigt.In such smoke detectors, for example the stray radiation smoke detectors described in PCT application WO 80/01326, which are preferably used for fire detection, electromagnetic radiation, which is to be understood as visible light, infrared or ultraviolet radiation, is radiated into a measurement volume, e.g. by means of a light-emitting diode (LED), and the radiation scattered on smoke particles in the measurement volume is picked up by a scatter radiation receiver arranged outside the radiation range of the radiation source, and by means of an evaluation circuit, a smoke alarm signal is given if the scatter radiation level exceeds a certain threshold.

Ein entscheidendes Problem ist es hierbei, sicherzustellen, dass ein Rauchalarmsignal nur durch Streustrahlung an Rauchpartikeln ausgelöst wird, jedoch nicht durch in das Messvolumen eindringende Störstrahlung, die ebenfalls vom Strahlungsempfänger aufgenommen wird und die Anwesenheit strahlungsstreuender Rauchpartikel vortäuscht. Besonders wichtig ist dies bei Rauchdetektoren, bei denen nur eine beschränkte StrahlungsIntensität im Messvolumen zur Verfügung steht, beispielsweise bei Rauchdetektoren, bei denen die Strahlung mittels strahlungsleitender Elemente oder Fiber-Optik in das Messvolumen geleitet und daraus abgenommen wird, wie z.B. in der DE-A- 30 37 636 beschrieben.A crucial problem here is to ensure that a smoke alarm signal is only triggered by scattered radiation from smoke particles, but not by interfering radiation entering the measurement volume, which is also picked up by the radiation receiver and simulates the presence of radiation-scattering smoke particles. This is particularly important for smoke detectors in which only a limited radiation intensity is available in the measurement volume, for example in smoke detectors in which the radiation is guided into and removed from the measurement volume by means of radiation-conducting elements or fiber optics, e.g. described in DE-A-30 37 636.

Um eine falsche Rauchsignalgabe durch Störstrahlung zu verhindern, ist es bereits bekannt, z.B. aus den EP-A- 00 11 205 oder EP-A-00 14 779, die Strahlungsquelle nur in sehr kurzzeitigen Impulsen zu betreiben und den Strahlungsempfänger an eine Koinzidenzschaltung anzuschliessen, die nur dann ein Rauchsignal erzeugt, wenn Streustrahlung während der kurzzeitigen Strahlungsimpulse empfangen wird, jedoch nicht bei Auftreten von Störstrahlungsimpulsen in den Zwischenzeiten. Der seltene Fall, dass ein Störimpuls in der kurzen Zeit eines Strahlungsimpulses eintrifft, kann dabei durch eine Repetierschaltung bzw. Integrationsstufe eliminiert werden, die nur dann ein Rauchsignal weiter gibt, wenn mehrere Koinzidenzen hintereinander auftreten.In order to prevent false smoke signaling by interference radiation, it is already known, e.g. from EP-A-00 11 205 or EP-A-00 14 779 to operate the radiation source only in very short-term pulses and to connect the radiation receiver to a coincidence circuit which only generates a smoke signal if stray radiation is received during the short-term radiation pulses , but not when interference radiation pulses occur in the meantime. The rare case that an interference pulse arrives in the short time of a radiation pulse can be eliminated by a repeater circuit or integration stage that only passes on a smoke signal if several coincidences occur in succession.

Mit derartigen Auswerteschaltungen lässt sich eine störungsunanfällige Brandmeldung erreichen, sofern ausreichend intensive Strahlungsimpulse zur Verfügung stehen. Viele Strahlungsquellen lassen jedoch nur eine beschränkte Maximalintensität ohne Schädigung oder schnelle Alterung zu, und bei Fiberoptik- Übertragung erfolgt eine Strahlungsdämpfung, so dass es zweckmässig oder notwendig ist, längere Einschaltzeiten der Strahlungsquelle zu wählen, um eine genügende Streustrahlungs-Leistung zu bekommen. Die beschriebenen Auswerteschaltungen arbeiten hier nicht mehr ausreichend störsicher, einerseits da das Auftreten von Störimpulsen in den Einschalt-Intervallen viel wahrscheinlicher wird, andererseits da beim Strahlungsempfänger das Signal/Rausch-Verhältnis so klein werden kann, dass einzelne Rausch-Impulse das Signal-Niveau erreichen und ein fehlerhaftes Signal auslösen können. Besonders geringe Rauchkonzentrationen, bei denen das Signal innerhalb des Rauschpegels liegt, konnten auf diese Weise überhaupt nicht detektiert werden, d.h. die Empfindlichkeit von Brandmeldern mit solchen Auswerteschaltungen war begrenzt.With such evaluation circuits, a fire alarm that is not susceptible to faults can be achieved, provided that sufficiently intense radiation pulses are available. However, many radiation sources only allow a limited maximum intensity without damage or rapid aging, and radiation is attenuated in the case of fiber-optic transmission, so that it is expedient or necessary to select longer switch-on times for the radiation source in order to obtain sufficient scattered radiation power. The evaluation circuits described here are no longer sufficiently immune to interference, on the one hand because interference pulses in the switch-on intervals are much more likely, on the other hand because the signal-to-noise ratio in the radiation receiver can become so low that individual noise pulses reach the signal level and can trigger a faulty signal. Particularly low smoke concentrations at which the signal is within the noise level could not be detected at all in this way, i.e. the sensitivity of fire detectors with such evaluation circuits was limited.

Die Erfindung hat die Aufgabe, die erwähnten Nachteile des Standes der Technik zu vermeiden und darüber hinaus einen photoelektrischen Rauchdetektor zu schaffen, der bei sehr geringen Rauchdichten eine grössere Ansprechempfindlichkeit auch bei verminderter Strahlungsintensität und Leistung hat und eine verbesserte Störsicherheit aufweist.The object of the invention is to avoid the aforementioned disadvantages of the prior art and, moreover, to provide a photoelectric smoke detector which, with very low smoke densities, has a greater sensitivity even with reduced radiation intensity and power and has improved immunity to interference.

Die Erfindung ist im kennzeichnenden Teil des Anspruch 1 näher definiert.The invention is defined in more detail in the characterizing part of claim 1.

Die Erfindung sowie zweckmässige und vorteilhafte Weiterbildungen derselben werden an Hand der in den Figuren wiedergegebenen Ausführungsbeispiele und Diagramme erläutert.

  • Figur 1 zeigt ein Beispiel eines Blockschaltschemas eines Streustrahlungs-Rauchdetektors,
  • Figur 2 zeigt ein Beispiel für den konstruktiven Aufbau eines Streustrahlungs-Rauchdetektors,
  • Figur 3 zeigt eine für die Rauchdetektoren nach Figur 1 und 2 geeignete Signalverarbeitungsschaltung, und
  • Figur 4 zeigt den zeitlichen Verlauf der an verschiedenen Punkten der Signalverarbeitungsschaltung nach Figur 3 auftretenden Signale.
The invention as well as expedient and advantageous developments of the same are explained on the basis of the exemplary embodiments and diagrams shown in the figures.
  • FIG. 1 shows an example of a block circuit diagram of a scattered radiation smoke detector,
  • FIG. 2 shows an example of the construction of a stray radiation smoke detector,
  • FIG. 3 shows a signal processing circuit suitable for the smoke detectors according to FIGS. 1 and 2, and
  • FIG. 4 shows the time course of the signals occurring at different points in the signal processing circuit according to FIG. 3.

Bei dem in Figur 1 wiedergegebenen Ausführungsbeispiel eines photoelektrischen Rauchdetektors ist eine Detektoreinheit D mittels strahlungsleitender Elemente oder Lichtleiter L, und L2 an eine Auswerteschaltung A angeschlossen. Die Art der Lichtleiter ist dabei zweckmässigerweise an die verwendete Strahlung angepasst. Es können auch mehrere Detektoreinheiten mittels derselben Lichtleiter über bekannte Verzweigungselemente oder mittels verschiedener Lichtleiter parallel an die Auswerteschaltung A angeschlossen sein. In der dargestellten Anordnung steuert eine in der Auswerteschaltung A vorgesehene Steuerschaltung 1 eine als strahlungsemittierende Diode LED ausgebildete Strahlungsquelle 2 intermittierend an, beispielsweise mit einer Frequenz von 0.1 - 40 kHz. Die Einschaltzeit liegt dabei vorzugsweise in der gleichen Grössenordnung wie die Ausschaltzeit. Die von der Strahlungsquelle 2 ausgesandte Strahlung, je nach LED-Typ sichtbares Licht, Infrarot- oder Ultraviolett-Strahlung wird in den Lichtleiter L, eingekoppelt und über diesen zur Detektoreinheit D geleitet.In the exemplary embodiment of a photoelectric smoke detector shown in FIG. 1, a detector unit D is radiation-conducting elements or light guides L, and L 2 connected to an evaluation circuit A. The type of light guide is expediently adapted to the radiation used. A plurality of detector units can also be connected in parallel to the evaluation circuit A by means of the same light guide via known branching elements or by means of different light guides. In the arrangement shown, a control circuit 1 provided in the evaluation circuit A intermittently controls a radiation source 2 designed as a radiation-emitting diode LED, for example with a frequency of 0.1-40 kHz. The switch-on time is preferably of the same order of magnitude as the switch-off time. The radiation emitted by the radiation source 2, depending on the type of LED visible light, infrared or ultraviolet radiation, is coupled into the light guide L, and guided via this to the detector unit D.

Am Ausgang 3 dieses Lichtleiters ist eine Kollimations-Einrichtung 4 angeordnet, d.h. eine spezielle Optik, die die aus dem Lichtleiter austretende Strahlung in ein wenigstens angenähert paralleles Strahlungsbündel kollimiert. Ausserhalb dieses Strahlungsbündels ist, durch eine Blende 5 von direkter Strahlung abgeschirmt, eine weitere Kollimations-Einrichtung 6 angeordnet, deren Empfangsbereich so ausgerichtet ist, dass diese an Rauchpartiketn gestreute Strahlung aus einem Streuvolumen 7 aufnimmt und dem Eingang 8 eines zweiten Lichtleiters L2 zuführt, der die empfangene Streustrahlung einer Solarzelle 9 zuleitet. Diese Solarzelle wandelt die empfangene Strahlung, d.h. das optische Signal in ein elektrisches Signal um, das von einem Empfangsverstärker 10 verstärkt wird. Das Verstärker-Ausgangssignal wird von einer Signalverarbeitungsschaltung aufgenommen, die andererseits über eine Leitung 12 ein Referenzsignal von der Steuerschaltung 1 erhält, und die nur dann ein Signal an die nachgeschaltete Anzeigeschaltung 13 weitergibt, wenn ausgesandte und empfangene Strahlung in Koinzidenz sind. Diese Anzeigeschaltung 13 zeigt, bei Verwendung als Rauchsensor, die Rauchkonzentration entsprechend dem Wert des Streustrahlungssignales an, oder sie löst, bei Verwendung als Brandmelder, eine Alarmeinrichtung 14 aus, wenn das Streustrahlungssignal eine vorgegebene Schwelle übersteigt, und zeigt somit einen Brandausbruch an.At the output 3 of this light guide, a collimation device 4 is arranged, ie a special optic that collimates the radiation emerging from the light guide into an at least approximately parallel radiation beam. Outside this radiation beam, shielded from direct radiation by a diaphragm 5, there is a further collimation device 6 whose reception area is oriented in such a way that it receives radiation scattered on smoke particles from a scattering volume 7 and feeds the input 8 of a second light guide L 2 , which feeds the received scattered radiation from a solar cell 9. This solar cell converts the received radiation, ie the optical signal, into an electrical signal, which is amplified by a receiving amplifier 10. The amplifier output signal is received by a signal processing circuit which, on the other hand, receives a reference signal from the control circuit 1 via a line 12 and which only forwards a signal to the downstream display circuit 13 when the emitted and received radiation are in coincidence. This display circuit 13, when used as a smoke sensor, indicates the smoke concentration according to the value of the scattered radiation signal, or it triggers an alarm device 14, when used as a fire detector, if the scattered radiation signal exceeds a predetermined threshold, and thus indicates a fire outbreak.

Figur 2 zeigt den Aufbau der Detektoreinheit D eines speziell zur Brandmeldung geeigneten Streustrahlungs-Rauchdtektors. Eine Kunststoff-Basisplatte 20 trägt ein luftdurchlässiges, die Messkammer M umschliessendes Gehäuse 21 und im Inneren ein Trägerelement 22. In der Basisplatte 20 ist eine bekannte Anschluss- oder Steckverbindung C vorgesehen, die zum Anschluss der Lichtleiter L, und L2 an die Lichtleiter-Verbindungen 23 und 28 im Detektor-Inneren dient, deren Enden mit den Kollimations-Einrichtungen 24 und 26 zusammenwirken. Im zentralen Teil des Trägerelements sind mehrere Blenden 25 zur Abschirmung der Reststrahlung vom Kollimator 26 aufgesetzt. Zur Vermeidung von Störstrahlung ist die optische Anordnung im Inneren des Gehäuses 21 von einem luftdurchlässigen, aber strahlungsabsorbierenden, labyrinth-artigen Element 27 umgeben, das z.B. ineinandergeschachtelte Lamellen oder strahlungsabsorbierende Rippen 29 auf den Oberflächen aufweisen kann. Zum Auffangen der Direktstrahlung kann eine geeignete Strahlungsfalle 30 vorgesehen sein, sowie eine entsprechende Strahlungsfalle 31 zum Abschluss des Empfangsbereiches.FIG. 2 shows the construction of the detector unit D of a scattered radiation smoke detector which is particularly suitable for fire detection. A plastic base plate 20 carries an air-permeable housing 21 enclosing the measuring chamber M and a support element 22 inside. A known connection or plug connection C is provided in the base plate 20, which is used to connect the light guides L and L 2 to the light guide Connections 23 and 28 inside the detector is used, the ends of which interact with the collimation devices 24 and 26. A plurality of diaphragms 25 for shielding the residual radiation from the collimator 26 are placed in the central part of the carrier element. To avoid interference radiation, the optical arrangement in the interior of the housing 21 is surrounded by an air-permeable, but radiation-absorbing, labyrinth-like element 27, which can have nested slats or radiation-absorbing ribs 29 on the surfaces, for example. A suitable radiation trap 30 can be provided to catch the direct radiation, as well as a corresponding radiation trap 31 at the end of the reception area.

Obwohl die Erfindung speziell für solche Detektoreinheiten von Vorteil ist, bei denen die Speisung und Signalübertragung mittels Lichtleitern oder Fiber-Optik vorgenommen wird, wo meist nur eine kleine Strahlungsleistung zur Verfügung steht, erweist sie sich jedoch auch von besonderem Vorteil bei klassischen Rauchdetektoren mit elektrischer Übertragung, speziell wenn eine besonders hohe Empfindlichkeit verlangt wird, d.h. wenn geringste Rauchkonzentrationen nachgewiesen werden sollen. Bei der Anordnung nach Figur 1 tritt dabei die Strahlungsquelle 2 an die Stelle der Einrichtung 4, und der Strahlungsempfänger 9 an die Stelle der Einrichtung 6, und die Lichtleiter-Verbindungen L1 und L2 entfallen. Der konstruktive Aufbau solcher Rauchdetektoren kann dabei beispielsweise entsprechend US-A- 4 181 439 ausgeführt sein.Although the invention is particularly advantageous for those detector units in which the supply and signal transmission is carried out by means of optical fibers or fiber optics, where usually only a small radiation power is available, it also proves to be particularly advantageous in the case of classic smoke detectors with electrical transmission , especially when a particularly high sensitivity is required, ie when the lowest smoke concentrations are to be detected. In the arrangement according to FIG. 1, the radiation source 2 takes the place of the device 4, and the radiation receiver 9 takes the place of the device 6, and the light guide connections L 1 and L 2 are omitted. The construction of such smoke detectors can be carried out, for example, in accordance with US Pat. No. 4,181,439.

Figur 3 zeigt ein Beispiel einer für den Rauchdetektor nach Figur 1 und 2 geeigneten Signalverarbeitungsschaltung 11. Bei dieser wird das Ausgangssignal des Empfänger-Verstärkers und Signalwandlers 10 über einen rauscharmen Vorverstärker 15 einem Frequenzfilter 16 zugeleitet, das bevorzugt für die Frequenz der Steuerschaltung 1 durchlässig ist und das Rauschen dämpft. Vorverstärker 15 und Frequenzfilter 16 können auch zu einem frequenzselektiven Verstärker zusammengefasst sein. Das gefilterte Signal gelangt zu einer phasenempfindlichen Schaltung 17, die andererseits von der Steuerschaltung 1 über eine Triggerschaltung 32 und einen Phasenschieber 33 angesteuert wird. Diese phasenempfindliche Schaltung 17 bewirkt, dass die Polarität des vom Empfänger 10 kommenden Signals je nach Phasenlage des Wechselsignals der Steuerschaltung 1 beibehalten oder umgekehrt wird. Beispielsweise wird während der Einschaltphasen der Strahlungsquelle die Polarität beibehalten, das Empfängersignal also unverändert weitergegeben, während der dazwischenliegenden Ausschaltphasen jedoch umgekehrt, d.h. ein positives Signal in ein negatives verwandelt und umgekehrt ein negatives Signal in ein positives. Das so veränderte Ausgangssignal der phasenempfindlichen Schaltung 17 gelangt nun zu einer nachgeschalteten Integrationsschaltung 18 mit einer vorgegebenen Zeitkonstante, die einstellbar sein kann, z.B. mittels eines Kondensators 19. Die gesamte Signalverarbeitungsschaltung 11 kann auch als eine einzige Hybrid-Schaltung oder ein entsprechendes Gerät ausgeführt sein, z.B. als sogenannter Lock-In-Amplifier.FIG. 3 shows an example of a signal processing circuit 11 suitable for the smoke detector according to FIGS. 1 and 2. In this, the output signal of the receiver amplifier and signal converter 10 is fed via a low-noise preamplifier 15 to a frequency filter 16, which is preferably transparent to the frequency of the control circuit 1 and dampens the noise. Preamplifier 15 and frequency filter 16 can also be combined to form a frequency-selective amplifier. The filtered signal arrives at a phase-sensitive circuit 17, which on the other hand is controlled by the control circuit 1 via a trigger circuit 32 and a phase shifter 33. This phase-sensitive circuit 17 has the effect that the polarity of the signal coming from the receiver 10 is maintained, or vice versa, depending on the phase position of the alternating signal of the control circuit 1. For example, the polarity is maintained during the switch-on phases of the radiation source, ie the receiver signal is passed on unchanged, but vice versa during the switch-off phases in between, ie a positive signal is converted into a negative one and vice versa a negative signal is turned into a positive one. That so changed output signal of the phase-sensitive circuit 17 now arrives at a downstream integration circuit 18 with a predetermined time constant, which can be adjustable, for example by means of a capacitor 19. The entire signal processing circuit 11 can also be designed as a single hybrid circuit or a corresponding device, for example as so-called lock-in amplifier.

Bei einer praktisch ausgeführten Auswerteschaltung wurden die folgenden auf dem Markt erhältlichen Komponenten verwendet:

  • - Steuerschaltung 1: 555-Timer (Signetics) mit 7473 Flip-Flop
  • - Strahlungsquelle 2: 2 SE 3352 (Honeywell)
  • - Strahlungsempfänger 9: PIN BPX 65 (Siemens)
  • - Empfängerverstärker 10: ICL 7621 (Intersil)
  • - Signalverarbeitungsschaltung 11: 0181 (Novasina)
The following components available on the market were used in a practical evaluation circuit:
  • - Control circuit 1: 555 timer (Signetics) with 7473 flip-flop
  • - Radiation source 2: 2 SE 3352 (Honeywell)
  • - Radiation receiver 9: PIN BPX 65 (Siemens)
  • - Receiver amplifier 10: ICL 7621 (Intersil)
  • - signal processing circuit 11: 0181 (Novasina)

oder Gerät: 5206 Lock-In (EG & G)or device: 5206 Lock-In (EG & G)

Die Funktion der Schaltung wird an Hand der in Figur 4 wiedergegebenen zeitlichen Signalverläufe an verschiedenen Punkten der Signalverarbeitungsschaltung nach Figur 3 erläutert. Die phasenempfindliche Schaltung 17 erhält an ihrem Steuereingang das verstärkte Signal a der Steuerschaltung 1, wobei mit dem Phasenschieber 33 allfällige Phasenverschiebungen des Empfängersignals beim Signaldurchlauf korrigiert werden können, und an ihrem Signaleingang das verstärkte und gefilterte Empfängersignal b. Das Ausgangssignal c der phasenempfindlichen Schaltung 17 erscheint am Ausgang und wird von der Integrationsschaltung 18 zu einem Ausgangssignal d integriert. Während des Zeitabschnittes X wird keine Streustrahlung empfangen. Das Signal b ist dann ein reines Rauschsignal ohne jeden Frequenzanteil der Steuerschaltung 1. Das Signal c ist dann ebenfalls ein reines Rauschsignal, welches integriert das Signal d = 0 ergibt. Im folgenden Zeitabschmitt Y sind dem allgemeinen Rauschen zwei unregelmässige Störsignale b1 und b2 überlagert. Da diese Signale nicht synchron mit dem Steuersignal a auftreten, werden sie durch die periodische Phasenumkehr in unregelmässige Signale c verwandelt, so dass das integrierte Signal d nicht wesentlich von 0 abweicht. Ist jedoch im Zeitabschnitt Z im empfangenen Signal b auch nur ein geringer periodischer Anteil enthalten, der frequenzgleich und phasengleich mit dem Steuersignal a ist, so wird dieser Anteil, auch wenn er wesentlich schwächer als das gleichzeitig vorhandene Rauschen und in diesem kaum wahrnehmbar ist, durch die periodische Phasenumkehr in ein konstant positives Signal c verwandelt. Die Integration ergibt daher ein stetig zunehmendes Signal d. Die Anstiegsgeschwindigkeit wird dabei durch die Zeitkonstante der Integrationsschaltung 18 bestimmt und kann durch eine geeignete Wahl oder Einstellung der Zeitkonstanten an die zu erwartende Störimpulshäufigkeit angepasst werden, so dass ein bestimmter Anstieg zwar durch eine bestimmte Anzahl aufeinanderfolgender synchroner Empfängerimpulse, jedoch niemals durch unregelmässig auftretende Störimpulse erreicht wird. Sobald nun das integrierte Signal d eine vorgegebene Schwelle do überschreitet, d.h. die Alarmschwelle erreicht, so wird eine . Anzeigeschaltung 13 an sich bekannter Art angesteuert, die ein visuelles, akustisches oder elektrisches Alarmsignal auslöst.The function of the circuit is explained on the basis of the temporal signal curves shown in FIG. 4 at various points in the signal processing circuit in accordance with FIG. The phase-sensitive circuit 17 receives the amplified signal a of the control circuit 1 at its control input, with the phase shifter 33 being able to correct any phase shifts in the receiver signal during signal passage, and the amplified and filtered receiver signal b at its signal input. The output signal c of the phase-sensitive circuit 17 appears at the output and is integrated by the integration circuit 18 into an output signal d. No scattered radiation is received during the period X. The signal b is then a pure noise signal without any frequency component of the control circuit 1. The signal c is then also a pure noise signal which, when integrated, gives the signal d = 0. In the following time period Y two irregular noise signals b 1 and b 2 are superimposed on the general noise. Since these signals do not occur in synchronism with the control signal a, they are converted into irregular signals c by the periodic phase reversal, so that the integrated signal d does not deviate significantly from 0. However, if there is only a small periodic component in the received signal b in the time segment Z, which is in frequency and in phase with the control signal a, then this component, even if it is significantly weaker than the noise present at the same time and is barely perceptible in it the periodic phase inversion is converted into a constantly positive signal c. The integration therefore results in a steadily increasing signal d. The rate of increase is determined by the time constant of the integration circuit 18 and can be adapted to the expected interference frequency by a suitable choice or setting of the time constant, so that a certain increase is achieved by a certain number of successive synchronous receiver pulses, but never by irregularly occurring interference pulses becomes. As soon as the integrated signal d exceeds a predefined threshold d o , ie the alarm threshold is reached, a. Display circuit 13 controlled in a known manner, which triggers a visual, acoustic or electrical alarm signal.

Es sei bemerkt, dass sich die Schaltung vereinfachen lässt, wenn die von der Steuerschaltung 1 abgegebene Steuerspannung rechteckförmig ausgebildet ist. In diesem Falle schwankt das aus der als einfaches Frequenzfilter ausgebildeten Schaltung 32 herauskommende Wechselsignal zwischen den Extremwerten (+1) und (-1) periodisch hin und her. Die phasenempfindliche Schaltung kann dann als einfache Multiplikationsschaltung 17 ausgeführt sein, da die abwechselnde Multiplikation mit (+1) und (-1) genau die erforderliche Wirkung hat, nämlich die Polaritätsumkehr des Signales im Rhythmus des Steuersignales.It should be noted that the circuit can be simplified if the control voltage output by the control circuit 1 is rectangular. In this case, the alternating signal coming out of the circuit 32 designed as a simple frequency filter fluctuates periodically back and forth between the extreme values (+1) and (-1). The phase-sensitive circuit can then be designed as a simple multiplication circuit 17, since the alternating multiplication by (+1) and (-1) has exactly the required effect, namely the polarity reversal of the signal in the rhythm of the control signal.

Die Erfindung wurde vorstehend zwar an Hand eines Streustrahlungs-Rauchdetektors beschrieben. Der Erfindungsgedanke lässt sich analog, mit ähnlichen Vorteilen auch bei anderen Typen von photoelektrischen Rauchdetektoren, wie z.B. Strahlungsextinktions- oder photoakustischen Rauchdetektoren anwenden. Die dazu erforderlichen Anpassungsmassnahmen sind dem Fachmann geläufig. In jedem Falle kann erreicht werden, dass eine Anzeige oder ein Alarmsignal mit ausserordentlicher Sicherheit nur dann ausgelöst wird, wenn das Empfängersignal genau synchron, d.h. absolut frequenzgleich und phasengleich mit dem die Strahlungsquelle steuernden Signal ist, jedoch durch keine anderen Störsignale. Die Schaltung arbeitet auch dann noch sicher und zuverlässig, wenn das Empfängersignal äusserst schwach ist und das Rauschen das Nutzsignal völlig überdeckt, so dass geringere Rauchkonzentrationen nachgewiesen oder gemessen werden können als bisher. Dabei weicht die Erfindung bewusst von der bisherigen, dem Fachmann naheliegenden Tendenz ab, das Signal-/RauschVerhältnis dadurch zu verbessern, dass die Strahlungsimpuls-Höhe vergrössert und die Strahlungsimpuls-Breite verkleinert wird. Die erfindungsgemässe Schaltung arbeitet mit besonderem Vorteil auch in Fällen, wo es zweckmässig oder notwendig ist, die Impulsbreiten in der gleichen Grössenordnung wie die Zwischenzeiten zu wählen.The invention has been described above using a scattered radiation smoke detector. The inventive idea can be analog, with similar advantages also with other types of photoelectric smoke detectors, such as Use radiation absorbance or photoacoustic smoke detectors. The adjustment measures required for this are familiar to the person skilled in the art. In any case, it can be achieved that a display or an alarm signal with exceptional security is only triggered if the receiver signal is exactly synchronous, i.e. is absolutely the same frequency and in phase with the signal controlling the radiation source, but no other interference signals. The circuit also works safely and reliably when the receiver signal is extremely weak and the noise completely covers the useful signal, so that lower smoke concentrations can be detected or measured than before. The invention deliberately deviates from the previous tendency, which is obvious to the person skilled in the art, to improve the signal / noise ratio by increasing the radiation pulse height and reducing the radiation pulse width. The circuit according to the invention works with particular advantage even in cases where it is expedient or necessary to choose the pulse widths in the same order of magnitude as the intermediate times.

Der beschriebene Rauchdetektor dient zwar vorzugsweise als Brandmelder, ist jedoch auch für andere Verwendungen geeignet, z.B. zur Rauchgasüberwachung, Rauchdichtemessung etc.The smoke detector described preferably serves as a fire detector, but is also suitable for other uses, e.g. for smoke gas monitoring, smoke density measurement etc.

Claims (9)

1. Photoelectric smoke detector having a radiation source (2) driven intermittently by a control circuit (1) and a radiation receiver (9) connected to an evaluation circuit (A) capable of outputting a smoke alarm signal when said radiation receiver (9) receives radiation influenced by smoke particles in synchronization with the operation of said radiation source (2) which evaluation circuit (A) comprises a circuit (17) regulated by said control circuit (1) and by said radiation receiver (9), as well as an integrating circuit (18) which integrates the output signal (c) of said circuit (17) with a prescribed time-constant and regulates a display circuit (13) for the smoke alarm signal in correspondence with the integrated signal (d), characterized in that said circuit (17) is constructed in such manner as a phase sensitive circuit that the analog alternating signal (b) of the radiation receiver (9) is left unchanged when the alternating signal (a) of the control circuit (1) has the one phase relation and that the analog alternating signal (b) of the radiation receiver (9) is inverted when the alternating signal (a) of the control circuit (1) has the other phase relation.
2. Smoke detector according to patent claim 1, characterized in that the alternating signal (b) of the radiation receiver (9) is transmitted through a frequency filter (18) to the phase sensitive circuit (17).
3. Smoke detector according to patent claim 1 or 2, characterized in that the alternating signal (b) of the control circuit (1) is transmitted through a phase shift circuit (33) to the phase sensitive circuit (17).
4. Smoke detector according to any of the patent claims 1 to 3, characterized in that the time-constant of the integrating circuit (18) is variable.
5. Smoke detector according to any of the patent claims 1 to 4, characterized in that the control circuit (1) generates a periodical signal (a) for operating the radiation source (2) and for regulating the phase sensitive circuit (17), wherein the active periods of such periodical signal have the same order of magnitude as the inactive intervals.
6. Smoke detector according to any of the patent claims 1 to 5, characterized in that the control circuit (1) generates an at least approximately square-wave signal (a) whose alternating component is transmitted to the phase sensitive circuit (17).
7. Smoke detector according to the patent claim 6, characterized in that the phase sensitive circuit (17) is structured as mulitiplier circuit.
8. Smoke detector according to any of the patent claims 1 to 7, characterized in that the dicplay circuit (13) is structured to output a signal as soon as the integrated signal (d) exceeds a prescribed threshold value (do).
9. Smoke detector according to any of the patent claims 1 to 8, characterized in that the radiation receiver (9) is structured and disposed to receive radiation scattered from smoke particles and to emit a signal depending on the intensity of the received scattered radiation.
EP83902981A 1983-01-11 1983-10-05 Photoelectric smoke detector Expired EP0130992B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH119/83 1983-01-11
CH119/83A CH660244A5 (en) 1983-01-11 1983-01-11 PHOTOELECTRIC SMOKE DETECTOR AND THEIR USE.

Publications (2)

Publication Number Publication Date
EP0130992A1 EP0130992A1 (en) 1985-01-16
EP0130992B1 true EP0130992B1 (en) 1987-04-08

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US (1) US4647786A (en)
EP (1) EP0130992B1 (en)
JP (1) JPS60500467A (en)
CH (1) CH660244A5 (en)
DE (1) DE3370888D1 (en)
NO (1) NO159424C (en)
WO (1) WO1984002790A1 (en)

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US4839527A (en) * 1986-10-28 1989-06-13 Alan Leitch Optical-fibre smoke detection/analysis system
GB9014015D0 (en) * 1990-06-23 1990-08-15 Dennis Peter N J Improvements in or relating to smoke detectors
US5546074A (en) * 1993-08-19 1996-08-13 Sentrol, Inc. Smoke detector system with self-diagnostic capabilities and replaceable smoke intake canopy
US6501810B1 (en) 1998-10-13 2002-12-31 Agere Systems Inc. Fast frame synchronization
JP3330438B2 (en) * 1993-12-16 2002-09-30 能美防災株式会社 Smoke detector and its adjusting device
US5629458A (en) * 1996-07-26 1997-05-13 Alliedsignal Inc. Process for the preparation of 2 2 2 trifluoroethanol
GB2367358B (en) * 1997-06-30 2002-05-15 Hochiki Co Smoke detecting apparatus
DE19741853A1 (en) * 1997-09-23 1999-03-25 Bosch Gmbh Robert Hollow ellipse smoke alarm
US7324004B2 (en) * 2003-10-29 2008-01-29 Honeywell International, Inc. Cargo smoke detector and related method for reducing false detects
DK2093734T3 (en) * 2008-02-19 2011-10-10 Siemens Ag Smoke alarm with timely interpretation of a feedback signal, test method for operation of a smoke alarm
DE102013213721B4 (en) * 2013-03-07 2015-10-22 Siemens Schweiz Ag Fire alarm system for use in a nuclear or hazardous area
ES2948115T3 (en) * 2016-11-11 2023-08-31 Carrier Corp High sensitivity fiber optic based detection
CN115223323B (en) * 2022-07-18 2023-05-23 深圳市千宝通通科技有限公司 Photoelectric smoke sensor, smoke sensor self-checking method and smoke alarm

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NO159424B (en) 1988-09-12
CH660244A5 (en) 1987-03-31
JPH0568000B2 (en) 1993-09-28
US4647786A (en) 1987-03-03
NO159424C (en) 1988-12-21
JPS60500467A (en) 1985-04-04
WO1984002790A1 (en) 1984-07-19
DE3370888D1 (en) 1987-05-14
EP0130992A1 (en) 1985-01-16
NO842034L (en) 1984-07-19

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