EP0130992A1 - Photoelectric smoke detector. - Google Patents

Photoelectric smoke detector.

Info

Publication number
EP0130992A1
EP0130992A1 EP83902981A EP83902981A EP0130992A1 EP 0130992 A1 EP0130992 A1 EP 0130992A1 EP 83902981 A EP83902981 A EP 83902981A EP 83902981 A EP83902981 A EP 83902981A EP 0130992 A1 EP0130992 A1 EP 0130992A1
Authority
EP
European Patent Office
Prior art keywords
signal
radiation
circuit
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.)
Granted
Application number
EP83902981A
Other languages
German (de)
French (fr)
Other versions
EP0130992B1 (en
Inventor
Hannes Guttinger
Martin Labhart
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
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Cerberus AG filed Critical Cerberus AG
Publication of EP0130992A1 publication Critical patent/EP0130992A1/en
Application granted granted Critical
Publication of EP0130992B1 publication Critical patent/EP0130992B1/en
Expired legal-status Critical Current

Links

Classifications

    • 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 with a radiation source operated intermittently by a control circuit and a radiation receiver which is connected to an evaluation circuit which can emit a smoke signal when the radiation receiver is influenced by smoke particles and synchronously with the operation the radiation source receives.
  • 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 pulses when radiation pulses are absorbed, which are converted into electrical impulses by an acoustic-electrical converter, such as, for example described in European patent application EP 14 251.
  • 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, is radiated into a measurement volume , for example by means of a light-emitting diode (LED), and the radiation scattered on smoke particles in the measurement volume from outside
  • LED light-emitting diode
  • Scattered radiation receiver recorded, and a smoke alarm signal is given by an evaluation circuit when the scattered radiation level exceeds a certain threshold.
  • a crucial problem here is to ensure that a smoke alarm signal is only triggered by scattered radiation from smoke particles, but not by interference 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 in the case of smoke detectors in which only a limited radiation intensity is available in the measurement volume, for example in the case of smoke detectors in which the radiation is guided into the measurement volume and removed therefrom by means of radiation-conducting elements or fiber optics, such as e.g. described in DE patent application 30 37 636.
  • Such evaluation circuits can be used to achieve a fire alarm that is not susceptible to faults, provided that sufficient intensive radiation pulses are available.
  • radiation sources only allow a limited maximum intensity without damage or rapid aging, and radiation attenuation occurs 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 achieve sufficient scattered radiation power to get,.
  • the evaluation circuits described here no longer operate with sufficient interference immunity, on the one hand because the occurrence of interference pulses in the switch-on intervals is much more likely, and on the other hand because the signal-to-noise ratio in the radiation receiver can become so small that individual noise Pulses can reach the signal level and can trigger a faulty signal. Particularly low smoke concentrations at which the signal lies within the noise level could not be detected at all in this way, ie the sensitivity of fire detectors with such evaluation circuits was limited.
  • the invention sets itself the task of avoiding the disadvantages of the prior art mentioned and, in particular, of creating a photoelectric smoke detector which has improved interference immunity and which permits greater sensitivity to smoke even with reduced radiation intensity and power.
  • the invention is characterized in that the evaluation circuit has a phase-sensitive circuit which is controlled by the control circuit and which reverses the alternating signal of the radiation receiver depending on the phase position of the alternating signal of the control circuit, and an integration circuit which the output signal of the phase-sensitive circuit integrated with a certain time constant and controls a display circuit according to the integrated signal.
  • the evaluation circuit has a phase-sensitive circuit which is controlled by the control circuit and which reverses the alternating signal of the radiation receiver depending on the phase position of the alternating signal of the control circuit, and an integration circuit which the output signal of the phase-sensitive circuit integrated with a certain time constant and controls a display circuit according to the integrated signal.
  • FIG. 1 shows an example of a block circuit diagram of a scattered radiation smoke detector
  • FIG. 2 shows an example of the design 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.
  • a detector unit D is connected to an evaluation circuit A by means of radiation-conducting elements or light guides L ⁇ and L 2 .
  • the type of light guide is expediently adapted to the radiation used.
  • Several 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 visible light, infrared or ultraviolet radiation, depending on the type of LED, is coupled into the light guide L 1 and passed via this to the detector unit D.
  • a collimation device 4 is arranged, ie a special optic which collimates the radiation emerging from the light guide into a radiation beam which is at least approximately parallel.
  • a further collimation device 6 the reception area of which is oriented such that it receives radiation scattered by smoke particles from a scattering volume 7 and the input 8 of a second light guide L 2 supplies, 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 indicates the smoke concentration corresponding 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 shows a fire outbreak.
  • FIG. 2 shows the construction of the detector unit D of a scattered radiation raucetector 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 for connecting the light guides L and L ⁇ to the light guide connections 23 and 28 inside the detector, the ends of which cooperate with the coordination devices 24 and 26.
  • a plurality of diaphragms 25 are attached to shield the residual radiation from the collimator 26.
  • the optical arrangement in the interior of the housing 21 is surrounded by an air-permeable, but radiation-absorbing, labyrinth-like element 27, which may have nested lamellae or radiation-absorbing ribs 29 on the surfaces, for example.
  • a suitable radiation can be provided every 30 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 light guides 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 ones 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, and L 2 are omitted.
  • the construction of such smoke detectors can be carried out, for example, in accordance with US Pat.
  • 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 Slider 33 is controlled.
  • 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, that is to say 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 into a positive one.
  • the output signal of the phase-sensitive circuit 17 changed in this way 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 a single hybrid circuit or a corresponding one Device, for example as a so-called lock-in amplifier.
  • Control circuit 1 555 timer (Signetics) with 7473 flip-flop
  • the function of the circuit is shown on the basis of the temporal signal curves shown in FIG. explained at various points in the signal processing circuit according to FIG.
  • the phase-sensitive circuit 17 receives the amplified signal of the control circuit 1 at its control input a, any phase shifts of the receiver signal during signal passage can be corrected with the phase shifter 33, and the amplified and filtered receiver signal at its signal input b.
  • the exit Signal of the phase-sensitive circuit 17 appears at the output c 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 frequency of interference pulses by a suitable choice or setting of the time constant, so that a certain increase does occur through a certain number of consecutive synchronous receiver pulses , but is never achieved by irregularly occurring interference pulses.
  • a display circuit 13 of a type known per se is triggered 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 with (+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 in other types of photoelectric smoke detectors, such as Use radiation absorbance or photoacoustic smoke detectors.
  • the adaptation measures required for this are familiar to the person skilled in the art.
  • it can be achieved that an indication 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 by 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 a 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

Dans un détecteur de fumée photoélectrique, une source de rayonnement (2) est actionnée de manière intermittente par une unité de commande (1) et le rayonnement sur lequel influent des particules de fumée, par exemple le rayonnement diffusé, est capté par un radiorécepteur (9). Le signal du radiorécepteur (9) est amené à une unité de traitement des signaux (11) actionnée simultanément par l'unité de commande (1) possèdant une unité sensible aux phases qui inverse le signal reçu selon la position de phase du signal de l'unité de commande (1) et qui amène le signal ainsi modifié à une unité d'intégration dont le signal de sortie intégré actionne une unité d'affichage (13); ce dernier peut par exemple émettre un signal d'alarme lorsque le signal intégré, c'est-à-dire la densité de fumée, dépasse une valeur seuil prédéterminée, ou alors afficher la densité de fumée. Ainsi de faibles signaux de fumée peuvent aussi être décelés d'une manière sûre et fiable, même lorsqu'ils sont entièrement couverts par le bruit de fond. Un tel détecteur de fumée peut être utilisé avantageusement comme avertisseur d'incendie sensible et fiable.In a photoelectric smoke detector, a radiation source (2) is actuated intermittently by a control unit (1) and the radiation on which smoke particles influence, for example scattered radiation, is picked up by a radio receiver ( 9). The signal from the radio receiver (9) is supplied to a signal processing unit (11) actuated simultaneously by the control unit (1) having a phase-sensitive unit which reverses the received signal according to the phase position of the signal of the 'control unit (1) and which brings the signal thus modified to an integration unit whose integrated output signal actuates a display unit (13); the latter can for example emit an alarm signal when the integrated signal, that is to say the smoke density, exceeds a predetermined threshold value, or else display the smoke density. Thus weak smoke signals can also be detected in a safe and reliable manner, even when they are completely covered by the background noise. Such a smoke detector can advantageously be used as a sensitive and reliable fire alarm.

Description

Photoelektrischer Rauchdetektor und dessen Verwendung Photoelectric smoke detector and its use
Die Erfindung betrifft einen photoelektrischen Rauchdetek¬ tor mit einer von einer Steuerschaltung intermittierend betriebenen Strahlungsquelle und einem Strahlungsempfän¬ ger, der mit einer Auswerteschaltung verbunden ist, die ein Rauchsignal abzugeben vermag, wenn der Strahlungsem¬ pfänger durch Rauchpartikel beeinflusste Strahlung syn¬ chron mit dem Betrieb der Strahlungsquelle empfängt.The invention relates to a photoelectric smoke detector with a radiation source operated intermittently by a control circuit and a radiation receiver which is connected to an evaluation circuit which can emit a smoke signal when the radiation receiver is influenced by smoke particles and synchronously with the operation the radiation source receives.
Der Rauchdetektor kann dabei z.B. als Streustrahlungs¬ detektor ausgebildet sein, bei dem die an Rauchpartikeln gestreute Strahlung ausgewertet wird, oder als Strahlungs- extinktionsdetektor, 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 europäischen Patentanmeldung EP 14 251 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 pulses when radiation pulses are absorbed, which are converted into electrical impulses by an acoustic-electrical converter, such as, for example described in European patent application EP 14 251. 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-An eldung 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 ausserhalbIn 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 , for example by means of a light-emitting diode (LED), and the radiation scattered on smoke particles in the measurement volume from outside
As ( OOMMPPII _ des Strahlungsbereiches der Strahlungsquelle angeordnetenA s (OOMMPPII _ the radiation area of the radiation source
Streustrahlungsempfänger aufgenommen, und mittels einer Auswerteschaltung wird ein Rauchalarmsignal gegeben, wenn das Streustrahlungsniveau eine bestimmte Schwelle übersteigt.Scattered radiation receiver recorded, and a smoke alarm signal is given by an evaluation circuit when the scattered 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 Strahlungs-Intensität im Messvolumen zur Ver¬ fügung steht, beispielsweise bei Rauchdetektoren, bei denen die Strahlung mittels strahlungsleitender Elemente oder Fiber-Optik in das Messvolumen geleitet und daraus abge¬ nommen wird, wie z.B. in der DE-Patentanmeldung 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 interference 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 in the case of smoke detectors in which only a limited radiation intensity is available in the measurement volume, for example in the case of smoke detectors in which the radiation is guided into the measurement volume and removed therefrom by means of radiation-conducting elements or fiber optics, such as e.g. described in DE patent application 30 37 636.
Um eine falsche Rauchsignalgabe durch Störstrahlung zu verhindern, ist es bereits bekannt, z.B. aus den europä¬ ischen Patenten EP 11 205 oder EP 14 779, die Strahlungs¬ quelle nur in sehr kurzzeitigen Impulsen zu betreiben und den Strahlungsempfänger an eine Koinzidenzschaltung an2u- schliessen, die nur dann ein Rauchsignal erzeugt, wenn Streustrahlung während der kurzzeitigen Strahlungsimpulse -empfangen wird, jedoch nicht bei Auftreten von Störstrah¬ lungsimpulsen in den Zwischenzeiten. Der seltene Fall, dass ein Störimpuls in der kurzen Zeit eines Strahlungsimpulses eintrifft, kann dabei durch eine Repetierschaltung elimi¬ niert werden, die nur dann ein Rauchsignal weitergibt, wenn mehrere Koinzidenzen hintereinander auftreten.In order to prevent false smoke signaling by interference radiation, it is already known, e.g. from European patents EP 11 205 or EP 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 scatter radiation is received during the short-term radiation pulses is, 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 which only passes on a smoke signal if several coincidences occur in succession.
Mit derartigen Auswerteschaltungen lässt sich eine störun- anfällige Brandmeldung erreichen, sofern ausreichend inten¬ sive Strahlungsimpulse zur Verfügung stehen. Viele Strah- lungsquellen lassen jedoch nur eine beschränkte Maximal¬ intensität ohne Schädigung oder schnelle Alterung zu, und bei Fiberoptik-Uebertragung erfolgt eine Strahlungsdämpfung, so dass es zweckmässig oder notwendig ist, längere Ein¬ schaltzeiten der Strahlungsquelle zu wählen, um eine ge¬ nügende Streustrahlungs-Leistung zu bekommen,. Die beschrie¬ benen Auswerteschaltungen arbeiten hier nicht mehr aus¬ reichend störsicher, einerseits da das Auftreten von Stör¬ impulsen 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 fehler¬ haftes Signal auslösen können. Besonders geringe Rauch¬ konzentrationen, bei denen das Signal innerhalb des Rausch¬ pegels liegt, konnten auf diese Weise überhaupt nicht de- tektiert werden, d.h. die Empfindlichkeit von Brandmeldern mit solchen Auswerteschaltungen war begrenzt.Such evaluation circuits can be used to achieve a fire alarm that is not susceptible to faults, provided that sufficient intensive radiation pulses are available. Many rays However, radiation sources only allow a limited maximum intensity without damage or rapid aging, and radiation attenuation occurs 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 achieve sufficient scattered radiation power to get,. The evaluation circuits described here no longer operate with sufficient interference immunity, on the one hand because the occurrence of interference pulses in the switch-on intervals is much more likely, and on the other hand because the signal-to-noise ratio in the radiation receiver can become so small that individual noise Pulses can reach the signal level and can trigger a faulty signal. Particularly low smoke concentrations at which the signal lies within the noise level could not be detected at all in this way, ie the sensitivity of fire detectors with such evaluation circuits was limited.
Die Erfindung setzt sich die Aufgabe, die erwähnten Nach¬ teile des Standes der Technik zu vermeiden, und insbesonde¬ re einen photoelektrischen Rauchdetektor zu schaffen, der eine verbesserte Störsicherheit aufweist und der eine grössere Rauchempfindlichkeit auch bei verminderter Strahlungsintensität und Leistung zulässt.The invention sets itself the task of avoiding the disadvantages of the prior art mentioned and, in particular, of creating a photoelectric smoke detector which has improved interference immunity and which permits greater sensitivity to smoke even with reduced radiation intensity and power.
Die Erfindung ist dadurch gekennzeichnet, dass die Aus¬ werteschaltung eine phasenempfindliche Schaltung aufweist, die von der SteuerSchaltung gesteuert wird und die das Wechselsignal des Strahlungsempfängers je nach der Phasen¬ lage des Wechselsignales der Steuerschaltung umkehrt, sowie eine Integrationsschaltung, die das Ausgangssignal der phasenempfindlichen Schaltung mit einer bestimmten Zeit¬ konstante integriert und eine Anzeigeschaltung entsprechend dem integrierten Signal ansteuert. Die Erfindung sowie zweckmässige und vorteilhafte Weiter¬ bildungen derselben werden an Hand der in den Figuren wiedergegebenen Ausführungsbeispiele und Diagramme erläutert.The invention is characterized in that the evaluation circuit has a phase-sensitive circuit which is controlled by the control circuit and which reverses the alternating signal of the radiation receiver depending on the phase position of the alternating signal of the control circuit, and an integration circuit which the output signal of the phase-sensitive circuit integrated with a certain time constant and controls a display circuit according to the integrated signal. The invention and the expedient and advantageous further developments thereof are explained on the basis of the exemplary embodiments and diagrams shown in the figures.
Figur 1 zeigt ein Beispiel eines Blockschaltschemas eines Streustrahlungs-Rauchdetektors,FIG. 1 shows an example of a block circuit diagram of a scattered radiation smoke detector,
Figur 2 zeigt ein Beispiel für den konstruktiven Aufbau eines Streustrahlungs-Rauchdetektors,FIG. 2 shows an example of the design of a stray radiation smoke detector,
Figur 3 zeigt eine für die Rauchdetektoren nach Figur 1 und 2 geeignete Signalverarbeitungsschaltung, undFIG. 3 shows a signal processing circuit suitable for the smoke detectors according to FIGS. 1 and 2, and
Figur 4 zeigt den zeitlichen Verlauf der an verschiedenen Punkten der Signalverarbeitungsschaltung nach Figur 3 auftretenden Signale.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 Detektor¬ einheit D mittels strahlungsleitender Elemente oder Licht¬ leiter Lη 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 bekann¬ te Verzweigungselemente oder mittels verschiedener Licht¬ leiter 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 Strahlungs- quelle 2 intermittierend an, beispielsweise mit einer Frequenz von 0.1 - 40 kHz. Die Einschaltzeit liegt dabei vorzugsweise in der gleichen Grössenordnung wie die Aus¬ schaltzeit. 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 connected to an evaluation circuit A by means of radiation-conducting elements or light guides Lη and L 2 . The type of light guide is expediently adapted to the radiation used. Several 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, visible light, infrared or ultraviolet radiation, depending on the type of LED, is coupled into the light guide L 1 and passed via this to the detector unit D.
OMPI■ 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 wenig¬ stens angenähert paralleles Strahlungsbündel kollimiert. Ausserhalb dieses Strahlungsbündels ist, durch eine Blende 5 von direkter Strahlung abgeschirmt, eine weitere Kollima- tions-Einrichtung 6 angeordnet, deren Empfangsbereich so ausgerichtet ist, dass diese an Rauchpartikeln gestreute Strahlung aus einem Streuvolumen 7 aufnimmt und dem Ein¬ gang 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 ent¬ sprechend dem Wert des Streustrahlungssignales an, oder sie löst, bei Verwendung als Brandmelder, eine Alarmein¬ richtung 14 aus, wenn das Streustrahlungssignal eine vor¬ gegebene Schwelle übersteigt,und zeigt somit einen Brand¬ ausbruch an.OMPI ■ At the output 3 of this light guide, a collimation device 4 is arranged, ie a special optic which collimates the radiation emerging from the light guide into a radiation beam which is at least approximately parallel. Outside this radiation beam, shielded from direct radiation by a diaphragm 5, there is a further collimation device 6, the reception area of which is oriented such that it receives radiation scattered by smoke particles from a scattering volume 7 and the input 8 of a second light guide L 2 supplies, 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. When used as a smoke sensor, this display circuit 13 indicates the smoke concentration corresponding 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 shows a fire outbreak.
Figur 2 zeigt den Aufbau der Detektoreinheit D eines spe¬ ziell zur Brandmeldung geeigneten Streustrahlungs-Rauc - dtektors. Eine Kunststoff-Basisplatte 20 trägt ein luft¬ durchlässiges, die Messkammer M umschliessendes Gehäuse 21 und im Inneren ein Trägerelement 22. In der Basisplatte 20 ist eine bekannte .Anschluss- oder Steckverbindung C vorge¬ sehen, die zum Anschluss der Lichtleiter L, und L~ an die Lichtleiter-Verbindungen 23 und 28 im Detektor-Inneren dient, deren Enden mit den Ko11imations-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 Störstrah¬ lung ist die optische Anordnung im Inneren des Gehäuses 21 von einem luftdurchlässigen, aber Strahlungsabsorbierenden, labyrinth-artigen Element 27 umgeben, das z.B. ineinander¬ geschachtelte Lamellen oder strahlungsabsorbierende Rippen 29 auf den Oberflächen aufweisen kann. Zum Auffangen der Direktstrahlung kann eine geeignete Strahlungs alle 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 raucetector 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 for connecting the light guides L and L ~ to the light guide connections 23 and 28 inside the detector, the ends of which cooperate with the coordination devices 24 and 26. In the central part of the support element a plurality of diaphragms 25 are attached to shield the residual radiation from the collimator 26. 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 may have nested lamellae or radiation-absorbing ribs 29 on the surfaces, for example. A suitable radiation can be provided every 30 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 Signalübertra¬ gung 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 Uebertra- gung, 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 Ein¬ richtung 4, und der Strahlungsempfänger 9 an die Stelle der Einrichtung 6, und die Lichtleiter-Verbindungen L, und L2 entfallen. Der konstruktive Aufbau solcher Rauchdetektoren - kann dabei beispielsweise entsprechend US-Patent 4181439 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 light guides 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 ones 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, and L 2 are omitted. The construction of such smoke detectors can be carried out, for example, in accordance with US Pat.
Figur 3 zeigt ein Beispiel einer für den Rauchdetektor nach Figur 1 und 2 geeigneten Signalverarbeitungsschaltung 11. Bei dieser wird das Ausgangssignal des Empfänger-Verstärker 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 zusammen gefasst sein. Das gefilterte Signal gelangt zu einer phasen empfindlichen Schaltung 17, die andererseits von der Steuer schaltung 1 über eine TriggerSchaltung 32 und einen Phasen- Schieber 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 Strah¬ lungsquelle die Polarität beibehalten, das Empfängersignal also unverändert weitergegeben, während der dazwischen¬ liegenden Ausschaltphasen jedoch umgekehrt, d.h. ein positi ves Signal in ein negatives verwandelt und umgekehrt ein negatives Signal in ein positives. Das so veränderte Aus¬ gangssignal 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 Signalver¬ arbeitungsschaltung 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 case, 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 Slider 33 is controlled. 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, that is to say 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 into a positive one. The output signal of the phase-sensitive circuit 17 changed in this way 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 a single hybrid circuit or a corresponding one Device, for example as a so-called lock-in amplifier.
Bei einer praktisch ausgeführten Auswerteschaltung wurden die folgenden auf dem Markt erhältlichen Komponenten ver¬ wendet:The following components available on the market were used in a practical evaluation circuit:
- Steuerschaltung 1: 555-Timer (Signetics) mit 7473 Flip-Flop- Control circuit 1: 555 timer (Signetics) with 7473 flip-flop
- Strahlungsquelle 2: 2 SΞ 3352 (Honeywell)- Radiation source 2: 2 SΞ 3352 (Honeywell)
- Strahlungsempfänger 9: PIN BPX 65 (Siemens)- Radiation receiver 9: PIN BPX 65 (Siemens)
- Empfängerverstärker 10: ICL 7621 (Intersil)- Receiver amplifier 10: ICL 7621 (Intersil)
- Signalverarbeitungsschaltung 11: 0181 (Novasina) oder Gerät : 5206 Lock-In (EG & G)- Signal processing circuit 11: 0181 (Novasina) 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 a das verstärkte Signal der Steuer¬ schaltung 1, wobei mit dem Phasenschieber 33 allfällige Phasenverschiebungen des Empfängersignals beim Signaldurch¬ lauf korrigiert werden können, und an ihrem Signaleingang b das verstärkte und gefilterte Ξmpfängersignal. Das Ausgangs- signal der phasenempfindlichen Schaltung 17 erscheint am Ausgang c und wird von der Integrationsschaltung 18 zu einem Ausgangssignal d integriert. Während des Zeitab¬ schnittes X wird keine Streustrahlung empfangen. Das Sig¬ nal b ist dann ein reines Rauschsignal ohne jeden Frequenz¬ anteil der Steuerschaltung 1. Das Signal c ist dann eben¬ falls ein reines Rauschsignal, welches integriert das Signal d = 0 ergibt. Im folgenden Zeitabschnitt Y sind dem allgemeinen Rauschen zwei unregelmässige Störsignale bn und b2 überlagert. Da diese Signale nicht synchron mit dem Steuersignal a auftreten, werden sie durch die periodi¬ sche 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 schwä¬ cher 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 Anstiegs¬ geschwindigkeit wird dabei durch die Zeitkonstante der In¬ tegrationsschaltung 18 bestimmt und kann durch eine geeig¬ nete Wahl oder Einstellung der Zeitkonstanten an die zu erwartende Störimpulshäufigkeit angepasst werden, so dass ein bestimmter Anstieg zwar durch eine bestimmte Anzahl auf¬ einanderfolgender synchroner Empfängerimpulse, jedoch nie¬ mals durch unregelmässig auftretende Störimpulse erreicht wird. Sobald nun das integrierte Signal d eine vorgegebene Schwelle d überschreitet, d.h. die Alarmschwelle erreicht, so wird eine Anzeigeschaltung 13 an sich bekannter Art an¬ gesteuert, die ein visuelles, akustisches oder elektrisches Alarmsignal auslöst.The function of the circuit is shown on the basis of the temporal signal curves shown in FIG. explained at various points in the signal processing circuit according to FIG. The phase-sensitive circuit 17 receives the amplified signal of the control circuit 1 at its control input a, any phase shifts of the receiver signal during signal passage can be corrected with the phase shifter 33, and the amplified and filtered receiver signal at its signal input b. The exit Signal of the phase-sensitive circuit 17 appears at the output c 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 interference signals bn 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. If, however, only a small periodic component is contained in the received signal b in the time segment Z, which component is in frequency and in phase with the control signal a, then this component becomes, even if it is significantly weaker than the noise which is present at the same time and is barely perceptible in it , transformed into a constant positive signal c by the periodic phase reversal. The integration therefore results in a constantly 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 frequency of interference pulses by a suitable choice or setting of the time constant, so that a certain increase does occur through a certain number of consecutive synchronous receiver pulses , but is never achieved by irregularly occurring interference pulses. As soon as the integrated signal d exceeds a predetermined threshold d, that is to say reaches the alarm threshold, a display circuit 13 of a type known per se is triggered 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 Steuerspan¬ nung rechteckförmig ausgebildet ist. In diesem Falle schwankt das aus der als einfaches Frequenzfilter ausge¬ bildeten 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 ab¬ wechselnde Multiplikation mit (+1) und (-1) genau die er¬ forderliche 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 with (+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 Streu- strahlungs-Rauchdetektors beschrieben. Der Erfindungs¬ gedanke lässt sich analog, mit ähnlichen Vorteilen auch bei anderen Typen von photoelektrischen Rauchdetektoren, wie z.B. Strahlungsextinktions- oder photoakustischen Rauchdetektoren anwenden. Die dazu erforderlichen Anpas¬ sungsmassnahmen sind dem Fachmann geläufig. In jedem Falle kann erreicht werden, dass eine Anzeige oder ein Alarm¬ signal mit ausserordentlicher Sicherheit nur dann ausge¬ löst wird, wenn das Empfängersignal genau synchron, d.h. absolut frequenzgleich und phasengleich mit dem die Strah¬ lungsquelle 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 über¬ deckt, so dass geringere Rauchkonzentrationen nachgewiesen oder gemessen werden können als bisher. Dabei weicht die Erfindung bewusst von der bisherigen, dem Fachmann nahe¬ liegenden Tendenz ab, das Signal-/Rausch-Verhältnis dadurch zu verbessern, dass die Strahlungsimpuls-Höhe vergrössert und die Strahlungsimpuls-Breite verkleinert wird. Die erfindungsgemässe Schaltung arbeitet mit besonderem Vor¬ teil 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 in other types of photoelectric smoke detectors, such as Use radiation absorbance or photoacoustic smoke detectors. The adaptation measures required for this are familiar to the person skilled in the art. In any case, it can be achieved that an indication 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 by 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 a 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 geeig¬ net, 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.
( OMPI (OMPI

Claims

Patentansprüche Claims
1. Photoelektrischer Rauchdetektor mit einer von einer Steuerschaltung (1) intermittierend betriebenen Strahlungs¬ quelle (2) und einem Strahlungsempfänger (9), der mit einer Auswerteschaltung (A) verbunden ist, die ein Rauchsignal abzugeben vermag, wenn der Strahlungsempfänger (9) durch Rauchpartikel beeinflusste Strahlung synchron mit dem Betrieb der Strahlungsquelle (2) empfängt, dadurch gekenn¬ zeichnet, dass die Auswerteschaltung (A) eine phasene'mpfind- liche Schaltung (17) aufweist, die von der Steuerschaltung (1) gesteuert wird und die das Wechselsignal (b) des Strahlungsempfängers (9) je nach der Phasenlage des Wechselsignales (a) der Steuerschaltung (1) umkehrt, sowie eine IntegrationsSchaltung (18) , die das Ausgangssignal (c) der phasenempfindlichen Schaltung (17) mit einer bestimmten Zeitkonstante integriert und eine Anzeigeschaltung (13) entsprechend dem integrierten Signal (d) ansteuert.1. Photoelectric smoke detector with a radiation source (2) operated intermittently by a control circuit (1) and a radiation receiver (9) which is connected to an evaluation circuit (A) which can emit a smoke signal when the radiation receiver (9) passes through smoke particles influenced radiation in synchronism with the operation of the radiation source (2) receives, gekenn¬ thereby characterized, that the evaluation circuit (a) a phasene 'mpfind- Liche circuit (17) which is controlled by the control circuit (1) and the alternating signal the (b) the radiation receiver (9) depending on the phase position of the alternating signal (a) of the control circuit (1) reverses, and an integration circuit (18) which integrates the output signal (c) of the phase-sensitive circuit (17) with a certain time constant and one Display circuit (13) driven according to the integrated signal (d).
2. Rauchdetektor nach Anspruch 1, dadurch gekennzeichnet, dass das Signal des Strahlungsempfängers (9) der phasen- empfindiichen Schaltung (17) über ein Frequenzfilter (16) zugeführt wird.2. Smoke detector according to claim 1, characterized in that the signal of the radiation receiver (9) of the phase-sensitive circuit (17) is fed via a frequency filter (16).
3. Rauchdetektor nach Anspruch 1 oder 2, dadurch gekenn¬ zeichnet, dass das Signal der Steuerschaltung (1) der phasenempfindlichen Schaltung (17) über einen Phasenschiebe3. Smoke detector according to claim 1 or 2, characterized gekenn¬ characterized in that the signal of the control circuit (1) of the phase-sensitive circuit (17) via a phase shift
(33) zugeführt wird.(33) is supplied.
4.' Rauchdetektor nach einem der Ansprüche 1 - 3, dadurch gekennzeichnet, dass die Zeitkonstante der Integrations¬ schaltung (18) veränderbar ist.4. ' Smoke detector according to one of claims 1-3, characterized in that the time constant of the integration circuit (18) is variable.
OMPI OMPI
5. Rauchdetektor nach einem der Ansprüche 1 - 4, dadurch gekennzeichnet, dass die Steuerschaltung (1) zum. Betrieb der Strahlungsquelle (2) und zum Ansteuern der phasenempfind¬ lichen Schaltung (17) ein periodisches Signal (a) erzeugt, bei dem die Einschaltzeiten in der gleichen Grδssenordnung liegen wie die Zwischenzeiten.5. Smoke detector according to one of claims 1-4, characterized in that the control circuit (1) for. Operation of the radiation source (2) and for controlling the phase-sensitive circuit (17) generates a periodic signal (a), in which the switch-on times are in the same order of magnitude as the intermediate times.
6. Rauchdetektor nach einem der Ansprüche 1 - 5, dadurch gekennzeichnet, dass die SteuerSchaltung (1) ein wenigstens angenähert rechteckförmiges Signal (a) erzeugt, dessen Wechselanteil der phasenempfindlichen Schaltung (17) zuge¬ führt wird.6. Smoke detector according to one of claims 1-5, characterized in that the control circuit (1) generates an at least approximately rectangular signal (a), the alternating component of which is fed to the phase-sensitive circuit (17).
7. Rauchdetektor nach Anspruch 6, dadurch gekennzeichnet, dass die phasenempfindliche Schaltung (17) als Multiplika¬ tionsschaltung ausgebildet ist.7. Smoke detector according to claim 6, characterized in that the phase-sensitive circuit (17) is designed as a multiplication circuit.
8. Rauchdetektor nach einem der Ansprüche 1 - 7, dadurch gekennzeichnet, dass die AnzeigeSchaltung (13) ausgebildet ist, ein Signal auszulösen, sobald das integrierte Signal (d) einen vorgegebenen Schwellenwert (d ) überschreitet.8. Smoke detector according to one of claims 1-7, characterized in that the display circuit (13) is designed to trigger a signal as soon as the integrated signal (d) exceeds a predetermined threshold value (d).
9. Rauchdetektor nach einem der Ansprüche 1 - 8, dadurch gekennzeichnet, dass der Strahlungsempfänger (9) ausgebildet und angeordnet ist, an Rauchpartikeln gestreute Strahlung zu empfangen und ein Signal in Abhängigkeit von der Inten¬ sität der empfangenen Streustrahlung abzugeben.9. Smoke detector according to one of claims 1-8, characterized in that the radiation receiver (9) is designed and arranged to receive radiation scattered by smoke particles and to emit a signal depending on the intensity of the scattered radiation received.
10. Verwendung des Rauchdetektors nach einem der Ansprüche 1 - 9 zur Brandmeldung, wobei die bei einem Brand entstehen¬ den Rauchpartikel detektiert werden. 10. Use of the smoke detector according to one of claims 1-9 for fire detection, the smoke particles arising in a fire being detected.
EP83902981A 1983-01-11 1983-10-05 Photoelectric smoke detector Expired EP0130992B1 (en)

Applications Claiming Priority (2)

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

Publications (2)

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

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ID=4179681

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83902981A Expired EP0130992B1 (en) 1983-01-11 1983-10-05 Photoelectric smoke detector

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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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Also Published As

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CH660244A5 (en) 1987-03-31
NO159424B (en) 1988-09-12
NO842034L (en) 1984-07-19
JPS60500467A (en) 1985-04-04
NO159424C (en) 1988-12-21
US4647786A (en) 1987-03-03
JPH0568000B2 (en) 1993-09-28
EP0130992B1 (en) 1987-04-08
WO1984002790A1 (en) 1984-07-19
DE3370888D1 (en) 1987-05-14

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