EP1619640A1 - Streulichtrauchmelder - Google Patents

Streulichtrauchmelder Download PDF

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Publication number
EP1619640A1
EP1619640A1 EP04017433A EP04017433A EP1619640A1 EP 1619640 A1 EP1619640 A1 EP 1619640A1 EP 04017433 A EP04017433 A EP 04017433A EP 04017433 A EP04017433 A EP 04017433A EP 1619640 A1 EP1619640 A1 EP 1619640A1
Authority
EP
European Patent Office
Prior art keywords
scattered
signal
detector according
value
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.)
Withdrawn
Application number
EP04017433A
Other languages
English (en)
French (fr)
Inventor
Horst Dr. Dittrich
Kurt Dr. Hess
Max Schlegel
Catherine Vermeersch
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.)
Siemens Schweiz AG
Original Assignee
Siemens Schweiz 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 Siemens Schweiz AG filed Critical Siemens Schweiz AG
Priority to EP04017433A priority Critical patent/EP1619640A1/de
Publication of EP1619640A1 publication Critical patent/EP1619640A1/de
Withdrawn legal-status Critical Current

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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
    • G08B29/20—Calibration, including self-calibrating arrangements
    • G08B29/24—Self-calibration, e.g. compensating for environmental drift or ageing of components
    • 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

Definitions

  • the present invention relates to a scattered-light smoke detector with an optoelectronic arrangement for measuring scatter signals at a forward and a backward scatter angle, and with evaluation electronics for determining a measuring value and comparing it with an alarm threshold.
  • the object of the present invention is to increase the safety from false alarms of the scattered-light smoke detectors of the initially stated type, at the same time assuring a response that is as rapid as possible.
  • the weighting of the alarm threshold has the advantage that the type of fire is taken into account, and thereby the response is set optimally and late alarms are avoided. Moreover false alarms are reduced.
  • a first preferred embodiment of the scattered-light smoke detector according to the invention is characterized in that the weighting of the alarm threshold occurs in dependence on the relation of the scatter signals.
  • the weighting factor is selectable in an application-specific manner and is selected in dependence on a set of the setting parameters of the detector which fulfils the requirements of the customer.
  • a second preferred embodiment of the scattered-light smoke detector according to the invention is characterized in that the preprocessing of the scatter signals includes a compensation of a so-called offset signal, which is formed by the output signal of the photodiode of the optoelectronic arrangement when not receiving scattered light.
  • a third preferred embodiment is characterized in that the preprocessing of the scatter signals includes a temperature compensation performed following the compensation of the offset signal.
  • a fourth preferred embodiment is characterized by at least one temperature sensor for measuring the ambient temperature of the detector, the signals of the at least one temperature sensor being supplied to the signal preprocessing.
  • Two temperature sensors symmetrically disposed in or on the housing of the detector, are preferably provided, from the signals of which a temperature signal is obtained.
  • a fifth preferred embodiment of the scattered-light smoke detector according to the invention is characterized in that the signals of the temperature sensors are supplied to a temperature preprocessing, at the output of which the said temperature signal is provided.
  • a temperature value is preferably obtained from the temperature signal through analysis of the temperature and/or of the temperature increase.
  • a further preferred embodiment is characterized in that a determination of the short-time and long-time variance of the smoke signals is performed immediately after the preprocessing of the scatter signals, a large value of the variance being interpreted as an indication of interference.
  • the determination of the variance is performed in a filter, which selects the median value from several consecutive values of the smoke signals, and selects the middle value in respect of the time sequence, and forms the difference from these two values, this difference being proportional to the fluctuations of the smoke signals.
  • the smoke detector 1 represented in Figure 1 termed a detector in the following, includes two sensor systems, these being an optoelectronic system with two infrared-emitting light sources (IRED) 2 and 3 and a photodiode 4, and a thermal sensor system with two temperature sensors 5 and 6, consisting of NTC thermistors, for measuring the temperature in the environment of the detector 1.
  • a measurement chamber 7 is formed between the light sources 2, 3 and the photodiode 4.
  • the two sensor systems are disposed in a rotationally symmetrical housing (not shown), which is fixed in a socket mounted on the ceiling of a space to be monitored.
  • the temperature sensors 5 and 6 are disposed radially opposite one to the other, this having the advantage that they have a different behaviour of response to air flowing towards them from a given direction, so that the directional dependence of the response behaviour is reduced.
  • the arrangement of the two light sources 2 and 3 is selected so that the optical axis of the photodiode 4 encloses an obtuse angle with the optical axis of the one light source, being the light source 2 according to the figure, and encloses an acute angle with the optical axis of the other light source, being the light source 3 according to the figure.
  • the light of the light sources 2 and 3 is scattered by smoke entering the measurement chamber 7, and a portion of this scattered light falls on to the photodiode 4, the term forward scatter being used in the case of an obtuse angle between the optical axes of the light source and the photodiode, and the term backward scatter being used in the case of an acute angle between the said optical axes.
  • the mechanical structure of the detector 1 does not constitute subject-matter of the present application, and is therefore not described more fully here; reference is made, in this connection, to EP-A-1 376 505 and to the literature references cited in this application.
  • active or passive polarizing filters can be provided in the beam path on the transmitter and/or receiver side.
  • diodes which emit radiation in the visible-light wavelength range may be used as light sources 2 and 3 or, alternatively, the light sources may emit radiation of different wavelengths, for example, the one light source emitting red light and the other blue light.
  • the detector 1 performs a measurement, for example, every 2 seconds, the forward and backward scattered-light signals being generated sequentially.
  • the signals of the photodiode termed sensor signals in the following, have removed from them, in a filter 8, the coarsest interference of a defined frequency range, and then pass into an ASIC 9 which comprises, in essence, an amplifier 10 and an A/D converter 11.
  • an offset signal OF is also supplied to the sensor control software.
  • This offset signal is the output signal of the photodiode 4 when the latter does not receive scattered light from one of the two light sources 2 or 3.
  • the signals, termed T 1 and T 2 of the two temperature sensors 5 and 6 are likewise supplied to the microcontroller 12 and, following digitization in an A/D converter 18, pass to the sensor control software 13.
  • the fluctuations of the offset signal OF are smoothed in that the increase or the decrease of the sensor signals is limited to a predetermined value.
  • the offset signal OF is then subtracted from the scatter signals.
  • the preprocessing of the signals T 1 and T 2 in the temperature preprocessing 15 is necessary because there is a difference between the measured and the actual temperature that is determined by, inter alia, the thermal mass of the NTC thermistors 5 and 6 and of the detector housing, the position of the NTC thermistors in the detector 1, and influences of the detector and its environment that result in a delay.
  • the measured temperature is compared with a reference value, and the actual temperature is then back-calculated with the use of a model. This actual temperature is linearized and limited in respect of its rise, so that there is provided, at the output of the temperature preprocessing 15, a temperature signal T which, inter alia, is supplied to the smoke preprocessing 14.
  • a temperature compensation is performed, in which a correction factor, by which the scatter signals SB, SF are multiplied, is obtained from the temperature signal T. If the detector 1 is a purely optical detector without temperature sensors 5 and 6, a single temperature sensor, which supplies a temperature signal, is provided in the detector.
  • the temperature signal T passes into a temperature difference stage, denoted by the reference 16, and into a maximum temperature stage, denoted by the reference 17.
  • a temperature difference stage denoted by the reference 16
  • a maximum temperature stage denoted by the reference 17.
  • analysis is performed to determine whether the maximum of the temperature signal T exceeds an alarm value of, for example, 80°C (60°C in some countries).
  • the temperature difference stage 16 examines how rapidly the temperature signal T rises.
  • the output of the stage 16 is connected to an input of the stage 17, at the output of which is provided a temperature value T' which is used for the further signal processing.
  • the scatter signals preprocessed in the stage 14 pass into a median filter 19, which selects the median value from several, preferably five, consecutive values of the sensor signals.
  • the median filter 19 also includes a so-called time shifter which, from the said five sensor signals, selects the middle value in respect of the time sequence, i.e., the third value. From these two values is then formed the difference, which is proportional to the fluctuations of the scatter signals and renders possible an estimation of the standard deviation of the scatter signals. This, in turn, enables interference to be calculated.
  • the reference BW denotes the backward smoke signal
  • the reference FW denotes the forward smoke signal.
  • a background compensation is performed, through a very slow filtering, in which interference, resulting essentially from dust, is compensated.
  • the sum (BW + FW) of the smoke signals hereinafter called measurement value S, and the relation of the smoke signals (quotient) BW/FW, hereinafter indicated with the reference number Q, are formed; the relation Q is raised to a higher power by an exponent C.
  • the exponent C which is normally between 0 and 2, depends on the intended application and on the intended installation site of the detector 1, or, in other words, on which type of fire, in particular, whether smouldering or open fire, is to be detected as a priority.
  • Each detector 1 has a set of appropriate parameters, i.e., the so-called parameter set, which are adapted to the environment of its installation site and to the wishes of the customer.
  • the parameter set is dependent on, for example, the critical fire size, the fire risk, the risk to persons, the value concentration, the space geometry and on deceiving quantities, possible deceiving quantities being, for example, smoke not originating from a fire, exhaust gases, vapour, dust, fibres or electromagnetic interference.
  • Also performed in the extraction stage 20 is an optimization of the operating range of the A/D converter 11 (Fig. 1), and a determination of the short-time and long-time variance of the sensor signals and of the variations of noises in the signal.
  • a large variance is an indication of interference, and can cause a reduction of the detection speed for certain parameter sets.
  • Also performed in the stage 20 is a further, derived, analysis, in which it is calculated whether the sensor signal mainly increases over a relatively long period of, for example, 40 seconds, i.e., whether it increases monotonically, a monotonic increase of the sensor signal indicating a fire. The result of the derived analysis is used, in the case of some parameter sets, to adjust the speed of the signal processing.
  • the signal processing speed can be quadrupled in order to achieve a more sensitive parameter set.
  • the monotony is determined in that, from a number of, for example, 20 values of the sensor signal, certain pairs (V n ) and (V n-5 ) for example, the first (V 1 ) and the sixth (V 6 ), the sixth (V 6 ) and the eleventh (V 11 ) value, and so forth, are selected, and the differences (V n - V n-5 ) are formed.
  • a difference V n - V n-5 > 0 corresponds to a monotonic increase of the sensor signal, and this is an indication of fire.
  • a stage termed a slope regulator 22 for regulating the signal shape.
  • the fire type, the so-called interference criterion, the so-called monotony criterion and the significance of the temperature are determined in the evaluation stage 21.
  • the fire type is determined on the basis of the BW / FW ratio, possible types being smouldering fire, open fire or transient fire.
  • transient fire refers to the transition from smouldering fire to open fire, when ignition of the fire is detected.
  • the interference calculated from the standard deviation is compared with a threshold value.
  • the monotony of the sensor signal calculated in the derived analysis in the extraction stage 20, is compared with a threshold value.
  • the significance of the temperature is determined by comparison of the output signal of the temperature difference stage 16. An output signal > 20° means a significant temperature increase.
  • the output of the evaluation stage 21 is supplied to an event regulator 23, which controls both the slope regulator 22 and the maximum temperature 17.
  • the system decides whether and, if applicable, how the signal processing is to be modified. Such a modification is performed in the slope regulator 22, which constitutes an intelligent limiter of the increase/decrease of the sensor signal, and additionally determines the symmetry and gradient of the sensor signal.
  • Two signals being, on the one hand, a smoke value S' obtained by the processing just described and, on the other hand, a slow smoke Signal S + , obtained by a very slow filtering, are provided at the output of the slope regulator 22.
  • the smoke value S' is used for the further processing and, inter alia, is supplied to a bypass adder 25, to which the slow smoke signal S + is also supplied.
  • the smoke value S' is limited to a value which is dependent on the respective parameter set and to which the slow smoke value S + is then added in the bypass adder 25, the rise of the slow smoke signal S + being dependent on the respective parameter set and being less in the case of a robust parameter set than in the case of a sensitive parameter set.
  • the bypass adder thus serves, in the case of a robust parameter set, to prevent an excessively prompt alarm in the case of a rapidly increasing smoke value S', and, in the case of a sensitive parameter set, to support the triggering of an alarm in the case of a slowly rising smoke value S'.
  • the smoke value S' and the Temperature value T' are each processed in the form of two values, W os and W op , and W ts and W tp , respectively, wherein:
  • both a summation 26 and a multiplication 27 have the advantage that, in the case of the summation 26, an alarm is triggered in the case of a high temperature value and also only a low smoke value, and, in the case of the multiplication 27, also in the case of a low temperature value and a low smoke value.
  • the corresponding values are added and multiplied, which, together with the signal of the bypass adder 25 and the temperature value T', produces four signals which are supplied to a hazard-signal composition 28. From the four supplied signals, the latter selects, as an alarm signal, the signal having the highest value.
  • a hazard-level acquisition 29 following the hazard-signal composition 28, the signal of the hazard-signal composition 28 is assigned to individual hazard levels and, in a hazard-level verification 30, a check is performed to determine whether the respective hazard level is exceeded over a defined period of, for example, 20 seconds. If this is the case, an alarm is triggered.
  • the connections, indicated by broken lines, from the event regulator 23 to the maximum temperature 17, to the slope regulator 22, to the multiplication 27 and to the hazard-level verification 30 represent control lines.
  • the relation Q is supplied to the evaluation stage 21 and is used there to determine the type of fire so that the event controller 23 can take the necessary steps for a possible change of the signal processing. Additionally, the relation Q is also supplied to the hazard-level acquisition 29 and is multiplied with the alarm threshold. That means in other words a weighting of the alarm threshold depending on the type of the detected fire.
EP04017433A 2004-07-23 2004-07-23 Streulichtrauchmelder Withdrawn EP1619640A1 (de)

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EP04017433A EP1619640A1 (de) 2004-07-23 2004-07-23 Streulichtrauchmelder

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011108390A1 (de) 2011-07-22 2013-01-24 PPP "KB Pribor" Ltd. Verfahren zur Herstellung eines Rauchdetektors vom offenen Typ und Rauchdetektor
DE102011108389A1 (de) 2011-07-22 2013-01-24 PPP "KB Pribor" Ltd. Rauchdetektor
WO2013142504A1 (en) * 2012-03-19 2013-09-26 Kla-Tencor Corporation Methods and apparatus for spectral luminescence measurement
EP3287999A1 (de) * 2016-08-25 2018-02-28 Siemens Schweiz AG Verfahren zur branddetektion nach dem streulichtprinzip mit gestaffelter zuschaltung einer weiteren led-einheit zum einstrahlen weiterer lichtimpulse unterschiedlicher wellenlänge und streulichtwinkel sowie derartige streulichtrauchmelder
EP4332936A1 (de) * 2022-08-08 2024-03-06 Carrier Corporation Einwellen-mehrwinkel-rauchalarmalgorithmus

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5293049A (en) * 1991-05-01 1994-03-08 Alliedsignal Inc. Aerosol discriminator for particle discrimination
US6218950B1 (en) * 1999-01-21 2001-04-17 Caradon Esser Gmbh Scattered light fire detector
US20040066512A1 (en) * 2002-10-07 2004-04-08 Heiner Politze Fire detection method and fire detector therefor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5293049A (en) * 1991-05-01 1994-03-08 Alliedsignal Inc. Aerosol discriminator for particle discrimination
US6218950B1 (en) * 1999-01-21 2001-04-17 Caradon Esser Gmbh Scattered light fire detector
US20040066512A1 (en) * 2002-10-07 2004-04-08 Heiner Politze Fire detection method and fire detector therefor

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011108390A1 (de) 2011-07-22 2013-01-24 PPP "KB Pribor" Ltd. Verfahren zur Herstellung eines Rauchdetektors vom offenen Typ und Rauchdetektor
DE102011108389A1 (de) 2011-07-22 2013-01-24 PPP "KB Pribor" Ltd. Rauchdetektor
WO2013014577A2 (de) 2011-07-22 2013-01-31 Shustrov Sergei Vladimirovich Verfahren zur herstellung eines rauchdetektors vom offenen typ und rauchdetektor
WO2013014561A1 (de) 2011-07-22 2013-01-31 Shustrov Sergei Vladimirovich Pulsbetriebener rauchdetektor mit digitaler steuereinheit
DE102011108390B4 (de) 2011-07-22 2019-07-11 PPP "KB Pribor" Ltd. Verfahren zur Herstellung eines Rauchdetektors vom offenen Typ
WO2013142504A1 (en) * 2012-03-19 2013-09-26 Kla-Tencor Corporation Methods and apparatus for spectral luminescence measurement
US9410890B2 (en) 2012-03-19 2016-08-09 Kla-Tencor Corporation Methods and apparatus for spectral luminescence measurement
EP3287999A1 (de) * 2016-08-25 2018-02-28 Siemens Schweiz AG Verfahren zur branddetektion nach dem streulichtprinzip mit gestaffelter zuschaltung einer weiteren led-einheit zum einstrahlen weiterer lichtimpulse unterschiedlicher wellenlänge und streulichtwinkel sowie derartige streulichtrauchmelder
WO2018036754A1 (de) * 2016-08-25 2018-03-01 Siemens Schweiz Ag Verfahren zur branddetektion nach dem streulichtprinzip mit gestaffelter zuschaltung einer weiteren led-einheit zum einstrahlen weiterer lichtimpulse unterschiedlicher wellenlänge und streulichtwinkel sowie derartige streulichtrauchmelder
US10685546B2 (en) 2016-08-25 2020-06-16 Siemens Schweiz Ag Fire detection using the scattered light principle with a staggered activation of a further LED unit for radiating in further light pulses with different wavelengths and scattered light angles
EP4332936A1 (de) * 2022-08-08 2024-03-06 Carrier Corporation Einwellen-mehrwinkel-rauchalarmalgorithmus

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