EP0127645B1 - Fire alarm and electrode device therefor - Google Patents

Fire alarm and electrode device therefor Download PDF

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Publication number
EP0127645B1
EP0127645B1 EP83903778A EP83903778A EP0127645B1 EP 0127645 B1 EP0127645 B1 EP 0127645B1 EP 83903778 A EP83903778 A EP 83903778A EP 83903778 A EP83903778 A EP 83903778A EP 0127645 B1 EP0127645 B1 EP 0127645B1
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Prior art keywords
electrode
measuring
electrodes
counter
fire detector
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German (de)
French (fr)
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EP0127645A1 (en
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Hans-Christoph Siegmann
Heinz Burtscher
Andreas Schmidt-Ott
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SLM Investissements SA
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SLM Investissements SA
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • 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

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  • the invention relates to a fire detector with at least two electrodes 1, 2, between which an electric field is generated by a DC voltage source 4, the opposing electrode surfaces delimiting a measuring space through which the air moved by convection can sweep through a room to be monitored, wherein one of the electrodes is designed as a measuring electrode and the other as a counterelectrode and at least one of the electrodes 1, 2 is provided with a circulation opening 11 for the ambient air to be monitored and / or consists of a plurality of partial electrodes 15 arranged in this way with gaps, whereby by these spaces can flow ambient air into the measuring space 9, 9a.
  • Fire detectors of a similar type are known and used in various designs. So shows z. B. US Pat. No. 2,408,051 (Donelian) describes a fire detector with two measuring rooms, small particles and small ions being “filtered out” electrically in the first measuring room and the air being ionized in the second measuring room with the aid of a radioactive preparation. The resulting conductivity is reduced if smoke is present because ions attach to the difficult-to-move smoke particles. If the reduction in conductivity in the ionization chamber reaches a threshold, the alarm is triggered. In the aforementioned US Pat. No.
  • the electrodes which delimit the measuring spaces are connected in series in the manner of a capacitive voltage divider between the positive and negative poles of a DC voltage source.
  • relatively low field strengths of about 40 or 50 volts / cm are provided in the first measuring room.
  • the fire detector according to this US-PS requires the two measuring chambers, whereby the disadvantage of the second measuring chamber provided with radioactive material is already known with regard to environmental influences.
  • the arrangement is also complex in construction.
  • Ion measuring devices or measuring arrangements for determining the mobility of particles are known, as is the case e.g. from US-PS 4114088, but so far the use of such measuring devices as fire detectors has not been proposed, nor are they suitable for such use due to the design. Rather, fire detectors with ionization chambers dominate, especially using radioactive preparations, although the need for simplified fire detectors that are less polluting and, above all, work without radioactive substances has been constant and has existed for a long time. This is also evident from Scheidweiler's article in “Dust Cleanliness Air, Vol. 32 No. 11 November, 1972technische
  • a fire detector is also known, with at least two electrodes, between which an electric field is generated by a DC voltage source, the opposite electrode surfaces delimiting a measuring space through which the air moved by convection is one to be monitored, and wherein one of the electrodes is designed as a measuring electrode and the other as a counter electrode and at least one of the electrodes is provided with circulation openings for the ambient air to be monitored and / or consists of a plurality of partial electrodes arranged in this way with gaps, that ambient air can flow into the measuring space through these spaces.
  • a fire detector only reacts to sudden changes in conductivity in the presence of smoke. Conversely, the fire detector would not react to a net charge of zero, even if the conductivity suddenly changed in the presence of smoke.
  • the invention is accordingly based on the object of providing an improved, highly sensitive and substantially simplified fire detector and an electrode arrangement intended therefor, which can be used for ionization without radioactive preparations.
  • a current measuring arrangement and evaluation circuit is provided, that the fire detector has a compensation electrode which delimits a compensation space and is designed as a shield for the measuring and counter electrodes, and that the DC voltage source, on the one hand, directly or indirectly with the counter electrode and on the other hand, is connected to a current measuring arrangement, and that the measuring electrode is connected to the input of the current measuring arrangement without a direct connection to the direct voltage source.
  • the invention is based for the first time in an optimally simple manner on the principle that smoke particles from burns are in principle highly electrically charged. This is due to the fact that positive and negative small ions attach to the particles. These are constantly formed in the air even in normal environments, especially through cosmic rays and natural radioactivity.
  • the concentration of the particles of radius R with p elementary charges is accordingly
  • n R is the total concentration of the neutral particles with radius R
  • k is the Boltzmann constant
  • T is the absolute temperature.
  • charging the smoke means the mean value of the particle charge.
  • the fire detector according to the invention measures the amount of particle charge of a certain sign and therefore also functions when the net charge of the smoke is zero. With such a charge distribution, there are as many positive as negative ions on the smoke particles. According to the invention, reliable detection of the smoke in the field between the measuring electrode and counterelectrode is now ensured by electrostatically separating positive and negative particles and measuring the charge of a sign or by measuring the change in conductivity caused by the smoke.
  • the electric current thus generated is relatively small at field strengths which do not yet lead to glow discharge, but at least amount to 100 volts / cm, but can easily be measured with electronic amplifiers or small electroscopes.
  • the electrode spacing is advantageously less than 10 mm, but more than 1 mm. It has been shown that this particular dimensioning enables a number of advantageous properties to be achieved: the relatively small measuring space provides good shielding of the measuring electrode against influence by net charge; on the other hand, the distance is large enough to avoid false reports from possibly deposited dust or soot particles. In addition, it has been shown that, with such an electrode spacing, it is also possible to work with voltages in an optimal range, which on the one hand ensure reliable separation and separation of charged particles and on the other hand avoid contamination through constant attraction and deposition of dust particles.
  • the invention is advantageously not based on the measurement of the excess or net charge practiced in known devices, but rather on the charge measurement after electrostatic separation of positive and negative particles.
  • An auxiliary electrode arrangement can advantageously be provided, which pre-separates small and / or charged particles carried by slow flow before they can get into the measuring space. In this way, the sensitivity to small smoke sources that cause small particles and / or only slow convective flow (cigarettes) can be reduced.
  • the net charge suppression can also be achieved or further improved by providing a compensation space that is delimited on the one hand by the measuring electrode and on the other hand by a compensation electrode.
  • the measuring electrode is influenced by the influence of net charge e.g. shielded in large clouds of smoke on both sides and only that is measured in a relatively small volume limited by the measuring space and / or the compensation space.
  • the compensation electrode can simultaneously be designed as a shield for the electrode arrangement.
  • the influences described above by the net charge or by influence can even be completely compensated for if the compensation space is arranged at approximately the same distance from the measuring electrode as the measurement space and is also able to absorb approximately the same volume of ambient air flowing through. This means that the influence of gases flowing in the measuring space with a high net charge is compensated for by the influence of reversed polarity caused by gases flowing away in the compensation space.
  • Compensation can also advantageously be achieved if the measuring electrode is arranged with respect to the air flow in such a way that the air flow sweeps the measuring electrode twice, but from opposite sides ten strikes, or flows through the electrode, so that influence currents, which occur due to net charge of the ambient air passing through or of smoke clouds in the measuring electrode, are compensated for.
  • the electrode is designed as an electrically closed circle transverse to the direction of flow.
  • an electrode arrangement for the fire detector according to the invention is a measuring electrode and / or compensation electrode designed as a grid; this facilitates convection and prevents the air or gas in the measuring room from becoming depleted of charges. In addition, it is ensured that, especially in connection with the principle of compensation through a compensation space and / or double flow through the measuring electrode described above, simple compensation of net charge influences is made possible.
  • the measuring electrode can also be constructed from a plurality of electrically connected partial electrodes through which air or gas clouds flow in such a way that the influences of influence caused by the net charge in the partial electrodes cancel each other out.
  • the measuring electrode is arranged between two counter electrodes, the two counter electrodes being connected to the direct voltage source and the measuring electrode being provided between the counter electrodes and being connected to the input of the measuring arrangement. It is thereby achieved that the fields in the two measuring spaces between the two counter electrodes and the measuring electrode run symmetrically to the latter, i.e. in other words, particles of the same polarity charged from both measuring rooms hit the measuring electrode. This guarantees high sensitivity in particular.
  • the measuring electrode is connected to the input of the measuring arrangement and is therefore virtually at the potential of the other side of the measuring arrangement. It can advantageously be mechanically rigidly connected to an electrode housing and / or the counter electrodes by means of insulation elements, the insulation elements being interrupted by electrically conductive parts which are connected to the other side of the measuring electrode. This prevents leakage currents from being measured on the insulation elements.
  • FIG. 1 shows the basic illustration of a fire detector according to the invention with a measuring electrode 1, a counter electrode 2, a schematically illustrated measuring arrangement 3, which at the same time serves to trigger the alarm in a known manner, and its DC voltage source 4.
  • Measuring electrode 1 and counter electrode 2 are fastened by means of insulation elements 6 to a holder 7, which in turn is connected to a base plate 8.
  • the holder 7 is electrically conductive and is grounded, so that no leakage currents can flow between the measuring electrode 1 and the counterelectrode 2 via the insulation elements 6, since the measuring electrode is - but only virtually - at ground potential via the measuring arrangement 3. This is advantageous in view of the extremely low flowing currents.
  • the distance between the measuring electrode 1 and counter electrode 2 is 5 mm, the voltage of the direct voltage source 4 is 500 volts, so that there is a field strength of 1000 volts / cm between the two electrodes 1 and 2. If now charged smoke particles get into the measuring space 9 between the measuring electrode 1 and the counter electrode 2, the electric field causes the positive and negative particles to move to the two electrodes. This charge movement (charge drift) influences a current into the measuring electrode 1, which is measured in the measuring arrangement 3.
  • the measuring electrodes 1 and the counter electrode 2 are designed as approximately square plates with an area of 40 cm 2 each. Of course, the area of the electrodes can be changed depending on the requirement and the desired sensitivity of the measuring arrangement, as can also be seen, for example, from the exemplary embodiment according to FIG.
  • the overall arrangement is surrounded by a shield 5, which is also grounded. This not only ensures mechanical protection of the arrangement, but also influences of errors due to net charging of a schematically indicated smoke cloud 30 are compensated to the extent that influences from the charge cloud outside the shield 5 are kept away from the measuring electrode 1 and thus no influence currents can arise.
  • both the measuring electrode 1 and the counter electrode 2 are provided with a multiplicity of holes 11, which allow the smoke to flow through the measuring space 9 coming from the horizontal direction as well as from the vertical direction solely due to the convection.
  • Figure 2 shows an arrangement in which the base plate 8 is arranged as a compensation electrode in parallel and at the same distance as the counter electrode 2 to the measuring electrode 1.
  • Base plate 8, measuring electrode 1 and counter electrode 2 are (part not shown) each formed as a perforated plate. Due to the arrangement, flowing gas clouds with a net charge are initially shielded from the outside by the shield 5. In addition, there is approximately the same amount of gas flowing through each in the measurement space 9 and in the compensation space 10, as a result of which the amount of influence by net charge is approximately the same. However, since gas flowing through in the direction of the arrow moves towards the measuring electrode 1 in the measuring space 9, but moves away from the measuring electrode 1 in the compensation space 10, the resulting influencing currents each have opposite polarity, so that the effects of net charge are compensated for.
  • FIG. 3 shows an exemplary embodiment in which two counter electrodes 2 enclose a measuring electrode 1 between them and thereby delimit two measuring spaces 9 and 9 '.
  • the counter electrodes 2 are designed as perforated plates, lie on ground and at the same time serve to shield the arrangement from the outside.
  • the measuring electrode 1 is fastened to the base plate 8 by an insulator arrangement, not shown. Since both counter electrodes 2 are at the same potential with respect to the measuring electrode 1, the field distribution is symmetrical, i.e. that both in the measuring space 9 and in the measuring space 9 ′, ions of negative polarity drift onto the measuring electrode 1 and the resulting influent current in the measuring arrangement 3 can be determined.
  • the sensitivity of the arrangement is increased due to the two measuring rooms 9 and 9 '. In addition, compensation of net charge influences is ensured by the symmetry of the arrangement.
  • Figure 4 shows an arrangement in which a cylindrical, symmetrical design of all parts, i.e. the shield 5, the measuring electrode 1 and the counter electrodes 2 is provided.
  • the outer of the two counter electrodes 2 is fastened to the shield 5 by means of bolts 12 made of insulation material.
  • the measuring electrode 1 and the second counter electrode 2 are mechanically connected to one another by means of insulation elements 13a, 13b, which are also bolt-shaped.
  • a metal disk 14 is arranged between the insulation elements 13a and 13b, which lies on ground. Leakage currents between the counter electrodes 2 and the measuring electrode 1 are thus avoided.
  • the cylindrical configuration of the counter electrode 2 with a base plate 2a which also corresponds to the configuration of the other counter electrode 2 or the measuring electrode 1 and the shield 5, is shown schematically in the upper section of FIG. 4.
  • This arrangement also has the advantage that the insulation elements are not directly exposed to the air flow and are therefore protected against contamination.
  • a gas cloud with charged smoke particles flowing through the arrangement in the direction of the arrow strikes the outside of the measuring electrode 1 (at A) coming from the right and the inside of the measuring electrode 1 (at B) before leaving the arrangement. Since the measuring electrode 1 is cylindrical and constitutes a closed circuit, influence currents due to net charge will accordingly have opposite polarity and will be automatically compensated.
  • shield 5 which is also designed as a perforated plate
  • outer counter electrode 2 delimit an annular compensation space 14, which, however, has a smaller field strength than the two measurement spaces 9 and 9 'due to the greater distance. Small, slowly flowing charged particles are therefore already separated in the compensation space 14 before they reach the measurement space 9 or 9 '. This results in a size-selective pre-separation, which can be of great advantage to reduce false alarms.
  • FIG. 5 shows an exemplary embodiment of a measuring electrode which consists of a plurality of punched-out sheet metal strips 15 which are connected to one another by means of an electrically conductive rail 16.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Business, Economics & Management (AREA)
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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

Fire alarm with a measure chamber (9, 9') limited by two electrodes (1, 2), an electric field being generated between the electrodes by a direct voltage source. The measure electrode (1) has no direct connection with the direct voltage source (4) at the input of a current measuring unit (3). As soon as smoke laden particles enter the measure chamber (9) between the electrodes, the electric field causes a displacement of positive and negative particles. Due to said charge displacement (charge drift), a current is induced in the measure electrode, current which is measured.

Description

Die Erfindung betrifft einen Brandmelder mit wenigstens zwei Elektroden 1, 2, zwischen denen durch eine Gleichspannungsquelle 4 ein elektrisches Feld erzeugt wird, wobei die einander gegenüberliegenden Elektroden-Oberflächen einen Messraum begrenzen, durch welchen die durch Konvektion bewegte Luft eines zu überwachenden Raumes streichen kann, wobei eine der Elektroden als Messelektrode und die andere als Gegenelektrode ausgebildet ist und wenigstens eine der Elektroden 1, 2 mit Zirkulations-Öffnung 11 für die zu überwachende Umgebungsluft versehen ist und/oder aus einer Mehrzahl von derart mit Zwischenräumen angeordneten Teilelektroden 15 besteht, wobei durch diese Zwischenräume Umgebungsluft in den Messraum 9, 9a strömen kann.The invention relates to a fire detector with at least two electrodes 1, 2, between which an electric field is generated by a DC voltage source 4, the opposing electrode surfaces delimiting a measuring space through which the air moved by convection can sweep through a room to be monitored, wherein one of the electrodes is designed as a measuring electrode and the other as a counterelectrode and at least one of the electrodes 1, 2 is provided with a circulation opening 11 for the ambient air to be monitored and / or consists of a plurality of partial electrodes 15 arranged in this way with gaps, whereby by these spaces can flow ambient air into the measuring space 9, 9a.

Brandmelder vergleichbarer Art sind in verschiedenen Ausführungen bekannt und gebräuchlich. So zeigt z. B. die US-PS 2 408 051 (Donelian) einen Brandmelder mit zwei Messräumen, wobei im ersten Messraum Kleinteilchen und KleinIonen elektrisch «herausgefiltert» werden und im zweiten Messraum die Luft mit Hilfe eines radioaktiven Präparats ionisiert wird. Die so entstehende Leitfähigkeit wird beim Vorhandensein von Rauch reduziert, weil sich Ionen an die schwer beweglichen Rauchteilchen anlagern. Erreicht die Reduktion der Leitfähigkeit in der lonisationskammer eine Schwelle, so wird der Alarm ausgelöst. Bei der genannten US-PS 2 408 051 sind dabei die Elektroden, welche die Messräume begrenzen, nach Art eines kapazitiven Spannungsteilers in Serie zwischen den Plus- bzw. den Minuspol einer Gleichspannungsquelle angeschlossen. Ausserdem sind relativ niedrige Feldstärken von etwa 40 oder 50 Volt/cm im ersten Messraum vorgesehen. Der Brandmelder gemäss dieser US-PS benötigt zwingend die beiden Messkammern, wobei der Nachteil der mit radioaktivem Stoff versehenen zweiten Messkammer schon im Hinblick auf Umwelteinflüsse bekannt ist. Die Anordnung ist ausserdem aufwendig in der Konstruktion.Fire detectors of a similar type are known and used in various designs. So shows z. B. US Pat. No. 2,408,051 (Donelian) describes a fire detector with two measuring rooms, small particles and small ions being “filtered out” electrically in the first measuring room and the air being ionized in the second measuring room with the aid of a radioactive preparation. The resulting conductivity is reduced if smoke is present because ions attach to the difficult-to-move smoke particles. If the reduction in conductivity in the ionization chamber reaches a threshold, the alarm is triggered. In the aforementioned US Pat. No. 2,408,051, the electrodes which delimit the measuring spaces are connected in series in the manner of a capacitive voltage divider between the positive and negative poles of a DC voltage source. In addition, relatively low field strengths of about 40 or 50 volts / cm are provided in the first measuring room. The fire detector according to this US-PS requires the two measuring chambers, whereby the disadvantage of the second measuring chamber provided with radioactive material is already known with regard to environmental influences. The arrangement is also complex in construction.

Aus der US-PS 3 754 219 (Klein) ist ein Gerät zur Ermittlung von Luftverschmutzung oder Rauch ersichtlich, bei welchem die Überschussladung («net charge») gemessen wird. Die Überschussladung schwankt aber bei Bränden derart stark, dass ein auf diesem Prinzip arbeitender Brandmelder praktisch nicht einsetzbar ist. Gleiches gilt für den Feuer- und Rauchdetektor gemäss US-PS 3 470 551 (Jaffe et al).From US Pat. No. 3,754,219 (Klein) a device for determining air pollution or smoke can be seen, in which the excess charge (“net charge”) is measured. In the case of fires, however, the excess charge fluctuates so much that a fire detector working on this principle cannot be used in practice. The same applies to the fire and smoke detector according to US Pat. No. 3,470,551 (Jaffe et al).

Zwar sind lonenmessgeräte oder Messanordnungen zur Ermittlung der Beweglichkeit von Partikeln bekannt, wie dies z.B. aus der US-PS 4114088 hervorgeht, doch ist bislang weder der Einsatz derartiger Messgeräte als Brandmelder vorgeschlagen worden, noch eignen sie sich aufgrund der konstruktiven Ausbildung für einen solchen Einsatz. Vielmehr dominieren Feuermelder mit Ionisationskammern, insbesondere unter Verwendung radioaktiver Präparate, obwohl der Bedarf nach vereinfachten, die Umwelt weniger belastenden und vor allem ohne radioaktive Stoffe arbeitenden Brandmeldern konstant und seit langem besteht. Dies geht auch aus dem Aufsatz von Scheidweiler in «Staub-Reinhalt.-Luft, Vol. 32 No. 11 November, 1972» hervor.Ion measuring devices or measuring arrangements for determining the mobility of particles are known, as is the case e.g. from US-PS 4114088, but so far the use of such measuring devices as fire detectors has not been proposed, nor are they suitable for such use due to the design. Rather, fire detectors with ionization chambers dominate, especially using radioactive preparations, although the need for simplified fire detectors that are less polluting and, above all, work without radioactive substances has been constant and has existed for a long time. This is also evident from Scheidweiler's article in “Dust Cleanliness Air, Vol. 32 No. 11 November, 1972 ».

Aus der US-A-3 262 106 ist ferner ein Brandmelder bekannt, mit wenigstens zwei Elektroden, zwischen denen durch eine Gleichspannungsquelle ein elektrisches Feld erzeugt wird, wobei die einander gegenüberliegenden Elektroden-Oberflächen einen Messraum begrenzen, durch welchen die durch Konvektion bewegte Luft eines zu überwachenden Raumes streichen kann, und wobei eine der Elektroden als Messelektrode und die andere als Gegenelektrode ausgebildet ist und wenigstens eine der Elektroden mit Zirkulations-Öffnungen für die zu überwachende Umgebungsluft versehen ist und/oder aus einer Mehrzahl von derart mit Zwischenräumen angeordneten Teilelektroden besteht, dass durch diese Zwischenräume Umgebungsluft in den Messraum strömen kann. Ein solcher Brandmelder reagiert jedoch nur auf plötzliche Änderungen der Leitfähigkeit in Anwesenheit von Rauch. Umgekehrt würde der Brandmelder auf eine Nettoladung Null nicht reagieren, auch wenn sich die Leitfähigkeit in Anwesenheit von Rauch plötzlich ändern würde.From US-A-3 262 106 a fire detector is also known, with at least two electrodes, between which an electric field is generated by a DC voltage source, the opposite electrode surfaces delimiting a measuring space through which the air moved by convection is one to be monitored, and wherein one of the electrodes is designed as a measuring electrode and the other as a counter electrode and at least one of the electrodes is provided with circulation openings for the ambient air to be monitored and / or consists of a plurality of partial electrodes arranged in this way with gaps, that ambient air can flow into the measuring space through these spaces. However, such a fire detector only reacts to sudden changes in conductivity in the presence of smoke. Conversely, the fire detector would not react to a net charge of zero, even if the conductivity suddenly changed in the presence of smoke.

Der Erfindung liegt dementsprechend die Aufgabe zugrunde, einen verbesserten, hoch sensitiven und wesentlich vereinfachten Brandmelder sowie eine dafür bestimmte Elektrodenanordnung zu schaffen, die ohne radioaktive Präparate zur lonisation einsetzbar ist.The invention is accordingly based on the object of providing an improved, highly sensitive and substantially simplified fire detector and an electrode arrangement intended therefor, which can be used for ionization without radioactive preparations.

Erfindungsgemäss wird dies dadurch erreicht, dass eine Strom-Messanordnung und Auswertungsschaltung vorgesehen ist, dass der Brandmelder eine Kompensationselektrode aufweist, welche einen Kompensationsraum begrenzt und als Abschirmung der Mess- und Gegenelektrode ausgebildet ist, und dass die Gleichspannungsquelle einerseits direkt oder indirekt mit der Gegenelektrode und andererseits mit einer Strom-Messanordnung verbunden ist, und dass die Messelektrode ohne direkte Verbindung mit der Gleichspannungsquelle an den Eingang der Strom-Messanordnung angeschlossen ist.According to the invention, this is achieved in that a current measuring arrangement and evaluation circuit is provided, that the fire detector has a compensation electrode which delimits a compensation space and is designed as a shield for the measuring and counter electrodes, and that the DC voltage source, on the one hand, directly or indirectly with the counter electrode and on the other hand, is connected to a current measuring arrangement, and that the measuring electrode is connected to the input of the current measuring arrangement without a direct connection to the direct voltage source.

Die Erfindung geht dabei erstmals in optimal einfacher Weise von dem Prinzip aus, dass Rauchteilchen aus Verbrennungen prinzipiell stark elektrisch geladen sind. Dies rührt daher, dass sich positive und negative Kleinionen an die Teilchen anlagern. Diese werden schon in normaler Umgebung ständig in der Luft gebildet, insbesondere durch kosmische Strahlung und natürliche Radioaktivität. Die Wahrscheinlichkeit dafür, dass ein Teilchen vom Radius R im thermodynamischen Gleichgewicht die Ladung q = p · e besitzt, ist mit der Coulombenenergie p2e2/2R durch das Boltzmanngesetz gegeben. Die Konzentration der Teilchen vom Radius R mit p Elementarladungen ist demnachThe invention is based for the first time in an optimally simple manner on the principle that smoke particles from burns are in principle highly electrically charged. This is due to the fact that positive and negative small ions attach to the particles. These are constantly formed in the air even in normal environments, especially through cosmic rays and natural radioactivity. The probability that a particle of radius R has the charge q = p · e in thermodynamic equilibrium is given by the Coulomb energy p 2 e 2 / 2R by the Boltzmann law. The concentration of the particles of radius R with p elementary charges is accordingly

Figure imgb0001
wobei nR die Gesamtkonzentration der neutralen Teilchen mit Radius R ist, k die Boltzmannkonstante und T die absolute Temperatur. Daraus folgt für den quadratischen Mittelwert
Figure imgb0002
(2) berücksichtigt allerdings nicht die diskrete Natur der Ladung und ist für Teilchen mit R < 0,1 pm, die nur wenige Elementarladungen tragen, ungenau. Bei gleicher Konzentration von gleich beweglichen positiven und negativen Ionen stellt sich eine stationäre Teilchenladungsverteilung ein, die der Boltzmannverteilung entspricht. Die mittlere Partikelladung ist bei Boltzmannverteilung exakt null und in der Luft im stationären Fall wenig verschieden von null, da negative Kleinionen einen ca. 20% höheren Anlagerungskoeffizienten haben als positive.
Figure imgb0001
 where n R is the total concentration of the neutral particles with radius R, k is the Boltzmann constant and T is the absolute temperature. From this follows for the quadratic mean
Figure imgb0002
 However, (2) does not take into account the discrete nature of the charge and is inaccurate for particles with R <0.1 pm that carry only a few elementary charges. With the same concentration of equally movable positive and negative ions, a stationary particle charge distribution is obtained which corresponds to the Boltzmann distribution. The average particle charge is exactly zero for Boltzmann distribution and little different from zero in stationary air, since negative small ions have an approx. 20% higher deposition coefficient than positive ones.

Es ist an sich schon bekannt, dass aus einer Verbrennung stammende Rauchteilchen besonders stark elektrisch geladen sind. Das ist schon dadurch verständlich, dass in einer Flamme infolge verschiedener Prozesse eine grosse Kleinionenkonzentration herrscht und laut Boltzmanngesetz eine hohe Temperatur zu hoher Teilchenladung führt. Ist der Rauch dicht (typ. bei Feuer: 107 Teilchen/cm3), so bleibt eine erhöhte Aufladung noch lang erhalten, bevor sich das Boltzmanngleichgewicht bei Zimmertemperatur einstellt, da die Kleinionennachlieferung zur Neutralisierung der Teilchen klein ist. Obwohl gerade bei Flammenaerosolen noch andere Aufladungsmechanismen in Frage kommen, kann allgemein gesagt werden:

  • (1) Jedes in der Umwelt vorkommende Aerosol besitzt nach langer Zeit mindestens die Aufladung der Boltzmannverteilung bei Umgebungstemperatur, und
  • (2) dichter Rauch, der aus einer heissen Zone mit grosser lonenkonzentration (Flamme) stammt, besitzt eine Aufladung, die grösser ist als die unter (1) genannte und behält diese während langer Zeit.
It is known per se that smoke particles originating from combustion are particularly strongly electrically charged. This is understandable because there is a large concentration of small ions in a flame as a result of various processes and, according to the Boltzmann law, a high temperature leads to a high particle charge. If the smoke is dense (typically in the case of fire: 10 7 particles / cm 3 ), an increased charge is maintained for a long time before the Boltzmann equilibrium is established at room temperature, since the small ion supply to neutralize the particles is small. Although there are other charging mechanisms in particular for flame aerosols, it can generally be said:
  • (1) Every aerosol occurring in the environment has at least the charge of the Boltzmann distribution at ambient temperature after a long time, and
  • (2) Dense smoke that comes from a hot zone with a high ion concentration (flame) has a charge that is greater than that mentioned under (1) and retains it for a long time.

Man beachte, dass hier unter «Aufladung des Rauchs» der Mittelwert des Betrags der Teilchenladung gemeint ist. Der erfindungsgemässe Brandmelder misst den Betrag der Teilchenladung eines bestimmten Vorzeichens, funktioniert also auch, wenn die Nettoladung des Rauchs null ist. Bei einer solchen Ladungsverteilung sitzen gleich viele positive wie negative Ionen auf den Rauchteilchen. Erfindungsgemäss wird nun eine sichere Detektion des Rauchs im Feld zwischen Messelektrode und Gegenelektrode durch elektrostatische Trennung positiver und negativer Teilchen und Messung der Ladung eines Vorzeichens oder durch Messung der durch den Rauch hervorgerufenen Änderung der Leitfähigkeit gewährleistet. Der so entstehende elektrische Strom ist bei Feldstärken, die noch nicht zu Glimmendladungen führen, wenigstens jedoch 100 Volt/cm betragen, zwar relativ klein, jedoch ohne weiteres mit elektronischen Verstärkern oder kleinen Elektroskopen messbar.It should be noted that “charging the smoke” means the mean value of the particle charge. The fire detector according to the invention measures the amount of particle charge of a certain sign and therefore also functions when the net charge of the smoke is zero. With such a charge distribution, there are as many positive as negative ions on the smoke particles. According to the invention, reliable detection of the smoke in the field between the measuring electrode and counterelectrode is now ensured by electrostatically separating positive and negative particles and measuring the charge of a sign or by measuring the change in conductivity caused by the smoke. The electric current thus generated is relatively small at field strengths which do not yet lead to glow discharge, but at least amount to 100 volts / cm, but can easily be measured with electronic amplifiers or small electroscopes.

Vorteilhafterweise beträgt der Elektrodenabstand weniger als 10 mm, jedoch mehr als 1 mm. Es hat sich nämlich gezeigt, dass durch diese besondere Dimensionierung eine Mehrzahl von vorteilhaften Eigenschaften erreichbar ist: Der relativ kleine Messraum bewirkt eine gute Abschirmung der Messelektrode gegen Influenz durch Nettoladung; andererseits ist der Abstand genügend gross, um Fehlmeldungen durch eventuell abgelagerte Staub- oder Russpartikel zu vermeiden. Zudem hat sich gezeigt, dass bei einem derartigen Elektrodenabstand auch mit Spannungen in einem optimalen Bereich gearbeitet werden kann, die einerseits zuverlässige Trennung und Abscheidung geladener Teilchen gewährleisten und andererseits Verschmutzung durch konstante Anziehung und Ablagerung von Staubpartikeln vermeiden.The electrode spacing is advantageously less than 10 mm, but more than 1 mm. It has been shown that this particular dimensioning enables a number of advantageous properties to be achieved: the relatively small measuring space provides good shielding of the measuring electrode against influence by net charge; on the other hand, the distance is large enough to avoid false reports from possibly deposited dust or soot particles. In addition, it has been shown that, with such an electrode spacing, it is also possible to work with voltages in an optimal range, which on the one hand ensure reliable separation and separation of charged particles and on the other hand avoid contamination through constant attraction and deposition of dust particles.

Die Erfindung beruht vorteilhafterweise nicht auf der bei bekannten Geräten praktizierten Messung der Überschuss- oder Nettoladung, sondern auf der Ladungsmessung nach elektrostatischer Trennung positiver und negativer Teilchen.The invention is advantageously not based on the measurement of the excess or net charge practiced in known devices, but rather on the charge measurement after electrostatic separation of positive and negative particles.

Vorteilhafterweise kann eine Hilfs-Elektrodenanordnung vorgesehen werden, welche kleine und/oder durch langsame Strömung getragene geladene Teilchen vorabscheidet, bevor sie in den Messraum gelangen können. Auf diese Weise kann die Empfindlichkeit auf kleine Rauchquellen, die kleine Teilchen und/oder nur langsame konvektive Strömung hervorrufen (Zigaretten), reduziert werden.An auxiliary electrode arrangement can advantageously be provided, which pre-separates small and / or charged particles carried by slow flow before they can get into the measuring space. In this way, the sensitivity to small smoke sources that cause small particles and / or only slow convective flow (cigarettes) can be reduced.

Die Nettoladungsunterdrückung lässt sich auch dadurch erreichen oder noch weiter verbessern, dass ein Kompensationsraum vorgesehen ist, der einerseits durch die Messelektrode und andererseits durch eine Kompensationselektrode begrenzt wird. Dadurch wird die Messelektrode von der Influenz durch Nettoladung z.B. in grossen Rauchwolken auf beiden Seiten abgeschirmt und es wird nur diejenige in einem relativ kleinen, durch den Messraum und/oder den Kompensationsraum beschränkten Volumen gemessen. Vorteilhafterweise kann dabei die Kompensationselektrode gleichzeitig als Abschirmung der Elektrodenanordnung ausgebildet sein.The net charge suppression can also be achieved or further improved by providing a compensation space that is delimited on the one hand by the measuring electrode and on the other hand by a compensation electrode. As a result, the measuring electrode is influenced by the influence of net charge e.g. shielded in large clouds of smoke on both sides and only that is measured in a relatively small volume limited by the measuring space and / or the compensation space. Advantageously, the compensation electrode can simultaneously be designed as a shield for the electrode arrangement.

Die vorstehend beschriebenen Einflüsse durch die Nettoladung bzw. durch Influenz lassen sich sogar vollständig kompensieren, wenn der Kompensationsraum mit etwa gleichem Abstand zur Messelektrode angeordnet ist wie der Messraum und auch etwa gleiche Volumen durchströmender Umgebungsluft aufzunehmen imstande ist. Dadurch wird nämlich erreicht, dass die Influenz durch im Messraum zuströmende Gase mit hoher Nettoladung ausgeglichen wird durch die Influenz mit umgekehrter Polarität durch im Kompensationsraum wegströmende Gase.The influences described above by the net charge or by influence can even be completely compensated for if the compensation space is arranged at approximately the same distance from the measuring electrode as the measurement space and is also able to absorb approximately the same volume of ambient air flowing through. This means that the influence of gases flowing in the measuring space with a high net charge is compensated for by the influence of reversed polarity caused by gases flowing away in the compensation space.

Vorteilhaft lässt sich auch Kompensation erreichen, wenn die Messelektrode in bezug auf den Luftstrom derart angeordnet ist, dass der Luftstrom die Messelektrode zweimal bestreicht, dabei jedoch von jeweils gegenüberliegenden Seiten auftrifft, bzw. die Elektrode durchströmt, so dass Influenzströme, die durch Nettoladung der durchtretenden Umgebungsluft bzw. von Rauchwolken in der Messelektrode auftreten, kompensiert werden. Durch das Auftreffen des geladenen Rauches von unterschiedlichen Seiten her auf die Elektrode werden ersichtlicherweise Influenzströme entgegengesetzter Polarität erzeugt, die sich auf einfachste Weise in der Elektrode selbst aufheben. Dieses Prinzip lässt sich erfindungsgemäss vervollkommnen, wenn die Elektrode als quer zur Strömungsrichtung elektrisch geschlossener Kreis ausgebildet ist.Compensation can also advantageously be achieved if the measuring electrode is arranged with respect to the air flow in such a way that the air flow sweeps the measuring electrode twice, but from opposite sides ten strikes, or flows through the electrode, so that influence currents, which occur due to net charge of the ambient air passing through or of smoke clouds in the measuring electrode, are compensated for. When the charged smoke hits the electrode from different sides, it is evident that influencing currents of opposite polarity are generated, which are canceled out in the simplest way in the electrode itself. This principle can be perfected according to the invention if the electrode is designed as an electrically closed circle transverse to the direction of flow.

Als Elektrodenanordnung für den erfindungsgemässen Brandmelder eignet sich besonders eine als Gitter ausgebildete Messelektrode und/oder Kompensationselektrode; dies erleichtert die Konvektion und verhindert, dass die im Messraum befindliche Luft bzw. das Gas an Ladungen verarmt. Ausserdem wird sichergestellt, dass vor allem im Zusammenhang mit dem vorstehend beschriebenen Prinzip der Kompensation durch einen Kompensationsraum und/oder zweifaches Durchströmen der Messelektrode einfache Kompensation von Nettoladungs-Einflüssen ermöglicht wird. Dabei lässt sich die Messelektrode auch aus mehreren elektrisch verbundenen Teilelektroden aufbauen, die durch Luft bzw. Gaswolken derart durchströmt werden, dass sich die Influenz-Einflüsse durch Nettoladung in den Teilelektroden aufheben.Particularly suitable as an electrode arrangement for the fire detector according to the invention is a measuring electrode and / or compensation electrode designed as a grid; this facilitates convection and prevents the air or gas in the measuring room from becoming depleted of charges. In addition, it is ensured that, especially in connection with the principle of compensation through a compensation space and / or double flow through the measuring electrode described above, simple compensation of net charge influences is made possible. The measuring electrode can also be constructed from a plurality of electrically connected partial electrodes through which air or gas clouds flow in such a way that the influences of influence caused by the net charge in the partial electrodes cancel each other out.

Besonders hervorragende Messergebnisse lassen sich erfindungsgemäss erreichen, wenn die Messelektrode zwischen zwei Gegenelektroden angeordnet ist, wobei die beiden Gegenelektroden an die Gleichspannungsquelle angeschlossen sind und die Messelektrode zwischen den Gegenelektroden vorgesehen und mit dem Eingang der Messanordnung verbunden ist. Dadurch wird erreicht, dass die Felder in den beiden Messräumen zwischen den beiden Gegenelektroden und der Messelektrode symmetrisch zu dieser verlaufen, d.h. also dass auf die Messelektrode von beiden Messräumen her geladene Teilchen gleicher Polarität auftreffen. Dies garantiert insbesondere hohe Empfindlichkeit.Particularly excellent measurement results can be achieved according to the invention if the measuring electrode is arranged between two counter electrodes, the two counter electrodes being connected to the direct voltage source and the measuring electrode being provided between the counter electrodes and being connected to the input of the measuring arrangement. It is thereby achieved that the fields in the two measuring spaces between the two counter electrodes and the measuring electrode run symmetrically to the latter, i.e. in other words, particles of the same polarity charged from both measuring rooms hit the measuring electrode. This guarantees high sensitivity in particular.

Die Messelektrode wird an den Eingang der Messanordnung angeschlossen und ist damit virtuell auf dem Potential der anderen Seite der Messanordnung. Sie lässt sich vorteilhaft mittels Isolationselementen mit einem Elektrodengehäuse und/oder den Gegenelektroden mechanisch starr verbinden, wobei die Isolationselemente durch elektrisch leitende Teile unterbrochen sind, die mit der anderen Seite der Messelektrode verbunden sind. Damit wird vermieden, dass Kriechströme an den Isolationselementen mitgemessen werden.The measuring electrode is connected to the input of the measuring arrangement and is therefore virtually at the potential of the other side of the measuring arrangement. It can advantageously be mechanically rigidly connected to an electrode housing and / or the counter electrodes by means of insulation elements, the insulation elements being interrupted by electrically conductive parts which are connected to the other side of the measuring electrode. This prevents leakage currents from being measured on the insulation elements.

Die Erfindung ist im folgenden in Ausführungsbeispielen anhand der Zeichnungen näher erläutert. Es zeigen:

  • Figur 1 die Prinzipdarstellung eines Brandmelders mit den Merkmalen der Erfindung,
  • Figur 2 einen Brandmelder mit einer abgewandelten Elektrode,
  • Figur 3 einen Brandmelder mit einer weiter abgewandelten Elektrode,
  • Figur 4 einen erfindungsgemässen Brandmelder mit zwei Messräumen und Aussenabschirmung,
  • Figur 5 ein abgewandeltes Ausführungsbeispiel einer Messelektrode.
The invention is explained below in exemplary embodiments with reference to the drawings. Show it:
  • FIG. 1 shows the basic illustration of a fire detector with the features of the invention,
  • FIG. 2 shows a fire detector with a modified electrode,
  • FIG. 3 shows a fire detector with a further modified electrode,
  • FIG. 4 shows a fire detector according to the invention with two measuring rooms and external shielding,
  • Figure 5 shows a modified embodiment of a measuring electrode.

Figur 1 zeigt die Prinzipdarstellung eines erfindungsgemässen Brandmelders mit einer Messelektrode 1, einer Gegenelektrode 2, einerschematisch dargestellten Messanordnung 3, die gleichzeitig der Alarmauslösung in bekannter Weise dient,sowleeinerGleichspannungsquelle4. Messelektrode 1 und Gegenelektrode 2 sind mittels Isolationselementen 6 an einem Halter 7 befestigt, der seinerseits mit einer Grundplatte 8 verbunden ist. Der Halter 7 ist elektrisch leitfähig und liegt auf Masse, so dass über die Isolationselemente 6 keine Kriechströme zwischen der Messelektrode 1 und der Gegenelektrode 2 fliessen können, da die Messelektrode über die Messanordnung 3 - jedoch nur virtuell - auf Massepotential liegt. Dies ist im Hinblick auf die äusserst geringen fliessenden Ströme von Vorteil. Der Abstand von Messelektrode 1 und Gegenelektrode 2 beträgt 5 mm, die Spannung der Gleichspannungsquelle 4 beträgt 500 Volt, so dass zwischen den beiden Elektroden 1 und 2 eine Feldstärke von 1000 Volt/cm besteht. Gelangen nun geladene Rauchteilchen in den Messraum 9 zwischen Messelektrode 1 und Gegenelektrode 2, so bewirkt das elektrische Feld eine Bewegung der positiven und negativen Teilchen zu den beiden Elektroden. Diese Ladungsbewegung (Ladungs-Drift) influenziert einen Strom in die Messelektrode 1, der in der Messanordnung 3 gemessen wird. Beim Ausführungsbeispiel sind die Messelektroden 1 und die Gegenelektrode 2 als etwa quadratische Platten mit einer Fläche von je 40 cm2 ausgebildet. Selbstverständlich lässt sich die Fläche der Elektroden je nach Anforderung und gewünschter Empfindlichkeit der Messanordnung ändern, wie dies z.B. auch aus dem Ausführungsbeispiel gemäss Figur 4 hervorgeht. Die Gesamtanordnung ist von einer Abschirmung 5 umgeben, die ebenfalls auf Masse liegt. Dadurch wird nicht nur ein mechanischer Schutz der Anordnung gewährleistet, sondern es werden auch Fehlereinflüsse durch Nettoaufladung einer schematisch angedeuteten Rauchwolke 30 insoweit kompensiert, als Einflüsse aus der Ladungswolke ausserhalb der Abschirmung 5 von der Messelektrode 1 ferngehalten werden und dadurch keine Influenzströme entstehen können.Figure 1 shows the basic illustration of a fire detector according to the invention with a measuring electrode 1, a counter electrode 2, a schematically illustrated measuring arrangement 3, which at the same time serves to trigger the alarm in a known manner, and its DC voltage source 4. Measuring electrode 1 and counter electrode 2 are fastened by means of insulation elements 6 to a holder 7, which in turn is connected to a base plate 8. The holder 7 is electrically conductive and is grounded, so that no leakage currents can flow between the measuring electrode 1 and the counterelectrode 2 via the insulation elements 6, since the measuring electrode is - but only virtually - at ground potential via the measuring arrangement 3. This is advantageous in view of the extremely low flowing currents. The distance between the measuring electrode 1 and counter electrode 2 is 5 mm, the voltage of the direct voltage source 4 is 500 volts, so that there is a field strength of 1000 volts / cm between the two electrodes 1 and 2. If now charged smoke particles get into the measuring space 9 between the measuring electrode 1 and the counter electrode 2, the electric field causes the positive and negative particles to move to the two electrodes. This charge movement (charge drift) influences a current into the measuring electrode 1, which is measured in the measuring arrangement 3. In the exemplary embodiment, the measuring electrodes 1 and the counter electrode 2 are designed as approximately square plates with an area of 40 cm 2 each. Of course, the area of the electrodes can be changed depending on the requirement and the desired sensitivity of the measuring arrangement, as can also be seen, for example, from the exemplary embodiment according to FIG. The overall arrangement is surrounded by a shield 5, which is also grounded. This not only ensures mechanical protection of the arrangement, but also influences of errors due to net charging of a schematically indicated smoke cloud 30 are compensated to the extent that influences from the charge cloud outside the shield 5 are kept away from the measuring electrode 1 and thus no influence currents can arise.

Wie schematisch dargestellt, ist sowohl die Messelektrode 1 als auch die Gegenelektrode 2 mit einer Vielzahl von Löchern 11 versehen, welche den Rauch allein aufgrund der Konvektion sowohl aus horizontaler Richtung als auch aus vertikaler Richtung kommend durch den Messraum 9 strömen lassen.As shown schematically, both the measuring electrode 1 and the counter electrode 2 are provided with a multiplicity of holes 11, which allow the smoke to flow through the measuring space 9 coming from the horizontal direction as well as from the vertical direction solely due to the convection.

Figur 2 zeigt eine Anordnung, bei der die Grundplatte 8 als Kompensationselektrode parallel und im gleichen Abstand wie die Gegenelektrode 2 zur Messelektrode 1 angeordnet ist. Grundplatte 8, Messelektrode 1 und Gegenelektrode 2 sind (teilweise nicht dargestellt) jeweils als Lochblech ausgebildet. Durch die Anordnung strömende Gaswolken mit Nettoladung werden zunächst nach aussen durch die Abschirmung 5 abgeschirmt. Ausserdem befindet sich im Messraum 9 und im Kompensationsraum 10 jeweils etwa die gleiche Menge durchströmenden Gases, wodurch die Influenz durch Nettoladung betragsmässig etwa gleich ist. Da sich jedoch in Pfeilrichtung durchströmendes Gas im Messraum 9 auf die Messelektrode 1 zubewegt, im Kompensationsraum 10 jedoch von der Messelektrode 1 wegbewegt, weisen die daraus resultierenden Influenzströme jeweils entgegengesetzte Polarität auf, so dass die Einflüsse durch Nettoladung kompensiert werden.Figure 2 shows an arrangement in which the base plate 8 is arranged as a compensation electrode in parallel and at the same distance as the counter electrode 2 to the measuring electrode 1. Base plate 8, measuring electrode 1 and counter electrode 2 are (part not shown) each formed as a perforated plate. Due to the arrangement, flowing gas clouds with a net charge are initially shielded from the outside by the shield 5. In addition, there is approximately the same amount of gas flowing through each in the measurement space 9 and in the compensation space 10, as a result of which the amount of influence by net charge is approximately the same. However, since gas flowing through in the direction of the arrow moves towards the measuring electrode 1 in the measuring space 9, but moves away from the measuring electrode 1 in the compensation space 10, the resulting influencing currents each have opposite polarity, so that the effects of net charge are compensated for.

Figur 3 zeigt ein Ausführungsbeispiel, bei welchem zwei Gegenelektroden 2 eine Messelektrode 1 zwischen sich einschliessen und dadurch zwei Messräume 9 und 9' begrenzen. Die Gegenelektroden 2 sind als Lochblech ausgebildet, liegen auf Masse und dienen gleichzeitig der Abschirmung der Anordnung nach aussen. Die Befestigung der Messelektrode 1 an der Grundplatte 8 erfolgt durch eine nicht dargestellte Isolator-Anordnung. Da beide Gegenelektroden 2 in bezug auf die Messelektrode 1 auf gleichem Potential liegen, ist die Feldverteilung symmetrisch, d.h., dass sowohl im Messraum 9 als auch im Messraum 9' Ionen negativer Polarität auf die Messelektrode 1 zudriften und der daraus resultierende Influenzstrom in der Messanordnung 3 ermittelt werden kann. Die Empfindlichkeit der Anordnung ist aufgrund der beiden Messräume 9 und 9' erhöht. Ausserdem ist Kompensation von Nettoladungs-Einflüssen durch die Symmetrie der Anordnung gewährleistet.FIG. 3 shows an exemplary embodiment in which two counter electrodes 2 enclose a measuring electrode 1 between them and thereby delimit two measuring spaces 9 and 9 '. The counter electrodes 2 are designed as perforated plates, lie on ground and at the same time serve to shield the arrangement from the outside. The measuring electrode 1 is fastened to the base plate 8 by an insulator arrangement, not shown. Since both counter electrodes 2 are at the same potential with respect to the measuring electrode 1, the field distribution is symmetrical, i.e. that both in the measuring space 9 and in the measuring space 9 ′, ions of negative polarity drift onto the measuring electrode 1 and the resulting influent current in the measuring arrangement 3 can be determined. The sensitivity of the arrangement is increased due to the two measuring rooms 9 and 9 '. In addition, compensation of net charge influences is ensured by the symmetry of the arrangement.

Figur 4 zeigt eine Anordnung, bei welcher eine zylindrische, symmetrische Ausbildung sämtlicher Teile, d.h. der Abschirmung 5, der Messelektrode 1 und der Gegenelektroden 2 vorgesehen ist. Die äussere der beiden Gegenelektroden 2 ist mittels Bolzen 12 aus Isolationsmaterial an der Abschirmung 5 befestigt. Die Messelektrode 1 sowie die zweite Gegenelektrode 2 sind mittels ebenfalls bolzenartig ausgebildeten Isolationselementen 13a, 13b mechanisch miteinander verbunden. Zwischen den Isolationselementen 13a und 13b ist jeweils eine Metallscheibe 14 angeordnet, die auf Masse liegt. Damit werden Kriechströme zwischen den Gegenelektroden 2 und der Messelektrode 1 vermieden. Die zylindrische Ausbildung der Gegenelektrode 2 mit einem Bodenblech 2a, die auch der Ausbildung der anderen Gegenelektrode 2 bzw. der Messelektrode 1 und der Abschirmung 5 entspricht, ist im oberen Abschnitt von Figur 4 schematisch dargestellt.Figure 4 shows an arrangement in which a cylindrical, symmetrical design of all parts, i.e. the shield 5, the measuring electrode 1 and the counter electrodes 2 is provided. The outer of the two counter electrodes 2 is fastened to the shield 5 by means of bolts 12 made of insulation material. The measuring electrode 1 and the second counter electrode 2 are mechanically connected to one another by means of insulation elements 13a, 13b, which are also bolt-shaped. A metal disk 14 is arranged between the insulation elements 13a and 13b, which lies on ground. Leakage currents between the counter electrodes 2 and the measuring electrode 1 are thus avoided. The cylindrical configuration of the counter electrode 2 with a base plate 2a, which also corresponds to the configuration of the other counter electrode 2 or the measuring electrode 1 and the shield 5, is shown schematically in the upper section of FIG. 4.

Diese Anordnung hat zudem noch den Vorteil, dass die lsolationselemente nicht direkt dem Luftstrom ausgesetzt und dadurch vor Verschmutzung geschützt sind.This arrangement also has the advantage that the insulation elements are not directly exposed to the air flow and are therefore protected against contamination.

Eine in Pfeilrichtung durch die Anordnung strömende Gaswolke mit aufgeladenen Rauchpartikeln trifft einmal von rechts kommend auf die Aussenseite der Messelektrode 1 (bei A) und vor dem Verlassen der Anordnung auf die Innenseite der Messelektrode 1 (bei B) auf. Da die Messelektrode 1 zylindrisch ausgebildet ist und einen geschlossenen Stromkreis darstellt, werden dementsprechend Influenzströme durch Nettoladung entgegengesetzte Polarität aufweisen und automatisch kompensiert.A gas cloud with charged smoke particles flowing through the arrangement in the direction of the arrow strikes the outside of the measuring electrode 1 (at A) coming from the right and the inside of the measuring electrode 1 (at B) before leaving the arrangement. Since the measuring electrode 1 is cylindrical and constitutes a closed circuit, influence currents due to net charge will accordingly have opposite polarity and will be automatically compensated.

Ersichtlicherweise besteht auch zwischen der Abschirmung 5, die ebenfalls als Lochblech ausgebildet ist, und der äusseren Gegenelektrode 2 ein elektrisches Feld. Abschirmung 5 und Gegenelektrode 2 begrenzen damit einen kreisringförmigen Kompensationsraum 14, der allerdings aufgrund des grösseren Abstandes kleinere Feldstärke aufweist als die beiden Messräume 9 bzw. 9'. Im Kompensationsraum 14 werden deshalb kleine, langsam strömende geladene Teilchen bereits abgeschieden, bevor sie in den Messraum 9 bzw. 9' gelangen. Dies bewirkt eine grössenselektive Vorabscheidung, die zur Reduktion von Fehlalarmen von grossem Vorteil sein kann.Obviously, there is also an electric field between the shield 5, which is also designed as a perforated plate, and the outer counter electrode 2. Shield 5 and counter electrode 2 thus delimit an annular compensation space 14, which, however, has a smaller field strength than the two measurement spaces 9 and 9 'due to the greater distance. Small, slowly flowing charged particles are therefore already separated in the compensation space 14 before they reach the measurement space 9 or 9 '. This results in a size-selective pre-separation, which can be of great advantage to reduce false alarms.

Figur 5 zeigt ein Ausführungsbeispiel einer Messelektrode, die aus einer Mehrzahl von ausgestanzten Blechstreifen 15 besteht, die mittels einer elektrisch leitfähigen Schiene 16 miteinander verbunden sind.FIG. 5 shows an exemplary embodiment of a measuring electrode which consists of a plurality of punched-out sheet metal strips 15 which are connected to one another by means of an electrically conductive rail 16.

Claims (18)

1. A fire detector with at least two electrodes (1, 2) between which an electric field is produced by a DC voltage source (4), whereby the surfaces of the electrodes which face each other limit a measuring chamber through which the air of a space to be supervised which moves by convection may circulate, one of the electrodes being arranged as a measuring electrode and the other electrode as a counter-electrode, at least one of the electrodes (1,2) being provided with circulation openings (11) for the ambient air to be supervised and/or consisting of a plurality of such partial electrodes (15) with interspaces, the ambient air streaming through these interspaces in the measuring chamber (9, 9a), characterized in that it is provided a current measuring device and evaluation circuit (3), in that the fire detector further comprises a compensation electrode (5, 8) which limits a compensation chamber and which serves as a screening element of the arrangement of electrodes (1, 2) comprising the measuring electrode and the counter-electrode, in that the DC voltage source (4) is connected on the one hand directly or indirectly with the counter-electrode (2) and on the other hand with the current measuring device (3) and in that the measuring electrode (1) is connected to the input of the current measuring device without direct connection with the DC voltage source (4).
2. A fire detector according to claim 1, characterized in that the DC voltage source (4) and the distance between the electrodes are so designed that the electric field intensity at least in part of the measuring chamber is at least of 100 Volt per centimeter.
3. A fire detector according to claim 1 and 2, characterized in that the distance between the electrodes is smaller than 10 mm and greater than 1 mm.
4. A fire detector according to one of the preceding claims, characterized in that said measuring device is a mechanical electroscope (3).
5. A fire detector according to one of the claims 1 to 3, characterized in that said measuring device is an electronic amplifier.
6. A fire detector according to claim 1, characterized in that the compensation chamber (10) is arranged at about the same distance to the measuring electrode (1) as the measuring chamber (9) and in that it may accept about the same volume of the streaming ambient air.
7. A fire detector according to one of the preceding claims, characterized in that the measuring electrode (1) is arranged with respect to the flow of air in such a manner that the flow of air impacts, respectively streams two times through the measuring electrode, the first time from one side and the second time from the opposite side so that induced currents which are caused in the measuring electrode (1) by the net charge of the penetrating ambient air, respectively by clouds of smoke are compensated.
8. A fire detector according to claim 6, characterized in that the measuring electrode, respectively the measuring electrodes are arranged as closed electric circuit transversely to the streaming direction.
9. An electrode arrangement for a fire detector according to one of the preceding claims, characterized in that the measuring electrode(s) (1) and/ or the counter-electrode(s) (2) and/or the compensation electrode(s) are in form of grids.
10. An electrode arrangement for a fire detector according to one of the preceding claims, characterized in that the measuring electrode (1) and/or the counter-electrode (2) are transparent for the flow of air or gas moving by convection.
11. An electrode arrangement according to claim 9 or 10, characterized in that means are provided for guiding the penetrating flow of air, respectively of gas in such a manner and/or the measuring electrode is so designed that the flow of air, respectively of gas impacts, respectively streams through at least two times the measuring electrode at different places, one time at the front side and one time at the back side of said electrode.
12. An electrode arrangement according to claim 11, characterized in that the measuring electrode (1) is comprised of at least two partial electrodes (1) which are penetrated, respectively into which the flow of air or of gas is amitted from opposite sides.
13. An electrode arrangement according to one of the preceding claims, characterized in that the measuring electrode (1) is disposed between two counter-electrodes (2), whereby the two counter-electrodes are connected to the DC voltage source (4) and the measuring electrode to the input of the measuring device.
14. An electrode arrangement according to claim 13, characterized in that both counter-electrodes (2) are set to the same potential.
15. An electrode arrangement according to claim 13, characterized in that the measuring device (3) is connected on the one hand with the measuring electrode (1) and on the other hand with the other potential of the DC voltage source (4).
16. An electrode arrangement according to one of the preceding claims, characterized in that the measuring electrode (1) is connected by means of insulating elements (6, 13, 13a) to an electrode case (ground plate 8) and/or to the counter-electrode (2), the insulating element being interrupted by conductive parts (support 7, metal plates 14) which are connected to the side of the measuring device which is not connected to the measuring electrode.
17. An electrode arrangement according to one of the preceding claims, characterized in that the measuring electrodes (1, 15) and the counter-electrodes (2) are designed as stream transparent bodies and are arranged one inside the other, whereby in the region of the measuring chamber (9, 9a) about a constant distance between the measuring electrodes and the counter electrodes is provided.
18. An electrode arrangement according to claim 17, characterized in that the measuring electrodes (1, 15) and the counter-electrodes (2) have a symmetry of rotation.
EP83903778A 1982-12-03 1983-12-02 Fire alarm and electrode device therefor Expired EP0127645B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83903778T ATE38732T1 (en) 1982-12-03 1983-12-02 FIRE ALARM AND RELATED ELECTRODE ASSEMBLY.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH7028/82 1982-12-03
CH7028/82A CH666135A5 (en) 1982-12-03 1982-12-03 FIRE DETECTORS.

Publications (2)

Publication Number Publication Date
EP0127645A1 EP0127645A1 (en) 1984-12-12
EP0127645B1 true EP0127645B1 (en) 1988-11-17

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Application Number Title Priority Date Filing Date
EP83903778A Expired EP0127645B1 (en) 1982-12-03 1983-12-02 Fire alarm and electrode device therefor

Country Status (7)

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US (1) US4652866A (en)
EP (1) EP0127645B1 (en)
JP (1) JPS60500073A (en)
AU (1) AU572517B2 (en)
CH (1) CH666135A5 (en)
DE (1) DE3378505D1 (en)
WO (1) WO1984002215A1 (en)

Families Citing this family (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1267735A (en) * 1986-01-17 1990-04-10 Nohmi Bosai Kogyo Co., Ltd. Ionization type-smoke detector
GB9703024D0 (en) * 1997-02-14 1997-04-02 Council Cent Lab Res Councils Charged particle analysis
US6828794B2 (en) * 2002-10-24 2004-12-07 Cambustion Limited Electrostatic particle measurement
GB0321039D0 (en) * 2003-09-09 2003-10-08 Council Cent Lab Res Councils Ionising particle analyser
US9013316B2 (en) * 2011-07-28 2015-04-21 Finsecur Smoke detector
US9437093B2 (en) 2011-10-06 2016-09-06 Microchip Technology Incorporated Differential current measurements to determine ION current in the presence of leakage current
US8847802B2 (en) 2011-10-06 2014-09-30 Microchip Technology Incorporated Microcontroller ADC with a variable sample and hold capacitor
US9252769B2 (en) 2011-10-07 2016-02-02 Microchip Technology Incorporated Microcontroller with optimized ADC controller
US9467141B2 (en) 2011-10-07 2016-10-11 Microchip Technology Incorporated Measuring capacitance of a capacitive sensor with a microcontroller having an analog output for driving a guard ring
US9071264B2 (en) 2011-10-06 2015-06-30 Microchip Technology Incorporated Microcontroller with sequencer driven analog-to-digital converter
US9257980B2 (en) 2011-10-06 2016-02-09 Microchip Technology Incorporated Measuring capacitance of a capacitive sensor with a microcontroller having digital outputs for driving a guard ring
US9207209B2 (en) 2011-12-14 2015-12-08 Microchip Technology Incorporated Method and apparatus for detecting smoke in an ion chamber
US9189940B2 (en) 2011-12-14 2015-11-17 Microchip Technology Incorporated Method and apparatus for detecting smoke in an ion chamber
US9176088B2 (en) 2011-12-14 2015-11-03 Microchip Technology Incorporated Method and apparatus for detecting smoke in an ion chamber
US9823280B2 (en) 2011-12-21 2017-11-21 Microchip Technology Incorporated Current sensing with internal ADC capacitor
WO2014016473A1 (en) * 2012-07-24 2014-01-30 Finsecur S.A. Smoke detector
US8884771B2 (en) * 2012-08-01 2014-11-11 Microchip Technology Incorporated Smoke detection using change in permittivity of capacitor air dielectric
DE102014019172B4 (en) 2014-12-17 2023-12-07 Elmos Semiconductor Se Device and method for distinguishing between solid objects, cooking fumes and smoke using a compensating optical measuring system
DE102014019773B4 (en) 2014-12-17 2023-12-07 Elmos Semiconductor Se Device and method for distinguishing between solid objects, cooking fumes and smoke using the display of a mobile telephone
RU2596955C1 (en) * 2015-08-13 2016-09-10 Акционерное общество "Научно-производственное предприятие "Радар ммс" Electric induction fire detector

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3262106A (en) * 1963-01-21 1966-07-19 Robert B P Crawford Gaseous hazard detector system and apparatus
IL22673A (en) * 1964-12-27 1968-06-20 Jaffe A Sensitive smoke and fire detector
FR2034800A1 (en) * 1969-03-11 1970-12-18 Eaton Yale & Towne Detecting combustion products in air, for - fire location
US3754219A (en) * 1972-01-03 1973-08-21 Johnson Service Co High impedance gaseous ion sensing and detection system
AU472425B2 (en) * 1972-02-02 1976-05-27 Taisuke Satsutani Measurement ofthe ion content and electric field ofthe atmosphere
US3949390A (en) * 1974-06-05 1976-04-06 Rca Corporation High voltage aerosol detector
US4134111A (en) * 1976-12-16 1979-01-09 N.V. Tools Limited Aerosol detector and method
US4114088A (en) * 1977-02-28 1978-09-12 Cecil Alfred Laws Atmospheric ion density measurement
US4387369A (en) * 1978-10-11 1983-06-07 Johnson Controls, Inc. Broad spectrum charged electric field polar gas sensing and detection system

Also Published As

Publication number Publication date
JPS6356596B2 (en) 1988-11-08
EP0127645A1 (en) 1984-12-12
AU572517B2 (en) 1988-05-12
AU2983784A (en) 1986-01-02
CH666135A5 (en) 1988-06-30
JPS60500073A (en) 1985-01-17
DE3378505D1 (en) 1988-12-22
US4652866A (en) 1987-03-24
WO1984002215A1 (en) 1984-06-07

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