US3470551A - Fire and smoke detector - Google Patents

Fire and smoke detector Download PDF

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US3470551A
US3470551A US511100A US3470551DA US3470551A US 3470551 A US3470551 A US 3470551A US 511100 A US511100 A US 511100A US 3470551D A US3470551D A US 3470551DA US 3470551 A US3470551 A US 3470551A
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smoke
fire
instant invention
amplifier
combustion products
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US511100A
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Abram Aubrey Jaffe
Eliahu Nadav
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Yissum Research Development Co of Hebrew University of Jerusalem
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Yissum Research Development Co of Hebrew University of Jerusalem
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/025—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using electrical or electromechanical means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/60—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrostatic variables, e.g. electrographic flaw testing
    • 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
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/12—Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions

Definitions

  • fire detecting apparatus which depend upon detection of the by-products of combustion have included smoke detectors embodying optical measuring apparatus or gas detectors employing chemicals to detect specific gases, such as carbon monoxide or carbon dioxide, usually formed in the combustion process.
  • smoke detectors embodying optical measuring apparatus or gas detectors employing chemicals to detect specific gases, such as carbon monoxide or carbon dioxide, usually formed in the combustion process.
  • gas detectors employing chemicals to detect specific gases, such as carbon monoxide or carbon dioxide, usually formed in the combustion process.
  • More recent fire and smoke detectors which depend upon detection of the by-products of combustion have included ionization chambers having at least one'pair of electrodes spaced therein. Such electrodes have been impressed with a relatively high potential therebetween to establish predetermined conductivity characteristics of the air between the electrodes. Recognizing that the byproducts of combustion may contain ionized molecules or particles, the presence of such ionized particles within the ionization chamber increases the conductivity within the chamber, which increase of conductivity may be detected, amplified and utilized to activate suitable alarm and/or fire fighting equipment.
  • a second ionization chamber which includes a second pair of voltage impressed spaced electrodes to shield the interior of the second chamber against the admission of extraneous ionized air particles.
  • a quantity of radioactive material the radiation of which imparts normal conductivity characteristics to the space between the electrodes.
  • the presence of smoke particles in the chamber impedes the progress of the alpha-radiation from the radioactive material and thereby reduces the amount of ionization of the air produced by such radioactive material.
  • the reduction of conductivity characteristics within the second chamber may be electrically sensed, amplified and utilized to activate suitable alarm and/or fire lighting apparatus.
  • Patented Sept. 30, 1969 An example of the ionization chamber technique of detecting smoke and combustion by-products may be seen in United States Patent 2,4008,05l issued to K. O. Donelian on Sept. 24, 1946.
  • a device such as that shown in the Donelian patent requires at least two ionization chambers, one of which detects an increase in conductivity between spaced electrodes due to the presence of ionized combustion products therebetween, and the second of which detects the influence of smoke particles on the normal conductivity characteristics established between a pair of spaced electrodes by a radioactive material.
  • both ionization chambers require that a relatively high voltage be impressed upon the spaced electrodes located therein; and thirdly, as is well known, the utilization of a radioactive material, especially those which emit alpha-particles, are a potential health hazard.
  • the instant invention is based on an effect which is quite different from the two effects utilized by such prior art devices as the Donelian patent. It is based on the fact that smoke and combustion products from fires carry a net electrical charge. Recognizing the fact that if a net electrical charge approaches an electrical conductor, an induced charge will be established on the surface of such conductor; the presence of smoke and combustion products from tire may be simply detected by the eletcrical observation of such induced charge on a single electrical conductor.
  • the instant invention 4materially simplifies fire detection by electrically detecting the presence of an induced charge on a single conductor.
  • the single electrode of the instant invention may be made of any shape to provide protection for large and/ or irregular areas while the double ionization chambered device of the prior art is relatively complex and, therefore, does not lend itself to various shapes and sizes.
  • 4it is an object of the instant invention to provide a fire and smoke detector, the operation of which is dependent upon the fact that smoke and combustion products from fire carry a net electrical charge which may be sensed and amplified to activate suitable alarm and/or iire lighting apparatus.
  • It is another object of the instant invention to provide apparatus# for detecting smoke and combustion products from fires comprising sensing means for producing a signal indicative of the presence of a net electrical charge carried by smoke and combustion products from fires; rand amplifier means connected to said sensing means for amplitiying said signal.
  • Still'another object of the instant invention is to provide a fire and smoke detector which electrically detects the presence of an induced charge on an electrode, which induced charge has been established by the approach of the net electrical charge carried by smoke and combustion products from fires.
  • Yet another object of the instant invention is to provide a fire and smoke detector the simplicity of which permits great flexibility with respect to size and shape.
  • FIGURE 1 is a somewhat schematic diagram of a fire land smoke detector constructed in accordance with the teachings of the instant invention
  • FIGURE 2 is an electrical circuit diagram of an amplifier which may operate in conjunction with the fire and smoke detector -of the instant invention.
  • FIGURE 3 is an electrical circuit diagram of an -alarm device which may be utilized in conjunction with the amplifier of FIGURE 2.
  • the detector comprises a sensing element 12, which may be any metal electrode (i.e., electrically conducting material), preferably mesh or perforated, and hollow inside.
  • the sensing element 12 may be virtually of any shape, for example, -a long cylinder extending over a number of yards, or alternatively, may comprise a large, fiat box or sheet to give protection over a large area, such as a ceiling or roof. It is to be understood that the flexibility of shape which the simplicity of the instant invention facilitates represents an important feature of the instant invention in that the invention may be suitably adapted to provide adequate fire protection in var-ions sized and/or irregularly shaped rooms or areas.
  • Sensing element 12 is supported by an insulator 13 of good electrical insulating properties, for example, polytetrafiuoroethylene, and is enclosed by a grounded shield 11, the purpose of which is to screen the sensing element ⁇ 1 2 from any external charges or fields while simultaneously allowing the flow of smoke or combustion products from fires to flow readily therethrough.
  • the shield 11 consists of electrically conducting material preferably in the form of wire mesh or perforated sheet. Although grounded shield 11 is shown as a single layer of metal in FIGURE 1, it is to be understood that more effective electrical screening may be obtained by using several layers of such material.
  • the shape of the grounded shield 11 should conform to, but be larger than, the shape of the sensing element 12.
  • the grounded shield 11 would consist of a coaxial cylinder, or series of cylinders, which enclose the sensing element.
  • An electrical connection is made by an insulated lead through 14 which may consist of a coaxial connector of conventional type, to an electronic amplifier 15.
  • amplifier 15 may be of either a voltage sensitive or charge sensitive type. If a charge sensitive amplifier is used the sensing element may be extended up to va limit such that its electrical capacity is approximately equal to the effective input capacity of the amplifier, without serious loss of sensitivity, Alternatively a number of smaller sensing elements may be connected to a single amplifier.
  • the output of amplifier 15 energizes a relay 16 with one or more pairs of electrical contacts 17 therein being controlled by energzation of the relay 16 to operate any desirable alarm device I18 -and/or automatic fire extinguishing apparatus 19.
  • the instant invention may be combined with a sampling system, for example, consisting of a fan and air ducts, to sample lover a large area.
  • a sampling system for example, consisting of a fan and air ducts, to sample lover a large area.
  • amplifier 15 is of a charge sensitive type, (an example of such amplifier being illustrated in FIGURE 2), it will be apparent that the ow of current between the sensing element 12 and ground, will be amplified by amplifier 15 to energize the coil of relay -16 to close one or more pairs of contacts 17 and activate alarm and/or fire lighting apparatus 18 and 19.
  • FIGURES 2 and 3 there is shown a schematic diagram of an amplifier and alarm circuit which may be used in conjunction with the sensing apparatus described above. It is to be understood, however, that the particular amplifier and -alarm unit shown and described is merely presented as an illustrative embodiment of the instant invention and that the instant invention is in no way intended to be limited to such circuitry.
  • sensing element 12 which is surrounded by a grounded shield 11 represents the input to the field effect transistor Q1 of the first stage of the charge sensitive amplifier 15.
  • the output from amplifier 15 represents the input to the alarm unit, the output coil RL1 of which is energized to close multiple contacts 17 to activate the alarm and/or fire lighting equipment.
  • Apparatus for detecting smoke and combustion products comprising an electrical conductor, a surface of which has an induced charge established thereon when approached by the net electrical charge carried by smoke and combustion products;
  • detection means for detecting the creation of said induced charge on said conductor; and shield means surrounding said electrical conductor for screening said electrical conductor from external charges and electric fields while at the same time permitting the flow of smoke and combustion products therethrough.
  • alarm means responsive to said amplifier for signifying the presence of smoke and combustion products within said shield means.
  • said shield means 5 6 comprises at least one layer of perforated conducting 2,815,483 12/ 1957 Kaufman 324-72 material. i 2,820,947 1/ 1958 Gunn 324-72 4.
  • the apparatus Of Claim 3 wherein Sald perforated 2,994,035 7 /1961 Feifel et aL 324 32 XR conducting material is electrically grounded.

Description

Sept. 30, 1969 A A JAFFE ET AL 3,470,551
FIRE AND SMOKE DETECTOR Filed Dec. 2, 1965 A 2 Sheets-Sheet l OOOO O OOOOO @OOO O OOOO OOOOO OOOOO Sept. 30, 1969 A. A. JAFFE ET AL FRE AND vSMOKE DETECTOR United States Patent() 3,470,551 FIRE AND SMKE DETECTOR Abram Aubrey Jaffe and Eliahu Nadav, Jerusalem, Israel, assignors to Yissum Research Development Company, Jerusalem, Israel, a company of Israel Filed Dec. 2, 1965, Ser. No. 511,100 Claims priority, application Israel, Dec. 27, 1964, 2 73 2,6 Int. Cl. G08b 21 00 U.S. Cl. 340-237 4 Claims ABSTRACT F THE DISCLOSURE This invention relates to a tire and smoke detector and more particularly to a lire and smoke detector the operation of which is dependent upon the detection of the net electrical charge carried by smoke and combustion products from tires.
Heretofore, fire detecting apparatus which depend upon detection of the by-products of combustion have included smoke detectors embodying optical measuring apparatus or gas detectors employing chemicals to detect specific gases, such as carbon monoxide or carbon dioxide, usually formed in the combustion process. These prior device have been relatively complicated, as well as unsuitable or unreliable for many applications, and have required considerable supervision and maintenance, such .as the periodic replacement of exhausted chemicals or parts.
More recent fire and smoke detectors which depend upon detection of the by-products of combustion have included ionization chambers having at least one'pair of electrodes spaced therein. Such electrodes have been impressed with a relatively high potential therebetween to establish predetermined conductivity characteristics of the air between the electrodes. Recognizing that the byproducts of combustion may contain ionized molecules or particles, the presence of such ionized particles within the ionization chamber increases the conductivity within the chamber, which increase of conductivity may be detected, amplified and utilized to activate suitable alarm and/or fire fighting equipment. Recognizing also that smoke particles may sometimes occur without ionized air particles or molecules, these more recent iire and smoke detectors have provided a second ionization chamber which includes a second pair of voltage impressed spaced electrodes to shield the interior of the second chamber against the admission of extraneous ionized air particles. Provided within the second chamber is a quantity of radioactive material the radiation of which imparts normal conductivity characteristics to the space between the electrodes. The presence of smoke particles in the chamber impedes the progress of the alpha-radiation from the radioactive material and thereby reduces the amount of ionization of the air produced by such radioactive material. The reduction of conductivity characteristics within the second chamber may be electrically sensed, amplified and utilized to activate suitable alarm and/or lire lighting apparatus.
Patented Sept. 30, 1969 An example of the ionization chamber technique of detecting smoke and combustion by-products may be seen in United States Patent 2,4008,05l issued to K. O. Donelian on Sept. 24, 1946.
'I'he above described prior art re and smoke detectors, as illustrated by the Donelian patent, suffer from several disadvantages which the instant invention effectively eliminates. lSpecifically, a device such as that shown in the Donelian patent requires at least two ionization chambers, one of which detects an increase in conductivity between spaced electrodes due to the presence of ionized combustion products therebetween, and the second of which detects the influence of smoke particles on the normal conductivity characteristics established between a pair of spaced electrodes by a radioactive material. Secondly, both ionization chambers require that a relatively high voltage be impressed upon the spaced electrodes located therein; and thirdly, as is well known, the utilization of a radioactive material, especially those which emit alpha-particles, are a potential health hazard.
In contradistinction thereto, the instant invention is based on an effect which is quite different from the two effects utilized by such prior art devices as the Donelian patent. It is based on the fact that smoke and combustion products from lires carry a net electrical charge. Recognizing the fact that if a net electrical charge approaches an electrical conductor, an induced charge will be established on the surface of such conductor; the presence of smoke and combustion products from tire may be simply detected by the eletcrical observation of such induced charge on a single electrical conductor. Thus, where the prior art detectors, illustrative by the Donelian patent, require separate ionization chambers to detect (1) the presence of ionized combustion products, and (2) the presence of non-ionized smoke particles, the instant invention 4materially simplifies lire detection by electrically detecting the presence of an induced charge on a single conductor.
The advantages derived from the detection of net electrical charge of combustion products may be summarized as follows. A single detector consisting of a single electrode is possible and neither an ionization nor deionization chamber is required. Similarly, where the ionization and the de-ionization chambers of the prior art devices require that relatively high voltages (for example, volts) be impressed upon the spaced apart electrodes located therein, the instant invention requires neither the pairs of electrodes nor the potential impressed thereon. Furthermore, the instant invention completely eliminates the necessity for a radioactive source which, as noted before, presents a potential health hazard in the detectors of the prior art.
As a further advantage, it may be appreciated that the single electrode of the instant invention may be made of any shape to provide protection for large and/ or irregular areas while the double ionization chambered device of the prior art is relatively complex and, therefore, does not lend itself to various shapes and sizes.
Accordingly, 4it is an object of the instant invention to provide a lire and smoke detector, the operation of which is dependent upon the fact that smoke and combustion products from fire carry a net electrical charge which may be sensed and amplified to activate suitable alarm and/or iire lighting apparatus.
It is another object of the instant invention to provide apparatus# for detecting smoke and combustion products from lires comprising sensing means for producing a signal indicative of the presence of a net electrical charge carried by smoke and combustion products from fires; rand amplifier means connected to said sensing means for amplitiying said signal.
It is another object of the instant invention to provide a fire and smoke detector which eliminates the relatively complex arrangements prevalent in the prior art.
Still'another object of the instant invention is to provide a fire and smoke detector which electrically detects the presence of an induced charge on an electrode, which induced charge has been established by the approach of the net electrical charge carried by smoke and combustion products from fires.
Yet another object of the instant invention is to provide a fire and smoke detector the simplicity of which permits great flexibility with respect to size and shape.
Other objects and a fuller understanding of the instant invention may be had by referring to the following specification and drawings, in which:
FIGURE 1 is a somewhat schematic diagram of a fire land smoke detector constructed in accordance with the teachings of the instant invention;
FIGURE 2 is an electrical circuit diagram of an amplifier which may operate in conjunction with the fire and smoke detector -of the instant invention; and
FIGURE 3 is an electrical circuit diagram of an -alarm device which may be utilized in conjunction with the amplifier of FIGURE 2.
Referring to FIGURE 1, there -is shown an illustrative embodiment of the instant invention. The detector comprises a sensing element 12, which may be any metal electrode (i.e., electrically conducting material), preferably mesh or perforated, and hollow inside. The sensing element 12 may be virtually of any shape, for example, -a long cylinder extending over a number of yards, or alternatively, may comprise a large, fiat box or sheet to give protection over a large area, such as a ceiling or roof. It is to be understood that the flexibility of shape which the simplicity of the instant invention facilitates represents an important feature of the instant invention in that the invention may be suitably adapted to provide adequate fire protection in var-ions sized and/or irregularly shaped rooms or areas.
Sensing element 12 is supported by an insulator 13 of good electrical insulating properties, for example, polytetrafiuoroethylene, and is enclosed by a grounded shield 11, the purpose of which is to screen the sensing element `1 2 from any external charges or fields while simultaneously allowing the flow of smoke or combustion products from fires to flow readily therethrough. The shield 11 consists of electrically conducting material preferably in the form of wire mesh or perforated sheet. Although grounded shield 11 is shown as a single layer of metal in FIGURE 1, it is to be understood that more effective electrical screening may be obtained by using several layers of such material.
The shape of the grounded shield =11 should conform to, but be larger than, the shape of the sensing element 12. Thus, if the sensing element 12 were chosen as a long cylinder, the grounded shield 11 would consist of a coaxial cylinder, or series of cylinders, which enclose the sensing element.
An electrical connection is made by an insulated lead through 14 which may consist of a coaxial connector of conventional type, to an electronic amplifier 15. As will be explained in greater detail, amplifier 15 may be of either a voltage sensitive or charge sensitive type. If a charge sensitive amplifier is used the sensing element may be extended up to va limit such that its electrical capacity is approximately equal to the effective input capacity of the amplifier, without serious loss of sensitivity, Alternatively a number of smaller sensing elements may be connected to a single amplifier. The output of amplifier 15 energizes a relay 16 with one or more pairs of electrical contacts 17 therein being controlled by energzation of the relay 16 to operate any desirable alarm device I18 -and/or automatic fire extinguishing apparatus 19.
It is to be understood that the instant invention may be combined with a sampling system, for example, consisting of a fan and air ducts, to sample lover a large area.
The operation of the fire and smoke detector of the instant invention will now be described with respect to FIGURE 1.
Recognizing that smoke and combustion products from fire carry a net electrical charge, the entrance of such combustion products through the perforated, grounded shield 11 and the approach of such products to the immediate vicinity of the sensing element 12, will induce a charge on the surface of sensing element 12. As noted previously, the creation of the induced charge on the surface of sensing element 12 may be observed in changes of electrical potential of the sensing element or by detecting currents flowing from or into such conductor if it is connected to a fixed potential, such as ground. Assuming that amplifier 15 is of a charge sensitive type, (an example of such amplifier being illustrated in FIGURE 2), it will be apparent that the ow of current between the sensing element 12 and ground, will be amplified by amplifier 15 to energize the coil of relay -16 to close one or more pairs of contacts 17 and activate alarm and/or fire lighting apparatus 18 and 19.
Referring to FIGURES 2 and 3, there is shown a schematic diagram of an amplifier and alarm circuit which may be used in conjunction with the sensing apparatus described above. It is to be understood, however, that the particular amplifier and -alarm unit shown and described is merely presented as an illustrative embodiment of the instant invention and that the instant invention is in no way intended to be limited to such circuitry.
Without going into the details of the circuit presented in FIGURE 2 (since all circuit elements have been appropriately identified), it is noted that sensing element 12 which is surrounded by a grounded shield 11 represents the input to the field effect transistor Q1 of the first stage of the charge sensitive amplifier 15. The output from amplifier 15 represents the input to the alarm unit, the output coil RL1 of which is energized to close multiple contacts 17 to activate the alarm and/or fire lighting equipment.
Thus, there has been described a fire and smoke detector, the operation of which is dependent upon the induction of change on a single electrode, which induced charge has been established by the presence of the net electrical charge carried by smoke and combustion products from fires. It is seen that the instant invention represents a significant advancement in terms of simplicity of consturction and operation over prior art devices while at the same time the liexibility inherent in the instant invention lends itself to the maximum protection of large and/or odd-shaped areas.
What is claimed is:
1. Apparatus for detecting smoke and combustion products comprising an electrical conductor, a surface of which has an induced charge established thereon when approached by the net electrical charge carried by smoke and combustion products;
detection means for detecting the creation of said induced charge on said conductor; and shield means surrounding said electrical conductor for screening said electrical conductor from external charges and electric fields while at the same time permitting the flow of smoke and combustion products therethrough.
2. The apparatus of claim 1, lwherein said detecting means includes:
an amplifier for amplifying a signal which represents the establishment of said induced charge on said electrical conductor; and
alarm means responsive to said amplifier for signifying the presence of smoke and combustion products within said shield means.
3. The apparatus of claim 1, wherein said shield means 5 6 comprises at least one layer of perforated conducting 2,815,483 12/ 1957 Kaufman 324-72 material. i 2,820,947 1/ 1958 Gunn 324-72 4. The apparatus Of Claim 3, wherein Sald perforated 2,994,035 7 /1961 Feifel et aL 324 32 XR conducting material is electrically grounded.
References Cited 5 JOHN W. CALDWELL, Pnmary Exammer 2,408,051 9/1946 Donelian 340-237 Us C1 XR. 2,491,445 12/ 1949 Cunningham et al.
2,556,458 l6/1951 Webster. 10 317448'5262
US511100A 1964-12-27 1965-12-02 Fire and smoke detector Expired - Lifetime US3470551A (en)

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IL22673A IL22673A (en) 1964-12-27 1964-12-27 Sensitive smoke and fire detector

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CH (1) CH446961A (en)
DE (1) DE1277711B (en)
FR (1) FR1473061A (en)
GB (1) GB1087609A (en)
IL (1) IL22673A (en)
NL (1) NL6516966A (en)

Cited By (9)

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Publication number Priority date Publication date Assignee Title
US3573777A (en) * 1968-12-09 1971-04-06 Honeywell Inc Combustion products detector control apparatus
US3673586A (en) * 1970-02-19 1972-06-27 Statitrol Corp Resistance controlled timed pulse generator
US3754219A (en) * 1972-01-03 1973-08-21 Johnson Service Co High impedance gaseous ion sensing and detection system
US4360856A (en) * 1981-01-08 1982-11-23 Witthaus Ira L Electric sensor package
WO1984002215A1 (en) * 1982-12-03 1984-06-07 Siegmann Hans Christoph Fire alarm and electrode device therefor
EP0110802A2 (en) 1982-10-04 1984-06-13 Ail Corporation Method and apparatus for indicating an operating characteristic of an internal combustion engine
US6057774A (en) * 1999-01-21 2000-05-02 Brk Brands, Inc. Smoke alarm with anti-dust screen
DE102014019773A1 (en) 2014-12-17 2016-06-23 Elmos Semiconductor Aktiengesellschaft Apparatus and method for distinguishing solid objects, cooking fumes and smoke by means of the display of a mobile telephone
DE102014019172A1 (en) 2014-12-17 2016-06-23 Elmos Semiconductor Aktiengesellschaft Apparatus and method for distinguishing solid objects, cooking fumes and smoke with a compensating optical measuring system

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US4264331A (en) * 1977-08-03 1981-04-28 Johnson Controls, Inc. Charged non-conductive polar gas sensing element and detection system
US4631482A (en) * 1984-10-09 1986-12-23 Auburn International, Inc. Dust flow inducing monitor

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US2408051A (en) * 1942-04-04 1946-09-24 American District Telegraph Co Fire and smoke detector and the like
US2491445A (en) * 1947-02-24 1949-12-13 Shell Dev Flowmeter
US2556458A (en) * 1948-02-09 1951-06-12 W E Anderson Inc Static electricity indicator
US2815483A (en) * 1957-12-03 Electric field detection
US2820947A (en) * 1955-04-29 1958-01-21 Gunn Ross Electric field meter
US2994035A (en) * 1954-12-16 1961-07-25 Feifel Eugen Apparatus for determining the dust content of gases or vapors

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DE901319C (en) * 1938-12-15 1954-01-11 Siemens Ag Changeable electrical capacitor
DE923073C (en) * 1952-03-06 1955-02-03 Lufttechnische Ges M B H Method and device for periodic measurement of the electrical charge in atmospheric air
DE1056008B (en) * 1956-04-06 1959-04-23 Phys Maurice E Nahmias Dr Device for detecting smoke etc.
NL224264A (en) * 1957-10-24
DE1114413B (en) * 1959-06-06 1961-09-28 Telefonbau & Normalzeit Gmbh Electric alarm system

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US2815483A (en) * 1957-12-03 Electric field detection
US2408051A (en) * 1942-04-04 1946-09-24 American District Telegraph Co Fire and smoke detector and the like
US2491445A (en) * 1947-02-24 1949-12-13 Shell Dev Flowmeter
US2556458A (en) * 1948-02-09 1951-06-12 W E Anderson Inc Static electricity indicator
US2994035A (en) * 1954-12-16 1961-07-25 Feifel Eugen Apparatus for determining the dust content of gases or vapors
US2820947A (en) * 1955-04-29 1958-01-21 Gunn Ross Electric field meter

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573777A (en) * 1968-12-09 1971-04-06 Honeywell Inc Combustion products detector control apparatus
US3673586A (en) * 1970-02-19 1972-06-27 Statitrol Corp Resistance controlled timed pulse generator
US3754219A (en) * 1972-01-03 1973-08-21 Johnson Service Co High impedance gaseous ion sensing and detection system
US4360856A (en) * 1981-01-08 1982-11-23 Witthaus Ira L Electric sensor package
EP0110802A2 (en) 1982-10-04 1984-06-13 Ail Corporation Method and apparatus for indicating an operating characteristic of an internal combustion engine
WO1984002215A1 (en) * 1982-12-03 1984-06-07 Siegmann Hans Christoph Fire alarm and electrode device therefor
US6057774A (en) * 1999-01-21 2000-05-02 Brk Brands, Inc. Smoke alarm with anti-dust screen
DE102014019773A1 (en) 2014-12-17 2016-06-23 Elmos Semiconductor Aktiengesellschaft Apparatus and method for distinguishing solid objects, cooking fumes and smoke by means of the display of a mobile telephone
DE102014019172A1 (en) 2014-12-17 2016-06-23 Elmos Semiconductor Aktiengesellschaft Apparatus and method for distinguishing solid objects, cooking fumes and smoke with a compensating optical measuring system

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NL6516966A (en) 1966-03-25
GB1087609A (en) 1967-10-18
FR1473061A (en) 1967-03-17
DE1277711B (en) 1968-09-12
IL22673A (en) 1968-06-20
CH446961A (en) 1967-11-15

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