US2994768A - Method and system for the electric determination of aerosols in a gas - Google Patents

Method and system for the electric determination of aerosols in a gas Download PDF

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Publication number
US2994768A
US2994768A US710732A US71073258A US2994768A US 2994768 A US2994768 A US 2994768A US 710732 A US710732 A US 710732A US 71073258 A US71073258 A US 71073258A US 2994768 A US2994768 A US 2994768A
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space
aerosols
gas
current
electrodes
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US710732A
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English (en)
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Derfler Heinrich
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Cerberus G M B H
CERBERUS GmbH
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CERBERUS GmbH
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    • 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
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
    • G01N27/66—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber and measuring current or voltage
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113—Constructional details

Definitions

  • the present invention relates to a method of checking gases for their aerosol content and to a device for the performance of the said method.
  • aerosol shall be deemed to mean particles of sub-microscopic to microscopic magnitude suspended in gases, e.g. in air. Aerosols are produced, by way of example, in many chemical reactions such as most combustion processes. The method and the device according to this invention are, therefore, suitable for the determination of smoke and combustion gases, and in particular for automatic fire alarms.
  • ionization chambers for the electrical control of the composition of gases has long been known. Although one embodiment of the present invention employs an ionization chamber, the invention is distinguished from the known arrangements since a fundamentally different physical process is employed. Owing to the difierent operation, the arrangement and the design of the ionization chamber employed is different from those of conventional use.
  • a further object of the invention is to provide means in a gas discharge device for effecting the occurrence of charged particles of only one polarity in at least a portion of said gas discharge device.
  • FIG. 1 is a schematic view of a known device for the determination of aerosols in a gas
  • FIG. 2 a graph showing the characteristic of the device according to FIG. 1;
  • FIG. 3 a schematic view of a device for the determination of aerosols in a gas according to one embodiment "of the invention for determining aerosols in a gas;
  • FIG. 7 a diagram of a fire alarm device according to the invention.
  • FIG. 8 the structure of the device according to FIG. 7. In order to explain this difference, the processes tak- Ice ing place within an ionization chamber must be discussed in greater detail.
  • curve 8 shows the course of the current I diagrammatically as a function of the voltage V for pure air. If aerosols, i.e. particles much larger than gas molecules, reach the space between plate 1 and 2, the recombination conditions change. Part of the ions accumulate on aerosol particles so that the rate of travel i.e. the velocity of the relative ions is substantially reduced. These heavy ions remain in the gap much longer so that the likelihood of a recombination process is correspondingly greater owing to the extended dwelling time. The increased recombination in the presence of aerosols, therefore, causes a reduction of the ionization flow at unchanged voltages.
  • An example of the connection between current and voltage in the presence of aerosols is shown by curve 9 in FIG. 2.
  • the essential features of the process so far known are, therefore, the presence of ions of both polarities in the measuring space (bipolar ion flow) and an increased likelihood of recombination by accumulation of ions on aerosol particles. against this, a substantially larger alteration of the flow in the presence of aerosols can be obtained in the process according to this invention.
  • the method according to this invention is characterized by the fact that charged particles of a single polarity are introduced at least into a portion of the space delimited by the electrodes, so that a unipolar current will be set up in at least said portion of the space.
  • 1 and 2 are electrodes to which a voltage is applied with the negative pole at electrode 1; 3 designates a radioactive radiation source e.g. a radiocative substance accommodated in a unilaterally open screening container serving as a shield means which ensures that the radiation can reach only the portion 4 of the space defined by the two electrodes 1 and 2.
  • the portion 4 as can be seen in the drawing is smaller than the remaining portion 5 of the space between the electrodes.
  • the portion 4 i.e. the portion which is radiated by the radioactive source is smaller than the remaining portion 5. Ions of either charge are pro quizd in the space 4 and travel in the direction indicated. Part of the negative ions very quickly leave the ionization area 4 and move through the space 5 not under the action of radiation towards the anode 2.
  • the space 5 While ions of both signs travel in the space 4 (bipolar current), the space 5 holds only negative ions (unipolar current) so that a negative space charge is created.
  • the portion 4 of the space therefore serves to deliver charged particles of only one polarity.
  • the particles of the one polarity alter the static field between the electrodes 1 and 2 and, in particular, the electric field strength in the border area between the portions 4 and 5 which deterv If 2,994,768 is p A mines the flowing cur-rent.
  • the resulting field intensity i in the border area naturally depends on the overall voltage V applied to the electrodes 1 and 2, i.e. the higher the voltage the more ions are moved into space 5 from space 4.
  • the connection between current I'and voltage V for pure air is shown as the curve 11 in FIG. 4.
  • FIG. 5 shows a further embodiment of the invention.
  • an electron emitting electrode e.g. a hot cathode 21 which is suppliedby a voltage source 24.
  • an anode 22 Provided opposite this cathode is an anode 22 connected with the said cathode via a voltage source 25 and a current measuring instrument 26.
  • the voltage source 25 is so dimensioned that the flowing ion current is not saturated in the absence of aerosols.
  • aerosols enter the container 23 through its perforations the electrons emitted by the hot cathode 21 accumulate on the aerosols and thus form heavy ions which move towards the anode substantially less rapidly and, therefore, tend towards a condition of equilibrium with lesser currents.
  • a reduction of voltage is, therefore, indicated by the current measuring instrument 26 as a consequence of the entry of aerosols.
  • FIG. 6 shows an embodiment of the arrangement for the performance of the method.
  • the reference numeral 31 indicates a jacket-type electrode which is permeable for aerosols. It may, by way of example, be designed as a fine-mesh screen or it may be provided with perforations.
  • the counterelectrode is designed as a centrally positioned rod 32. Attached to the electrode 31 are shield means in the form of a ring 33 the outside of which is covered with a radioactive substance, so that the portion of egg. jlhooc radiation effective in respect of ionization can become operative only in a portion of the 4 7 space between the electrodes. This space portion, which is in the vicinity of the electrode 31 corresponds with the space portion 4 of the embodiment shown in FIG. 3.
  • the process according to this invention and the device respectively may be employed for a single or continuous measurement or registration of aerosol concentrations.
  • the chamber disclosed may, by way of example, be connected to a voltage source in series with a resistance, the potential variation at the two electrodes being a measure of the aerosol concentration and serving, if desired, to actuate an indicator member. It is evident that the potential variation reaches an optimum when the resistance displays saturation characteristic, i.e. possesses infinite resistance in the operative range.
  • a second ionization chamber may be'employed as a resistance in which radioactive radiation occurs as well.
  • FIG. 7 shows a complete circuit of a fire alarm.
  • the measuring chamber 34 consists of the electrodes 31 and 32 and the radiation source 33 similar to the arrange ment shown in FIG. 6.
  • the chamber 34 is connected in series with the comparator chamber 35 operating in saturation, the latter comprising the cathode 36, 'the anode 37 and the radiation source 38.
  • Arranged parallel with these two ionization chambers is the ionical relay or cold cathode tube 39 with a cathode 40, a control electrode 41 and an anode 42.
  • This arrangement is connected, via the coil of relay 43, to the voltage source 44.
  • the contact of the relay 43 is arranged in the circuit of an alarm system consisting of a battery 16 and a horn 17. If combustion gases enter the ionization chamber 44, the voltage at the control electrode 41 will rise and ignite the cold cathode tube 39. A strong current will then flow through the coil of relay 43 so that the alarm circuit is closed through contact 45.
  • FIG. 8 The structural design of such an arrangement is shown in- FIG. 8.
  • the reference numerals 3042 in FIG. 8 designate the same members as in FIG. 7.
  • Attached to a base 48 is a housing 51 which encloses the ionization chamber 35.
  • Attached to the said base is the cold cathode tube 39 which carries the ionization chamber 35 on the portion projecting from the base 48.
  • the control electrode 41 is arranged on the wall of the ionization chamber 35 facing the cold cathode tube 39 and it projects into the interior of the cold cathode tube 39 A as shown.
  • a contact pin '49 is connected to the cathode 40 and the housing 51, and a contact pin 50 with the anode 42 and the electrode 37 of the ionization chamber 35. The electrode 37 is thus placed in the interior of this chamber 35.
  • the ionization chamber 34 has an outer. electrode 31 designed as a perforated cap which may be attached to the housing 51.
  • the electrode 32 of chamber 34 projects from the outer wall of chamber 35.
  • the radioactive substance 33 is arranged similarly to that disclosed in connection with FIG. 6;
  • means for the alteration of the measuring range may be'provided as well. These means may consist of devices for the geometric alteration of the chamber or in devices for the alteration of the position of the radioactive radiation source, or in an adjustable or interchangeable stop in front of the radiation source.
  • a method for determining the presence of aerosols in a gas comprising the steps of generating an electrostatic field, subjecting said gas to said electrostatic field, injecting ionizing rays into a portion of said electrostatic field to thereby generate charged particles in said portion of said field and efiect the presence of charged particles of only one polarity in said remaining portion of said field, measuring the current flowing in said field, and comparing said current with that flowing through a like electrostatic field in a like gas substantially free from aerosols.
  • a system for determining the presence of aerosols in a gas comprising two electrodes distanced and electrically insulated from each other and defining a space therebetween, a DC. voltage source applied to said electrodes and causing an electrostatic field in said space, means arranged adjacent said space for producing charged particles of one polarity in a predetermined portion of said space and causing a substantial unipolar current in said field, means connected with said electrodes for measuring said unipolar current, means for supplying said gas to said space, said aerosols when present in said gas accumulating to said charged particles of said one polarity and thereby decreasing said unipolar current to thereby afford a determination of the presence of said aerosols in said space by said measuring means.
  • a system for determining the presence of aerosols in a gas comprising two electrodes distanced and electrically insulated from each other and defining a space therebetween, a DO. voltage source applied to said electrodes and causing an electrostatic field in said space, a radioactive substance emitting ionizing rays arranged adjacent to the first of said electrodes to produce charged particles in a first portion of said space, shield means arranged adjacent to said radioactive substance and between said substance and said second electrode to prevent said ionizing rays from reaching the second portion of said space and to thereby efiect a substantially unipolar current in said second portion of said space, means connected with said electrodes for measuring the current caused by said electrostatic field and said charged particles, means for supplying said gas to said space, said aerosols when present in said gas accumulating to said charged particles of said one polarity and thereby decreasing said unipolar current to thereby afiord a determination of the presence of said aerosols in said space by said measuring means.
  • a system for determining the presence of aerosols in a gas comprising two electrodes distanced and electrically insulated from each other and defining a space therebetween, the first electrode being of the jacket type,
  • the second electrode having the form of a rod and being centrally arranged in said first electrode, a DC. voltage source applied to said electrodes and causing an electrostatic field in said space, a ring centrally arranged in and connected with said first electrode, the axial length of said ring being substantially smaller than the axial length of said first electrode, and defining an outer and an inner portion in said space, a radioactive substance emitting ionizing rays being arranged at the outside of said ring, to thereby direct said ionizing rays into said outer portion of said space and to efiect a substantially unipolar current in the inner portion of said space, means connected with said electrodes for measuring the current caused by said electrostatic field and said charged particles, means for supplying said gas to said space, said aerosols when present in said gas accumulating to said charged particles of said one polarity and thereby decreasing said unipolar current to thereby afiord a determination of the presence of said aerosols in said space by said measuring means.
  • a fire alarm device comprising aerosol detecting means including two electrodes distanced and electrically insulated from each other and defining a space therebetween, a DC. voltage source having a negative and a positive pole, a relay and a resistor serially connected with said electrodes, and having junction points therebetween, a radioactive substance emitting ionizing rays arranged adjacent to the first of said electrodes, shield means defining a first and a second portion in said space, said shield means preventing said ionizing rays from reaching the second portion of said space to thereby effect a substantially unipolar current in said second portion of said space, a gas filled tube having a cathode, and anode and a control electrode, said cathode being connected with the negative pole of said D.C.
  • said anode being connected with the junction point between said serially connected resistor and said relay
  • said control electrode being connected with the junction point between said serially connected second electrode and said resistor, means for supplying said gas to said space, said aerosols when present in said gas in a predetermined value decreasing said current as to elfect an ignition of said gas filled tube and thereby actuating said relay.
  • said resistor is an ionization chamber having a radioactive substance emitting ionizing rays.

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  • Chemical & Material Sciences (AREA)
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US710732A 1957-01-25 1958-01-23 Method and system for the electric determination of aerosols in a gas Expired - Lifetime US2994768A (en)

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CH (1) CH346795A (nl)
DE (1) DE1046372B (nl)
FR (1) FR1198450A (nl)
GB (1) GB854594A (nl)
NL (1) NL99411C (nl)

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102200A (en) * 1959-05-29 1963-08-27 Gen Electric Penetrating radiation measurement by ionization of a particle bearing aerosol
US3176135A (en) * 1960-01-26 1965-03-30 Nat Res Dev Apparatus for detecting and analysing low gaseous concentrations
US3185845A (en) * 1961-02-15 1965-05-25 Continental Oil Co Method of and apparatus for analyzing chemical compounds
US3233100A (en) * 1962-01-10 1966-02-01 Cerberus Ag Determining presence of aerosols in gases
US3446958A (en) * 1964-05-08 1969-05-27 Centre Nat Rech Scient Ionization type gauge usable over a wide range of pressures
US3582646A (en) * 1967-02-09 1971-06-01 Vigifeu Aubervilliers Ionization fire detection device
US3935466A (en) * 1968-09-26 1976-01-27 Hochiki Kabushiki Kaisha Smoke detector adapted to a smoke sensing apparatus
US4027165A (en) * 1976-02-17 1977-05-31 The United States Of America As Represented By The United States Energy Research And Development Administration Ionization detection system for aerosols
US4058803A (en) * 1976-02-06 1977-11-15 Cerberus Ag Duplex ionization-type fire sensor
US4168497A (en) * 1976-03-15 1979-09-18 Cerberus Ag Fire and smoke sensing system
US4185196A (en) * 1978-01-13 1980-01-22 General Electric Company Ionization smoke detector having improved stability and sensitivity
USRE30323E (en) * 1968-09-26 1980-07-01 Hochiki Kabushiki Kaisha Smoke detector adapted to a smoke sensing apparatus
US4213047A (en) * 1978-10-25 1980-07-15 General Signal Corporation Smoke detector having unipolar ionization chamber
US4245174A (en) * 1978-04-24 1981-01-13 Isotec Industries Limited Dual ionization chamber
US4362941A (en) * 1981-01-26 1982-12-07 Honeywell Inc. Apparatus and a method for detecting and measuring trace gases in air or other gaseous background

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1133921B (de) * 1960-04-05 1962-07-26 Hans Christoph Siegmann Dipl P Anordnung zur relativen Bestimmung des Staubgehaltes der Luft unter Anwendung einer ein radioaktives Praeparat enthaltenden Ionisationskammer
FR1568048A (nl) * 1968-01-19 1969-05-23
JP4145360B2 (ja) 1997-05-20 2008-09-03 ライカ ミクロスコピー ズュステーメ アーゲー 特に、手術顕微鏡のための台架

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2408051A (en) * 1942-04-04 1946-09-24 American District Telegraph Co Fire and smoke detector and the like
US2594777A (en) * 1950-07-14 1952-04-29 Ionics Ion controller
US2702898A (en) * 1953-10-06 1955-02-22 Electro Watt Electrical And In Gas-responsive control apparatus
US2785312A (en) * 1953-09-21 1957-03-12 Ionaire Inc Ion generator using radioactive material

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2408051A (en) * 1942-04-04 1946-09-24 American District Telegraph Co Fire and smoke detector and the like
US2594777A (en) * 1950-07-14 1952-04-29 Ionics Ion controller
US2785312A (en) * 1953-09-21 1957-03-12 Ionaire Inc Ion generator using radioactive material
US2702898A (en) * 1953-10-06 1955-02-22 Electro Watt Electrical And In Gas-responsive control apparatus

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102200A (en) * 1959-05-29 1963-08-27 Gen Electric Penetrating radiation measurement by ionization of a particle bearing aerosol
US3176135A (en) * 1960-01-26 1965-03-30 Nat Res Dev Apparatus for detecting and analysing low gaseous concentrations
US3185845A (en) * 1961-02-15 1965-05-25 Continental Oil Co Method of and apparatus for analyzing chemical compounds
US3233100A (en) * 1962-01-10 1966-02-01 Cerberus Ag Determining presence of aerosols in gases
US3446958A (en) * 1964-05-08 1969-05-27 Centre Nat Rech Scient Ionization type gauge usable over a wide range of pressures
US3582646A (en) * 1967-02-09 1971-06-01 Vigifeu Aubervilliers Ionization fire detection device
US3935466A (en) * 1968-09-26 1976-01-27 Hochiki Kabushiki Kaisha Smoke detector adapted to a smoke sensing apparatus
USRE30323E (en) * 1968-09-26 1980-07-01 Hochiki Kabushiki Kaisha Smoke detector adapted to a smoke sensing apparatus
US4058803A (en) * 1976-02-06 1977-11-15 Cerberus Ag Duplex ionization-type fire sensor
US4027165A (en) * 1976-02-17 1977-05-31 The United States Of America As Represented By The United States Energy Research And Development Administration Ionization detection system for aerosols
US4168497A (en) * 1976-03-15 1979-09-18 Cerberus Ag Fire and smoke sensing system
US4185196A (en) * 1978-01-13 1980-01-22 General Electric Company Ionization smoke detector having improved stability and sensitivity
US4245174A (en) * 1978-04-24 1981-01-13 Isotec Industries Limited Dual ionization chamber
US4213047A (en) * 1978-10-25 1980-07-15 General Signal Corporation Smoke detector having unipolar ionization chamber
US4362941A (en) * 1981-01-26 1982-12-07 Honeywell Inc. Apparatus and a method for detecting and measuring trace gases in air or other gaseous background

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Publication number Publication date
CH346795A (de) 1960-05-31
GB854594A (en) 1960-11-23
FR1198450A (fr) 1959-12-07
NL99411C (nl)
DE1046372B (de) 1958-12-11

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