EP0248957A1 - Selbsttest-Verbrennungsproduktdetektor - Google Patents

Selbsttest-Verbrennungsproduktdetektor Download PDF

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Publication number
EP0248957A1
EP0248957A1 EP86304538A EP86304538A EP0248957A1 EP 0248957 A1 EP0248957 A1 EP 0248957A1 EP 86304538 A EP86304538 A EP 86304538A EP 86304538 A EP86304538 A EP 86304538A EP 0248957 A1 EP0248957 A1 EP 0248957A1
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EP
European Patent Office
Prior art keywords
combustion products
sensor
test
sensitivity
alarm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP86304538A
Other languages
English (en)
French (fr)
Inventor
Stephen L. Siegel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pittway Corp
Original Assignee
Pittway Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to US06/483,859 priority Critical patent/US4595914A/en
Application filed by Pittway Corp filed Critical Pittway Corp
Priority to EP86304538A priority patent/EP0248957A1/de
Publication of EP0248957A1 publication Critical patent/EP0248957A1/de
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/20—Calibration, including self-calibrating arrangements
    • 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
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/12—Checking intermittently signalling or alarm systems
    • G08B29/14—Checking intermittently signalling or alarm systems checking the detection circuits
    • G08B29/145—Checking intermittently signalling or alarm systems checking the detection circuits of fire detection circuits

Definitions

  • the present invention relates to combustion prod­ucts detectors and, in particular, to means for testing the sensitivity of such detectors.
  • Devices for detecting combustion products are principally of two types, viz., ionization-­type detectors and photoelectric detectors.
  • the princi­ples of the present invention are applicable to any type of combustion products detector, although the pre­ferred embodiment is described in connection with an ionization-type detector.
  • the senor is typ­ically an active ionization chamber which is relatively open to ambient air.
  • a reference impedance is typical­ly provided by a reference ionization chamber which is relatively closed to ambient air, a reference chamber which is open to ambient air but insensitive to prod­ucts of combustion, or a physical resistor.
  • Each of the chambers includes a pair of spaced electrodes, or the chambers may share a common electrode therebetween, and means are provided, such as a source of radioactive energy, for ionizing air molecules between the elec­trodes.
  • the voltage at the sensing elec­trode is monitored by a detection circuit and when it exceeds a preselected alarm level, the detection cir­cuit energizes a suitable alarm circuit.
  • a detection circuit In self-­contained, i.e., battery-powered, combustion products detectors of this type, it is known to provide a bat­tery monitoring circuit which will cause a low battery signal to be generated when the battery has been deplet­ed to near a level at which successful operation of the alarm circuit is no longer assured.
  • this test means may comprise a manually-operated switch for connection an impedance across the ionization chambers, thereby to change the voltage thereacross so that the sensing electrode volt­age is equal to that which would be produced if combus­tion products were present in an amount beyond which the generation of an alarm is necessary.
  • Such arrange­ments are disclosed, for example, in U.S. Patents No. 4,097,850 and 4,246,572. These test devices simply check to see if the sensitivity of the sensor is above a predetermined minimum sensitivity. But it is important that the sensitivity not be too high, so as to avoid frequent false alarms. No prior test devices are concerned with the maximum sensitivity of the sensor.
  • An important object of this invention is the provi­sion of a combustion products detector which includes means for testing to determine whether the sensitivity of the sensor is below a predetermined maximum sensitivity.
  • Still another object of this invention is the pro­vision of a combustion products detector of the type set forth, which includes means for testing whether the sensitivity of the sensor is in a predetermined range between the minimum and maximum sensitivities.
  • a combustion products detector hav­ing a sensor for producing an output signal in response to the presence of an amount of combustion products in excess of a threshold amount, wherein the threshold amount varies inversely with the sensitivity of the sen­sor, and wherein the desired sensitivity is in a prede­termined range between minimum and maximum sensitivities
  • the improvement comprising: test means for simulating the presence of combustion products in an amount slightly less than the amount corresponding to the maximum sensitivity, test means for simulating the presence of combustion products in an amount slight­ly greater than the amount corresponding to the minimum sensitivity, control means for actuating the test means, and alarm means coupled to the sensor and responsive to an output signal therefrom for producing an alarm indication, whereby an alarm indication is pro­ prised in response to actuation of the test means when the sensitivity of the sensor exceeds the maximum sensi­tivity or when the sensitivity of the sensor is less than the minimum sensitivity.
  • the detector 10 includes circuitry, which is con­nected to a sensor 12 of the ionization type.
  • the sensor 12 includes a reference ionization chamber 13 having an electrode 14 connected to a positive battery supply voltage (B+) and an electrode 15, which are main­tained in a spaced relationship by a spacer (not shown) of insulating material, the electrodes 14 and 15 and the spacer together forming a relatively imperforate closure.
  • the sensor 12 also includes an active ioniza­tion chamber 16 which has an electrode 17 which may be in the form of a relatively perforate conductive hous­ing cooperating with the electrode 15 to define the ac­tive ionization chamber 16, the electrode 15 being common to both chambers 13 and 16.
  • Means are provided, such as a radioactive source (not shown) for ionizing air molecules within both of the chambers, whereby with a voltage applied across the electrodes 14 and 17 an electric field is generated within each chamber to establish a current flow there-­through by movement of the ions between the electrodes in a well known manner.
  • the reference and active cham­bers 13 and 16 thus form a voltage divider and they are connected in series with a resistor 18 between the B+ supply and ground.
  • the voltage at the electrode 15 is a function of the relative impedances of the cham­bers 13 and 16.
  • Resistor 18 is much lower in impedance than the ionization chambers and will therefore normal­ly not influence the sensing electrode voltage value.
  • the combustion products detector 10 also includes a potentiometer 21 connected across the B+ supply and having a wiper which is connected to the reference ter­minal of a smoke comparator 22, the other terminal of the comparator 22 being connected to the sensor elec­trode 15.
  • the output of the comparator 22 is connected to one of three inputs of an OR gate 23, the output of which is connected to the input of a horn driver 24, the output of which is connected to an output terminal 25 to which may be connected a suitable horn (not shown).
  • the horn driver 24 may be a single driver to activate an associated electromechanical horn or multi­ple drivers to operate a piezoelectric horn. It will be appreciated that other types of annunciators could also be provided.
  • the combustion products detector 10 also includes a low battery comparator 26 having a reference input terminal which is connected to an internal reference voltage provided by a current source 27 connected to the B+ supply, the reference voltage being regulated by a Zener diode 28.
  • the anode of the Zener diode 28 is connected to the negative terminal of a battery 29, the positive terminal of which is the B+ supply and is connected to the other input terminal of the comparator 26.
  • the output of the low battery comparator 26 is con­ nected to one of two inputs of an AND gate 31, the out­put of which is connected to one of the inputs of the OR gate 23.
  • the other input of the AND gate 31 is con­nected to the output line 1 of a clock 32, which output is also connected to the reset terminals of two D-type flip-flops 33 and 34, the set terminals of which are connected to ground.
  • the data inputs of the flip-flops 33 and 34 are connected to the output of the smoke com­parator 22, while the clock inputs of the flip-flops 33 and 34 are respectively connected to output lines 3 and 4 of the clock 32.
  • the clock 32 also has an output line 2 which is connected to an inhibit terminal of the horn driver 24 and is also connected through an amplifier 35 to the gate of a metal oxide semiconductor field-effect tran­sistor ("MOSFET") switch 36, the drain of which is con­nected to the electrode 17 of the sensor 12.
  • MOSFET metal oxide semiconductor field-effect tran­sistor
  • Connected in series between the source of the transistor 36 and the B+ supply are two resistors 37 and 38.
  • the resis­tor 38 is connected across the source and drain of a MOSFET 39, the gate of which is connected to the output of an inverter amplifier 40, the input of which is con­nected to an output line 4 of the clock 32.
  • the clock 32 also has an output line 5 which is connected to one input of an AND gate 41, the other input of which is connected to the output of an OR gate 42 having two input terminals which are respectively connected to the Q output of the flip-flop 33 and the inverted Q output of the flip-flop 34.
  • the output terminal of the AND gate 41 is connect­ed to the other input terminal of the OR gate 23.
  • the operation of the combustion products detec­tor 10 will be described.
  • the impedance of the ac­tive ionization chamber 16 will increase.
  • an output will be produced from the smoke comparator 22, which is transmitted through the OR gate 23 to activate the horn driver 24.
  • the associ­ated horn (not shown) will remain activated as long as the amount of combustion products is sufficient to main­tain the voltage of the electrode 15 at or above the ex­ternal reference.
  • the external test switch 20 is closed, thereby connecting the voltage di­vider consisting of resistors 19 and 18 in parallel with the sensor 12. This operates to raise the voltage at the electrode 15 in the same manner as it would be raised by the presence of actual combustion products in an amount sufficient to actuate the alarm. Accordingly, the closure of the test switch 20 acts to simulate the presence of combustion products, raising the voltage of the electrode 15 above the external ref­erence to produce an output from the smoke comparator 22.
  • a low battery comparator 26 for monitoring the B+ supply voltage, and producing a fault signal in the event that the battery voltage drops below a level necessary for proper operation of the combustion products detector 10.
  • a continuous output would be produced from the low battery compar­ator 26.
  • This output signal is applied to one terminal of the AND gate 31, the other input of which is applied from output line 1 of the clock 32.
  • This clock signal is illustrated in FIG. 1, the various waveforms of which are designated by the line numbers corresponding to the output lines of the clock 32.
  • the waveform on line 1 comprises a short pulse 43, typically approximately 10 ms in duration, which is pe­riodically repeated at relatively infrequent intervals, typically about one minute.
  • each clock pulse 43 on line 1 produces an output from the AND gate 31, which is applied through the OR gate 23 to activate the horn driver 24.
  • the combustion products detector 10 will produce a short 10 ms "beep" about once per min­ute. This intermittent signal is easily distinguish­able from the continuous alarm signal which is produced in the presence of combustion products, for unambiguously indicating the low battery condition.
  • the pulse 44 on line 2 is also applied through the amplifier 35 to the gate of the MOSFET 36, turning it on and thereby connecting the voltage divider consisting of resistors 37, 38 and 18 in parallel with the sensor 12. This causes a change in the voltage at the electrode 15 in generally the same manner as was described above in con­ nection with the operation of the manual external test switch 20.
  • this minimum sensi­tivity is such that the sensor will respond to produce a smoke alarm indication when the amount of combustion products reaches 1.5% obscuration per foot (the higher the sensitivity of the sensor 12, the lower the amount of combustion products necessary in order to trigger it into alarm).
  • the combustion products detector 10 will frequently produce false or nuisance alarms (such as in the event of someone smok­ing a cigarette or cooking in the general vicinity of the combustion products detector).
  • the maximum sensi­tivity of the sensor 12 be such that it will not be triggered into alarm by an amount of combustion prod­ucts at .5% obscuration per foot or less.
  • the sensitivity of the sensor 12 be in a range corresponding to amounts of combustion products in the range between .5% and 1.5% obscuration per foot.
  • the values of the resistors 37 and 38 are chosen so that they will cause a change in voltage at the elec­trode 15 slightly less than the minimum needed to cause an output from the smoke comparator 22 to occur.
  • the connection of the resistors 37 and 38 across the sensor 12 simulates an amount of smoke just below the amount corresponding to the maximum sensitiv­ity of the sensor 12, i.e., slightly less than .5% obscuration per foot.
  • the sensitivity of the sensor 12 is in the desired range, it will not respond to this combustion products simulation for producing an output from the smoke comparator 22.
  • sensitivity of the sensor 12 is too high, i.e., the clear-air voltage of the electrode 15 is greater than it should be, the closure of the transistor switch 36 will raise the voltage of the electrode 15 above the external reference and produce an output signal from the smoke comparator 22. This is again applied to the horn driver 24 through the OR gate 23, but the horn driver 24 is not activated since it is being inhibited by the pulse 44 on clock line 2.
  • the output from the smoke comparator 22 is also applied to the data terminals of each of the flip-flops 33 and 34 which were just reset at time t0.
  • the flip-flop 33 now has its set and reset termi­nals at ground or logic low level. In this condition, the Q terminal will be low and can be become high only in the event that there is a logic high at the data termi­nals and a positive-going transition at the clock termi­nal.
  • the clock 32 also produces on line 3 a negative-going pulse 45, of about 1 second duration.
  • the clock 32 Simultaneously with the positive going transition 46 of the pulse 45 at time t2, the clock 32 produces on line 4 a negative going pulse 47, having a duration of about 1 second, which is applied to the inverter am­plifier 40 and to the clock input terminal of the flip-­flop 34.
  • the inverter amplifier 40 produces a high output which is applied to the base of the transistor switch 39, switching it on for shorting the resistor 38.
  • resistor 37 forms a voltage divider with resistor 18 which is connected across the sensor 12. The value of the resistor 37 is selected to cause a change in the voltage at the electrode 15 which will be just in excess of that which would be produced by an amount of smoke corresponding to 1.5% obscuration per foot.
  • connection of the resistor 37 alone, together with resistor 18, across the sensor 12 simulates an amount of smoke just in excess of that corresponding to the minimum permissible sensitivity for the sensor 12. Accordingly, if the sensitivity of the sensor 12 is in the desired range, the voltage at the electrode 15 will be elevated above the external reference and the smoke comparator 22 will produce an output signal. This does not activate the horn driver 24 because it is still inhibited by the pulse 44. The output of the smoke comparator 22 is also applied to the data terminal of the flip-flop 34.
  • the positive going transition 48 of the pulse 47 will cause the in­verted Q output terminal of flip-flop 34 to change state to a logic low level at time t3 (the inverted Q output is normally at a logic high level when the set and reset terminals are at ground level, the inverse of the Q output described previously), so as to not affect the output of the OR gate 42.
  • the inverted Q output will remain at the logic low level until reset at the next clock pulse 43, about 1 minute later.
  • the pulses 44 and 47 both terminate at time t3.
  • the transistor switches 36 and 39 are both opened, disconnecting the resistors 37 and 38 and, simultaneously the inhibit is removed from the horn driver 24.
  • two short (preferably about 10 ms) pulses 49, with 10 ms in between are produced on line 5 of the clock 32 and applied to the AND gate 41.
  • the AND gate 41 will produce two brief high outputs which are applied through the OR gate 23 to activate the horn driver 24 and produce a unique fault indication.
  • the circuitry enclosed in the dashed-line 50 could be an in­tegrated circuit.
  • the test resistors 37 and 38 could alternatively be connected external to the integrated circuit for more precise control, if needed.
  • the self-test circuit 30 could also be utilized for testing the sensitivity of other types of combustion products detectors. In photoelectric detectors, as an example, the light emitter output or light sensor input sensitivity or internal reflective surfaces could be similarly electronically controlled to simulate smoke and accom­ plish similar results.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
EP86304538A 1983-04-11 1986-06-12 Selbsttest-Verbrennungsproduktdetektor Withdrawn EP0248957A1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US06/483,859 US4595914A (en) 1983-04-11 1983-04-11 Self-testing combustion products detector
EP86304538A EP0248957A1 (de) 1986-06-12 1986-06-12 Selbsttest-Verbrennungsproduktdetektor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP86304538A EP0248957A1 (de) 1986-06-12 1986-06-12 Selbsttest-Verbrennungsproduktdetektor

Publications (1)

Publication Number Publication Date
EP0248957A1 true EP0248957A1 (de) 1987-12-16

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EP86304538A Withdrawn EP0248957A1 (de) 1983-04-11 1986-06-12 Selbsttest-Verbrennungsproduktdetektor

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EP (1) EP0248957A1 (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2214307A (en) * 1988-01-04 1989-08-31 Pittway Corp A unit with remote test initiation apparatus
EP0571841A1 (de) * 1992-05-28 1993-12-01 Nohmi Bosai Ltd. Apparat zur Messung der Empfindlichkeit eines Feuerdetektors
EP0618556A1 (de) * 1993-03-31 1994-10-05 Nohmi Bosai Ltd. Photoelektrischer Feuerdetektor
WO1996032705A1 (en) * 1995-04-13 1996-10-17 Digital Security Controls Ltd. Self-diagnostic smoke detector
EP1583055A2 (de) * 2004-03-30 2005-10-05 Nohmi Bosai Ltd. Feuerdetektor und Erfassungssystem von Zustandsinformationen des Feuerdetektors

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097850A (en) * 1976-11-01 1978-06-27 Pittway Corporation Means for adjusting and for testing a detecting device
EP0122489B1 (de) * 1983-04-08 1988-06-01 Nohmi Bosai Kogyo Co., Ltd. Einrichtung zum Testen der Funktion eines photoelektrischen Rauchdetektors
EP0113461B1 (de) * 1982-12-14 1989-08-02 Nohmi Bosai Kogyo Co., Ltd. Funktionelle Prüfungsmittel eines Rauchdetektors nach dem Streulichtprinzip

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097850A (en) * 1976-11-01 1978-06-27 Pittway Corporation Means for adjusting and for testing a detecting device
EP0113461B1 (de) * 1982-12-14 1989-08-02 Nohmi Bosai Kogyo Co., Ltd. Funktionelle Prüfungsmittel eines Rauchdetektors nach dem Streulichtprinzip
EP0122489B1 (de) * 1983-04-08 1988-06-01 Nohmi Bosai Kogyo Co., Ltd. Einrichtung zum Testen der Funktion eines photoelektrischen Rauchdetektors

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2214307A (en) * 1988-01-04 1989-08-31 Pittway Corp A unit with remote test initiation apparatus
GB2214307B (en) * 1988-01-04 1992-08-26 Pittway Corp A unit with remote test initiation
EP0571841A1 (de) * 1992-05-28 1993-12-01 Nohmi Bosai Ltd. Apparat zur Messung der Empfindlichkeit eines Feuerdetektors
EP0618556A1 (de) * 1993-03-31 1994-10-05 Nohmi Bosai Ltd. Photoelektrischer Feuerdetektor
US5574435A (en) * 1993-03-31 1996-11-12 Nohmi Bosai, Ltd. Photoelectric type fire detector
WO1996032705A1 (en) * 1995-04-13 1996-10-17 Digital Security Controls Ltd. Self-diagnostic smoke detector
EP1583055A2 (de) * 2004-03-30 2005-10-05 Nohmi Bosai Ltd. Feuerdetektor und Erfassungssystem von Zustandsinformationen des Feuerdetektors
EP1583055A3 (de) * 2004-03-30 2006-01-11 Nohmi Bosai Ltd. Feuerdetektor und Erfassungssystem von Zustandsinformationen des Feuerdetektors
US7280039B2 (en) 2004-03-30 2007-10-09 Nohmi Bosai Ltd. Fire sensor and fire sensor status information acquisition system
US7498949B2 (en) 2004-03-30 2009-03-03 Nohmi Bosai Ltd. Fire sensor and fire sensor status information acquisition system
EP2234080A3 (de) * 2004-03-30 2011-02-02 Nohmi Bosai Ltd. Feuerdetektor und Erfassungssystem von Zustandsinformationen des Feuerdetektors

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