CA1182592A - Ionization type smoke detector with test circuit - Google Patents
Ionization type smoke detector with test circuitInfo
- Publication number
- CA1182592A CA1182592A CA000393916A CA393916A CA1182592A CA 1182592 A CA1182592 A CA 1182592A CA 000393916 A CA000393916 A CA 000393916A CA 393916 A CA393916 A CA 393916A CA 1182592 A CA1182592 A CA 1182592A
- Authority
- CA
- Canada
- Prior art keywords
- voltage
- electrode
- test
- collector
- switch
- 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.)
- Expired
Links
Classifications
-
- 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
-
- 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
Abstract
ABSTRACT
An ionization detector of the type having a housing with electrodes and a radiation source for causing ion current flow between the electrodes, collector means for detecting, by a change in voltage, a drop in ion current flow, and means responsive to a predetermined change in collector voltage to provide an output signal, in which a test electrode is provided in the housing and means is provided for applying to the test electrode a predetermined voltage of a value that causes said predetermined change in voltage at the collector, whereby said output signal provided when said predetermined voltage is applied to the test electrode if said detector is operating satisfactorily.
An ionization detector of the type having a housing with electrodes and a radiation source for causing ion current flow between the electrodes, collector means for detecting, by a change in voltage, a drop in ion current flow, and means responsive to a predetermined change in collector voltage to provide an output signal, in which a test electrode is provided in the housing and means is provided for applying to the test electrode a predetermined voltage of a value that causes said predetermined change in voltage at the collector, whereby said output signal provided when said predetermined voltage is applied to the test electrode if said detector is operating satisfactorily.
Description
B~CKGROUND OF T~E INVENTION
1 Ionization detectors are desigrled to provide an output signal to actuate o ~ all~rm when smok{! concelltr~tion at t~l~ detector reache~ a prede-lPrmined value, 3 by detec-ti-l~ th~ reduction of ion current in the chamber caused by the pre~ence 4 oi smoke particles. In a single chamber detector, in which the chamber electrodeY
are connected in series with a resistor across a power source, the change in 6 ion current flow change~ the volta~e at the junction between the detector and 7 the resistor. In a two chamber detector, having a detection chamber and a 8 cloaed re~erence chamher connected in series across a power ~ource, the reduction 9 of ion current cauqed by smoke entering the detector chamber changes the voltage at the junction of the chambers. In a dual chamber detector, in which the 11 reference chamber ( or reference volume) ia disposed within the detector 12 chamber with a common ion source, a collector electrode i~ provided in the 13 chamber between the inner und outer electrodes (~ome-times forming the aeparation 14 between the two chambeIs), and the red~ction in ion current ilow chnng~s the voltage on the collector electrode. This change in voltage iB utili~ed to 16 actuate an ala~m.
ge 1 Any of the above systems must be calibrated so that the alarm output signal is provided at a definite predetermined smoke concentration~ This smoke concen-tration provides a particular voltage at the detector, It has been common practice to test such detectors by connecting the reference electrode to ground, or to provide a slowly increasing voltage across the srnoke detecting chamber, and determining the voltage at which the alarm signal is produced. It has also been suggested that a test electrode may be pro-vided in the smoke chamber, to be connected to ground or to a voltage varying device, to cause the alarm test signal.
SUMMARY OF THE INVENTION
In accordance with a particular ernbodiment of the invention, an ionization smoke detector comprises first and second electrodes spaced to define therebe-tween a smoke detecting chamber. The second elec-trode is a collector electrode. An ion source is positioned for emitting radiation into the smoke detecting chamber for causing ionization of a gas therein, and a power supply is connected to the first and second electrodes to establish ion current flow through the srnoke detect-ing chamber. Comparator circuitry is connected to the collector electrode, the collector electrode being adapted to apply a predetermined voltage to the compara-tor circuitry during clean air conditions. ~ first voltage divider network is connected to the power supply and to the comparator circuitry, the first voltage divid-er network generating a reference voltage for application to the comparator circuitry. The reference voltage has a predetermined offset value from the clean air voltage applied to the comparator circuitry by the collector electrode, the comparator circuitry being adapted to generate an alarm signal when the voltage applied to the comparator circuitry by the collector electrode is equal to or less than the reference voltage. A te~t electrode is disposed in the smoke detecting chamber between the first and second electrodes. A second voltage divider network is connected to the power supply circuitry and to the test electrode. Switch means are connected to the second voltage divider network, the switch means having open and closed conditions and being connected to the second voltage divider network such that, when the switch means is in open condition, the voltage applied to the test electrode is the same as the voltage applied to the first electrode by the power supply.
When the switch means is in closed condition, a test voltage is applied to the test electrode, the test voltage on the test electrode being effective to re-duce the voltage on the collector electrode to a value equal to or less than the reference voltage to cause the comparator circuitry to generate an alarm signal~
In accordance with this invention, an ioniza-tion smoke detector may be provided with a test electrode in the detector chamber, and means provided for apply-ing to the test electrode a single predeterrnined voltage,having a value such that it will, in effect, simulate the presence of smoke in the chamber of an amount to which the detector should respond. For example, if it is intended that the detector should produce an alarm signal when the smoke concentration reaches 1% obscura-tion (1% of the light passing through a column of smoke l foot long is absorbed) the presence o-f this concen-tration of smoke causes a certain change in the voltage at -the collector or at the junction, depending on the -type of detector. Therefore the test circuit is designed to apply to the test electrode a voltage of ~ value such that it causes this voltage change to occur at the collec-tor or junction.
- 2b -The test circuit is also designed to apply the test voltage in such a manner that voltage surges that might provide a false indication of satisfactory opera-tion do not occur.
In one embodiment of the invention means is provided for applying the test vol-tage from a remote location.
BRIEF DESCRIPrrION OF ~ ~ FIGUBES OF TlE DRAWING
1 Figure 1 is a schematic view of an ioni~ation detector embodying the
1 Ionization detectors are desigrled to provide an output signal to actuate o ~ all~rm when smok{! concelltr~tion at t~l~ detector reache~ a prede-lPrmined value, 3 by detec-ti-l~ th~ reduction of ion current in the chamber caused by the pre~ence 4 oi smoke particles. In a single chamber detector, in which the chamber electrodeY
are connected in series with a resistor across a power source, the change in 6 ion current flow change~ the volta~e at the junction between the detector and 7 the resistor. In a two chamber detector, having a detection chamber and a 8 cloaed re~erence chamher connected in series across a power ~ource, the reduction 9 of ion current cauqed by smoke entering the detector chamber changes the voltage at the junction of the chambers. In a dual chamber detector, in which the 11 reference chamber ( or reference volume) ia disposed within the detector 12 chamber with a common ion source, a collector electrode i~ provided in the 13 chamber between the inner und outer electrodes (~ome-times forming the aeparation 14 between the two chambeIs), and the red~ction in ion current ilow chnng~s the voltage on the collector electrode. This change in voltage iB utili~ed to 16 actuate an ala~m.
ge 1 Any of the above systems must be calibrated so that the alarm output signal is provided at a definite predetermined smoke concentration~ This smoke concen-tration provides a particular voltage at the detector, It has been common practice to test such detectors by connecting the reference electrode to ground, or to provide a slowly increasing voltage across the srnoke detecting chamber, and determining the voltage at which the alarm signal is produced. It has also been suggested that a test electrode may be pro-vided in the smoke chamber, to be connected to ground or to a voltage varying device, to cause the alarm test signal.
SUMMARY OF THE INVENTION
In accordance with a particular ernbodiment of the invention, an ionization smoke detector comprises first and second electrodes spaced to define therebe-tween a smoke detecting chamber. The second elec-trode is a collector electrode. An ion source is positioned for emitting radiation into the smoke detecting chamber for causing ionization of a gas therein, and a power supply is connected to the first and second electrodes to establish ion current flow through the srnoke detect-ing chamber. Comparator circuitry is connected to the collector electrode, the collector electrode being adapted to apply a predetermined voltage to the compara-tor circuitry during clean air conditions. ~ first voltage divider network is connected to the power supply and to the comparator circuitry, the first voltage divid-er network generating a reference voltage for application to the comparator circuitry. The reference voltage has a predetermined offset value from the clean air voltage applied to the comparator circuitry by the collector electrode, the comparator circuitry being adapted to generate an alarm signal when the voltage applied to the comparator circuitry by the collector electrode is equal to or less than the reference voltage. A te~t electrode is disposed in the smoke detecting chamber between the first and second electrodes. A second voltage divider network is connected to the power supply circuitry and to the test electrode. Switch means are connected to the second voltage divider network, the switch means having open and closed conditions and being connected to the second voltage divider network such that, when the switch means is in open condition, the voltage applied to the test electrode is the same as the voltage applied to the first electrode by the power supply.
When the switch means is in closed condition, a test voltage is applied to the test electrode, the test voltage on the test electrode being effective to re-duce the voltage on the collector electrode to a value equal to or less than the reference voltage to cause the comparator circuitry to generate an alarm signal~
In accordance with this invention, an ioniza-tion smoke detector may be provided with a test electrode in the detector chamber, and means provided for apply-ing to the test electrode a single predeterrnined voltage,having a value such that it will, in effect, simulate the presence of smoke in the chamber of an amount to which the detector should respond. For example, if it is intended that the detector should produce an alarm signal when the smoke concentration reaches 1% obscura-tion (1% of the light passing through a column of smoke l foot long is absorbed) the presence o-f this concen-tration of smoke causes a certain change in the voltage at -the collector or at the junction, depending on the -type of detector. Therefore the test circuit is designed to apply to the test electrode a voltage of ~ value such that it causes this voltage change to occur at the collec-tor or junction.
- 2b -The test circuit is also designed to apply the test voltage in such a manner that voltage surges that might provide a false indication of satisfactory opera-tion do not occur.
In one embodiment of the invention means is provided for applying the test vol-tage from a remote location.
BRIEF DESCRIPrrION OF ~ ~ FIGUBES OF TlE DRAWING
1 Figure 1 is a schematic view of an ioni~ation detector embodying the
2 features o:~ ~he invention, in which the detector is provided with a tes-t ~ electrolie alltl meari~ ~or al~)lyi~ e~ ie~~ ell voltagl to -the test electro~e 4 to simulat- a predl-t(~ led amoun~ of smoke in ~he ch~mber.
Fi~lre _ i.s a Ara~h illllstrating thc relation~hip between -Lhe volta~e on 6 the test elec-trode and the percent smokc which said voltage simulates.
7 Figures 3 and 4 illus-trate modified ~orms of -test circuits which allow the 8 detector to be tes-ted from a remo-te location.
Dl~`SCI~rl'TI~N 1)l` TF~` Il.l,USTRATED EMBOD ~i~TS
Refer~ g to Figllre I of the drawin~ there is i.Llustrated a schema~ic diagrarn of an ioni~ation s~oke detector 10 which comprises a housing 12 ha~ing 11 an inner clectrode 16, an outer electrode 149 and a collector electrode 18.
12 The physical struc-ture of such detectors provides an i~ler or re~erence chamber 1~ 20 between the inner electrode 16 ~nd the collector electrode? and an outer or l/~ smolie detectillg chambel 22 betwcen t~e re~ercllce ellcl.rode arld ~ oul.cr electrode 14. r~c physical struc-tuIe o~ SUCil det,ectors i~ wcll knowrl in th( 1~ art, and are illustrated ill9 for example, U.S. patent 3J935l466 and United 17 Kingdom published application 2~013,39~A. An ioni~atio~ source 24 is provided 18 in the hou~ing to provide ion current flow when the detector i~ connected to a 19 power source p. The outer electrode 14 and the inner electrode 16 are connected across the power source 80 that ion culrent flow of a definite magnitude 21 flows between the inner and outcr electrodes when clean air is in the detector.
22 This ion current flow establishe6 a ~oltage on the collector electrode 23 of predetermined value, which voltage is applied to terminal Tl of a comparator 24 C, to be compared ~i-th a reference voltage established at ter~inal T~ ilom the junction 31 of a voltage divider consisting of resistors R1 and R2 connected 26 in serie~ across the powcr source P~
~Y-55 ?age 3 l ihZ592 1 When smoke enters the chamber, the smoke particles reduce the ion curren-t 2 flow, which reduces the voltage on the collector electrode. ~or example9 in
Fi~lre _ i.s a Ara~h illllstrating thc relation~hip between -Lhe volta~e on 6 the test elec-trode and the percent smokc which said voltage simulates.
7 Figures 3 and 4 illus-trate modified ~orms of -test circuits which allow the 8 detector to be tes-ted from a remo-te location.
Dl~`SCI~rl'TI~N 1)l` TF~` Il.l,USTRATED EMBOD ~i~TS
Refer~ g to Figllre I of the drawin~ there is i.Llustrated a schema~ic diagrarn of an ioni~ation s~oke detector 10 which comprises a housing 12 ha~ing 11 an inner clectrode 16, an outer electrode 149 and a collector electrode 18.
12 The physical struc-ture of such detectors provides an i~ler or re~erence chamber 1~ 20 between the inner electrode 16 ~nd the collector electrode? and an outer or l/~ smolie detectillg chambel 22 betwcen t~e re~ercllce ellcl.rode arld ~ oul.cr electrode 14. r~c physical struc-tuIe o~ SUCil det,ectors i~ wcll knowrl in th( 1~ art, and are illustrated ill9 for example, U.S. patent 3J935l466 and United 17 Kingdom published application 2~013,39~A. An ioni~atio~ source 24 is provided 18 in the hou~ing to provide ion current flow when the detector i~ connected to a 19 power source p. The outer electrode 14 and the inner electrode 16 are connected across the power source 80 that ion culrent flow of a definite magnitude 21 flows between the inner and outcr electrodes when clean air is in the detector.
22 This ion current flow establishe6 a ~oltage on the collector electrode 23 of predetermined value, which voltage is applied to terminal Tl of a comparator 24 C, to be compared ~i-th a reference voltage established at ter~inal T~ ilom the junction 31 of a voltage divider consisting of resistors R1 and R2 connected 26 in serie~ across the powcr source P~
~Y-55 ?age 3 l ihZ592 1 When smoke enters the chamber, the smoke particles reduce the ion curren-t 2 flow, which reduces the voltage on the collector electrode. ~or example9 in
3 a particular detector, with a 9uppl~' voltage of ~ volts3 the voltage on the
4 collector electrode during clean air conditions, may be 5.5 volts. The reYistor~ R1 and R2 have values ~uch that the voltage on terminal T2 of the 6 comparator i~ 4.5 volt~. There~ore when the smoke den~ity in the chamber 7 becomcs ~reat enough to reduce the collector voltage to 4.5 volt~g the com-parator produces an output to the alarm actuating device A.
9 In the detector of this invention9 a test electrode 26 is provided in the housing between the collector and the outer electrode, in the smoke 11 detecting cha~ber. To apply a predete~mined voltage to the test electrode, 12 a voltage divider is provided9 which consists oi resistors R3 and R4 in 13 serie~ throu~h a junction J2 and in ~cries with a ~witch S~ acro~s the power 14 gource P, with the test electrode being connected to the junckion J2.
The test electrode i~ normally maintained at the ~ame potential as the 16 outer electrode, ~ince it i~ connected -to the outer electrode and the power 17 ~ource throu~h re~istor R3, and 6ince no au~3tantial c~rent flows through ~aid 18 resi~tor when the ~witeh S1 i8 open.
1~ ~owever when ~w;tch S1 i~ closed, current through ~3 and R4 establish a predetermined voltage on the te~t electrode tha-t is les~ than the voltage on 21 the ou-ter electrode 9 which causes a change in the electric iield distribution 22 in the chamber between the collector and the outer electrode. Thi~ ch~nge in 23 iield di~tribution causes a decrea3e in the volta~e on the collectorS and i~
24 the voltage applied to the te~t electrode i~ of the proper value, the collector voltage is reduced to a value just equal to that of the comparator reierence 26 voltage. Applying the proper ~oltage to the test electrode therefore will 27 ~imulate the amount oi ~moke in the housing at which the alarm i~ to be actuated.
_ 4 2~Z
1 Figure ~ is a grraph illustrating the relation between the voltage on 2 the test electrode and the percent smoke that each voltage simulates for a 3 particular detector.
4 If the detector is intended to provide an alarm signal when the concen-tration of smoke in the ch~mber reaches 1~ (which i9 establi~hed by the ratio of values of resistors R1 ~d R2, then it is secn rrom Figrure 2 that a test 7 voltage of about 5.8 vol-ts will be required to produce a test alarm nnder clean 8 air conditions. ~owever in the manufacture of such detectors in large quantities 9 manufacturing tolerances make it impractical to test the detectors to the exact alarm point. Therefore if a regulation issued by a government or 11 industry regrul~tory body requires that the detector respond to 6~ smoke for 12 C~~pl e, the detector can be m~muIacturcd -to a ~oal of responding to 1% smoke, 1~ with the test circuit being designed to simulate a smoke percentage intermediate 14 the required alarm point of 6% ~o~e and the designed alarm point o~ 1~ smoke.
Therefore the resistorq R3 and R3 will have values that will produce a test 16 ~oltage when switch S1 is closed that will ~imulate, ~or e~ample 3% smoke.
17 In the eml)odiment of Figure -l, switch S1 may be a magrnetically operated t~ switch so positione~ that the test may l)e con~ucte(l by applyin~ a magrnet to 1~ the exterior of the detector housing. The fact that the switch is in serie~
with the resistors ~3 ~d R4 prevents a surge of current when the swi-tch is 21 closed which migrht erroneously actua-te the alarm circuitry.
22 To enable the te3t to be conducted from a remote location, a ~odified 23 form of test circuit may be provided as illustrated in Figure 3. As shown 24 therein, the re~istors R3 and R4 are connected in series with the collector-emitter path of tran~istor T. ~he base of transistor T is connected to the 26 Junction J3 of resi~3tors R5 and R69 which resistors are connected to the power 27 ~30urce P through a switch S2, whi~h may be at a remote location such as at a 28 central control panel.
P~e 5 59~
1 Closing of ~witch S2 cause~ a predetermined voltage to be applied to the base 2 of transi~tor T, sufficient to cause conduction in $he emitter-collector pa-th 3 ~o -that the tegt voltage applied at junction J2. If the line from switch S2 4 ~to the de-tector i9 lon~ enough to voltsgc -tr~l~icnts, a ~oi~e suppression ca~acitor F may be pr~ idcd bctwe~n thc base f tran~i~-tor T and groimd.
6 Another embodiment of the invention that allows a remote test switch 7 iB shown in Figure 4, in which resi~tors R3 and R4 are connected in series 8 with a photo-re~ponsive device, such as photo-transistor PT, o~ an optically 9 coupled isclator. The light ~ource I, of the isolator may be co~nected -to the power ~ource P through a resistor R7 o-f suitable value, and switch S3. As in 11 the embodiment of FiguIe 3, the switch S~ may be located at a remote location.
1~ When thc switch S3 i8 closed, the resulting illumination of light L allows 13 conduction through the photo-responsive device to cau~e the test voltage to 14 appear at junction J2.
Although in the illustrated embodiments of the inven-tion, the te~t 16 electrode end circui-t are ~hown ~ being incorporated into a dual chQmber 17 detector, the invention can al~o be incorporated into a 0ingle ch~ber de-tector 18 or into the detector cha~ber of a two chamber detector.
19 Since certain other changes apparent to one skilled in the art may be made in the herein illustrated embodiments vf the device without depnrting 21 from the ~cope thereof, it i9 intended that all matter contained herein be 22 interpreted in an illustrative and not a limiting sense.
~-55 ge 6
9 In the detector of this invention9 a test electrode 26 is provided in the housing between the collector and the outer electrode, in the smoke 11 detecting cha~ber. To apply a predete~mined voltage to the test electrode, 12 a voltage divider is provided9 which consists oi resistors R3 and R4 in 13 serie~ throu~h a junction J2 and in ~cries with a ~witch S~ acro~s the power 14 gource P, with the test electrode being connected to the junckion J2.
The test electrode i~ normally maintained at the ~ame potential as the 16 outer electrode, ~ince it i~ connected -to the outer electrode and the power 17 ~ource throu~h re~istor R3, and 6ince no au~3tantial c~rent flows through ~aid 18 resi~tor when the ~witeh S1 i8 open.
1~ ~owever when ~w;tch S1 i~ closed, current through ~3 and R4 establish a predetermined voltage on the te~t electrode tha-t is les~ than the voltage on 21 the ou-ter electrode 9 which causes a change in the electric iield distribution 22 in the chamber between the collector and the outer electrode. Thi~ ch~nge in 23 iield di~tribution causes a decrea3e in the volta~e on the collectorS and i~
24 the voltage applied to the te~t electrode i~ of the proper value, the collector voltage is reduced to a value just equal to that of the comparator reierence 26 voltage. Applying the proper ~oltage to the test electrode therefore will 27 ~imulate the amount oi ~moke in the housing at which the alarm i~ to be actuated.
_ 4 2~Z
1 Figure ~ is a grraph illustrating the relation between the voltage on 2 the test electrode and the percent smoke that each voltage simulates for a 3 particular detector.
4 If the detector is intended to provide an alarm signal when the concen-tration of smoke in the ch~mber reaches 1~ (which i9 establi~hed by the ratio of values of resistors R1 ~d R2, then it is secn rrom Figrure 2 that a test 7 voltage of about 5.8 vol-ts will be required to produce a test alarm nnder clean 8 air conditions. ~owever in the manufacture of such detectors in large quantities 9 manufacturing tolerances make it impractical to test the detectors to the exact alarm point. Therefore if a regulation issued by a government or 11 industry regrul~tory body requires that the detector respond to 6~ smoke for 12 C~~pl e, the detector can be m~muIacturcd -to a ~oal of responding to 1% smoke, 1~ with the test circuit being designed to simulate a smoke percentage intermediate 14 the required alarm point of 6% ~o~e and the designed alarm point o~ 1~ smoke.
Therefore the resistorq R3 and R3 will have values that will produce a test 16 ~oltage when switch S1 is closed that will ~imulate, ~or e~ample 3% smoke.
17 In the eml)odiment of Figure -l, switch S1 may be a magrnetically operated t~ switch so positione~ that the test may l)e con~ucte(l by applyin~ a magrnet to 1~ the exterior of the detector housing. The fact that the switch is in serie~
with the resistors ~3 ~d R4 prevents a surge of current when the swi-tch is 21 closed which migrht erroneously actua-te the alarm circuitry.
22 To enable the te3t to be conducted from a remote location, a ~odified 23 form of test circuit may be provided as illustrated in Figure 3. As shown 24 therein, the re~istors R3 and R4 are connected in series with the collector-emitter path of tran~istor T. ~he base of transistor T is connected to the 26 Junction J3 of resi~3tors R5 and R69 which resistors are connected to the power 27 ~30urce P through a switch S2, whi~h may be at a remote location such as at a 28 central control panel.
P~e 5 59~
1 Closing of ~witch S2 cause~ a predetermined voltage to be applied to the base 2 of transi~tor T, sufficient to cause conduction in $he emitter-collector pa-th 3 ~o -that the tegt voltage applied at junction J2. If the line from switch S2 4 ~to the de-tector i9 lon~ enough to voltsgc -tr~l~icnts, a ~oi~e suppression ca~acitor F may be pr~ idcd bctwe~n thc base f tran~i~-tor T and groimd.
6 Another embodiment of the invention that allows a remote test switch 7 iB shown in Figure 4, in which resi~tors R3 and R4 are connected in series 8 with a photo-re~ponsive device, such as photo-transistor PT, o~ an optically 9 coupled isclator. The light ~ource I, of the isolator may be co~nected -to the power ~ource P through a resistor R7 o-f suitable value, and switch S3. As in 11 the embodiment of FiguIe 3, the switch S~ may be located at a remote location.
1~ When thc switch S3 i8 closed, the resulting illumination of light L allows 13 conduction through the photo-responsive device to cau~e the test voltage to 14 appear at junction J2.
Although in the illustrated embodiments of the inven-tion, the te~t 16 electrode end circui-t are ~hown ~ being incorporated into a dual chQmber 17 detector, the invention can al~o be incorporated into a 0ingle ch~ber de-tector 18 or into the detector cha~ber of a two chamber detector.
19 Since certain other changes apparent to one skilled in the art may be made in the herein illustrated embodiments vf the device without depnrting 21 from the ~cope thereof, it i9 intended that all matter contained herein be 22 interpreted in an illustrative and not a limiting sense.
~-55 ge 6
Claims (12)
1. An ionization smoke detector comprising first and second electrodes spaced to define therebetween a smoke detecting chamber, said second electrode being a collector electrode, an ion source positioned for emitting radia-tion into said smoke detecting chamber for causing ionization of a gas therein, a power supply connected to said first and second electrodes to establish ion current flow through said smoke detecting chamber, comparator circuitry connected to said collector electrode, said collector electrode being adapted to apply a predetermined voltage to said com-parator circuitry during clean air conditions, a first voltage divider network connected to said power supply and to said comparator circuitry, said first voltage divider network generating a reference voltage for application to said comparator circuitry, said reference voltage having a predetermined offset value from said clean air voltage applied to said comparator circuitry by said collector electrode, said comparator circuitry being adapted to generate an alarm signal when the voltage applied to said comparator circuitry by said collector electrode is equal to or less than said reference voltage, a test electrode disposed in said smoke detecting chamber between said first and second elec-trodes, a second voltage divider network connected to said power supply circuit and to said test electrode, and switch means connected to said second voltage divider network, said switch means having open and closed conditions and being connected to said second voltage divider network such that, when said switch means is in open condition, the voltage applied to said test electrode is the same as the voltage applied to said first electrode by said power supply, and when said switch means is in closed condition a test voltage is applied to said test electrode, said test voltage on said test electrode being effective to reduce the voltage on said collector electrode to a value equal to or less than the said reference voltage to cause said comparator circuitry to generate an alarm signal.
2. The ionization detector of claim 1 wherein the test voltage applied to said test electrode when said switch is closed is less than the voltage on said first electrode and greater than the clean air voltage of said collector electrode.
3. The ionization detector of claim 1 wherein said second voltage divider network includes two series-connected resistors, said switch means is connected in series with said two resistors, and said test voltage is generated at the junction of said two resistors.
4. The ionization detector of claim 3 wherein said switch comprises a transistor with the collector-emitter path being connected in series with said two resistors, and means for applying a voltage to the base of the transistor to cause current flow in said collect-or-emitter path to cause said test voltage to appear on said test electrode.
5. The ionization detector of claim 3 wherein said switch comprises an optically coupled isolator comprising a photo-responsive device connected in series with the second resistor between the test electrode and ground, and a light source positioned to illuminate the photo-responsive device when energized, and means for ener-gizing the photo-responsive device.
6. An ionization smoke detector comprising a housing, inner and outer electrodes spaced in said housing to define therebetween a smoke detect-ing chamber, a collector electrode in said smoke detect-ing chamber between said inner and outer electrodes, an ion source positioned in said housing for emitting radiation into said smoke detecting chamber for causing ionization of a gas therein, a power supply connected to said inner and outer electrodes to establish ion current flow through said smoke detecting chamber, comparator circuitry connected to said collec-tor electrode, said collector electrode being adapted to apply a predetermined voltage to said comparator circuitry during clean air conditions, a first voltage divider network connected to said power supply and to said comparator circuitry, said first voltage divider network generating a refer-ence voltage for application to said comparator circuitry, said reference voltage having a predeter-mined offset value from said clean air voltage applied to said comparator circuitry by said collector electrode, said comparator circuitry being adapted to generate an alarm signal when the voltage applied to said compara-tor circuitry by said collector electrode is equal to or less than said reference voltage, a test electrode disposed in said smoke detecting chamber between said outer and collector electrodes, said outer, test and collector electrodes being substantially parallel to one another, a second voltage divider network connected to said power supply circuit and to said test electrode, and switch means connected to said second voltage divider network, said switch means having open and closed conditions and being connected to said second voltage divider network such that, when said switch means is in open condition, the voltage applied to said test electrode is the same as the voltage applied to said outer electrode by said power supply, and when said switch means is in closed condition a test voltage is applied to said test electrode, said test voltage on said test electrode being effective to reduce the voltage on said collector electrode to a value equal to or less than the said reference voltage to cause said comparator circuitry to generate an alarm signal.
7. The ionization detector of claim 6 wherein said switch is a magnetically operated switch that is operated by applying a magnet to the exterior of the detector housing.
8. The ionization detector of claim 7 wherein the test voltage applied to said test electrode when said switch is closed is less than the voltage on said first electrode and greater than the clean air voltage of said collector electrode.
9. The ionization detector of claim 6 wherein said second voltage divider network includes two series connected resistors, said switch means is connected in series with said two resistors, and said test voltage is generated at the junction of said two resistors.
10. The ionization detector of claim 9 wherein said switch comprises a transistor with the collector-emitter path being connected in series with said two resistors, and means for applying a voltage to the base of the transistor to cause current flow in said collector-emitter path to cause said test voltage to appear on said test electrode.
11. The ionization detector of claim 9 wherein said switch comprises an optically coupled isolator comprising a photo-responsive device connected in series with the second resistor between the test electrode and ground, and a light source positioned to illuminate the photo-responsive device when ener-gized, and means for energizing the photo-responsive device.
12. The ionization detector of claim 9 wherein the test voltage applied to said test electrode when said switch is closed is less than the voltage on said first electrode and greater than the clean air voltage of said collector electrode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22438781A | 1981-01-12 | 1981-01-12 | |
| US224,387 | 1988-07-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1182592A true CA1182592A (en) | 1985-02-12 |
Family
ID=22840457
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000393916A Expired CA1182592A (en) | 1981-01-12 | 1982-01-11 | Ionization type smoke detector with test circuit |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS57164398A (en) |
| CA (1) | CA1182592A (en) |
| CH (1) | CH657222A5 (en) |
| DE (1) | DE3200620A1 (en) |
| ES (1) | ES8307060A1 (en) |
| GB (1) | GB2091485B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3904979A1 (en) * | 1989-02-18 | 1990-08-23 | Beyersdorf Hartwig | METHOD FOR OPERATING AN IONIZATION SMOKE DETECTOR AND IONIZATION SMOKE DETECTOR |
| US5189399A (en) * | 1989-02-18 | 1993-02-23 | Hartwig Beyersdorf | Method of operating an ionization smoke alarm and ionization smoke alarm |
| US9111427B2 (en) | 2009-07-07 | 2015-08-18 | Xtralis Technologies Ltd | Chamber condition |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4238788A (en) * | 1978-01-03 | 1980-12-09 | Teledyne Industries, Inc. | System for detecting a combustion process |
-
1982
- 1982-01-07 CH CH67/82A patent/CH657222A5/en not_active IP Right Cessation
- 1982-01-11 CA CA000393916A patent/CA1182592A/en not_active Expired
- 1982-01-11 ES ES508630A patent/ES8307060A1/en not_active Expired
- 1982-01-12 GB GB8200748A patent/GB2091485B/en not_active Expired
- 1982-01-12 DE DE19823200620 patent/DE3200620A1/en not_active Ceased
- 1982-01-12 JP JP57003242A patent/JPS57164398A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| CH657222A5 (en) | 1986-08-15 |
| ES508630A0 (en) | 1983-07-01 |
| GB2091485A (en) | 1982-07-28 |
| DE3200620A1 (en) | 1982-09-09 |
| ES8307060A1 (en) | 1983-07-01 |
| JPS57164398A (en) | 1982-10-08 |
| GB2091485B (en) | 1984-10-03 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4595914A (en) | Self-testing combustion products detector | |
| US3555532A (en) | Vapor or particle detection device | |
| US5243330A (en) | Fire detector system and method | |
| FI59498B (en) | IONISATIONSBRANDALARMANORDNING | |
| CA1134068A (en) | Smoke detector having unipolar ionization chamber | |
| US4097850A (en) | Means for adjusting and for testing a detecting device | |
| CA1182592A (en) | Ionization type smoke detector with test circuit | |
| US4021671A (en) | Ionization detector | |
| US5218347A (en) | Apparatus for detecting hazardous gases | |
| US4456907A (en) | Ionization type smoke detector with test circuit | |
| US4061922A (en) | Ultraviolet sensing device | |
| CA1056479A (en) | Smoke detector and alarm | |
| CN1028924C (en) | Ionization type smoke detector | |
| US3913082A (en) | Ionization aerosol detector | |
| US3514603A (en) | Ionization chamber detection apparatus having a low voltage source means | |
| US4112310A (en) | Smoke detector with photo-responsive means for increasing the sensitivity during darkness | |
| US4109240A (en) | Ionization-type fire sensing system | |
| US3781838A (en) | Products of combustion detector | |
| US4364031A (en) | Ionization smoke detector with increased operational reliability | |
| JPH0410119B2 (en) | ||
| CN2270251Y (en) | Ionic smoke concentration meter | |
| US3493950A (en) | Apparatus for detecting the presence of an ionizable fluid | |
| JPS62142922A (en) | Combustion sensing circuit | |
| JPS5821020Y2 (en) | Fire detector with test function | |
| CN211317390U (en) | Indoor environment detection system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |