US3723747A - Photoelectric detector with compensating photocell - Google Patents
Photoelectric detector with compensating photocell Download PDFInfo
- Publication number
- US3723747A US3723747A US00149637A US3723747DA US3723747A US 3723747 A US3723747 A US 3723747A US 00149637 A US00149637 A US 00149637A US 3723747D A US3723747D A US 3723747DA US 3723747 A US3723747 A US 3723747A
- Authority
- US
- United States
- Prior art keywords
- light
- means comprises
- spreading
- cell
- space
- 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 - Lifetime
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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
- G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
- G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/47—Scattering, i.e. diffuse reflection
- G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
- G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
-
- 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
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/06—Illumination; Optics
- G01N2201/063—Illuminating optical parts
- G01N2201/0638—Refractive parts
- G01N2201/0639—Sphere lens
Definitions
- ATTORNEY PHOTOELECTRIC DETECTOR WITH COMPENSATING PHOTOCELL Scatter type smoke detectors include an exciter lamp illuminating a space in which particulate matter such as smoke is to be detected, and a sensing photocell viewing the space which is nearly dark, but at very low illumination constantly sensed by the cell.
- a sensing photocell viewing the space which is nearly dark, but at very low illumination constantly sensed by the cell.
- the cells response to light scattered from a given amount of matter may vary with age, temperature, applied voltage and change of lamp illumination among other factors.
- the change of cell response required to trigger the threshold circuit is thereby varied, reducing the reliability of the detector or causing false alarms.
- the above factors can be temporarily compensated by connecting a substantially identical compensating cell in the threshold circuit and exposing it to light from the exciter lamp.
- a substantially identical compensating cell in the threshold circuit Such an arrangement is shown in U.S. Pat. No. 2,476,958 to C. N. Cahusac et al together with a shutter for varying the area of the compensating cells photosensitive surface exposed to light from the exciter lamp.
- a similar arrangement is shown in U.S. Pat. No. 3,409,885 to R. N. Hall which suggests that in addition to the adjustable shield or shutter, a filter over the cell can provide a further attenuation of light on the partly exposed photosensitive surface.
- the remaining small area of the com pensating cell surface must receive a substantially higher intensity of light than that falling on the sensing cells in order to match the impedance of the totally illuminated sensing cell.
- a third example of a factor causing differences in the responses of two cells is the pre-existing level of light intensity on respective cells.
- the percentage of change in cell conductance with a given change of incident light intensity will vary greatly depending on the initial light level at the photoconductive surface of the cell.
- a change in emission from the exciter lamp may result in a cell imbalance which reduces the detectors sensitivity to smoke, or on the other hand causes a false alarm.
- apparatus for detecting matter in a space comprises a light source for illuminating the space, first and second photosensitive devices having substantially equal light sensitive areas, the first of said devices being exposed to light scattered from matter in the space and the second device being exposed to light from the source, and means to control the amount of light on the second device, wherein said control means includes means to spread the controlled amount of light over substantially the same light sensitive area of the second device as the first device exposed to light in said space.
- FIG. 1 is a sectional view of a dual cell smoke detector having a light controller
- FIG. 2 is a section on line 2-2 of FIG. 1;
- FIG. 3 is a sectional view like FIG. 1 of a smoke detector having a modified form of light controller
- FIG. 4 is an elevation showing the light controller of FIG. 3 enlarged.
- FIG. 5 is a sectional view like FIG. 1 showing a further modification.
- FIGS. 1 and 2 show a scatter type of smoke detector which comprises a semi-circular space enclosed by an opaque triangular block 3, and by a semi-circular wall 4 and upper and lower walls 6 and 7 of porous material which substantially exclude ambient light from the space, but rather freely admit air-borne particles into the space as fully described in U.S. Pat. No. 3,497,303.
- an exciter lamp 8 mounted outside the triangular block 3 is an exciter lamp 8 whose rays are directed by a ball lens 9 along a path 11 through a passage 12 into the enclosed space.
- a first photoconductive cell 1 recessed in the block 3 and having a disk-shaped photosensitive area 1a views the space through a bullet lens 13 along a path 14 through a passage 16 in the block 3.
- substantially the whole photosensitive area la of the first photocell 1 receives a very low but finite level of light leaked through the porous walls 4, 6 and 7, or from exciter lamp illumination reflected from the interior surfaces of the walls through the passage 16. This residual light level affects the ageing and sensitivity of the cell to light changes.
- a second photoconductive cell 2 selected for substantially identical response characteristics and photosensitive area 2a as for the first cell 1, is shielded from light in the illuminated space but receives some of the light from the exciter lamp 8.
- the second photocell 2 is recessed in the block 3 and optically communicates with the ball lens 9 through tapering passages 18 and 19 and a straight passage 21 terminating at the ball lens.
- the passage 18 adjacent the photocell 3 flares wider than the photosensitive area 2a.
- Light transmission from the lens into the passage 21 is weak, and is further reduced by a screw plug 22 threaded into the block 3 and adjustable in and out of the passage 21, more or less to obstruct light transmitted through the passage onto the photosensitive surface 2a of the second photocell.
- the light is reduced to a level such that it reaches the second photocell 2 in an energy amount (lumens) equivalent to the amount on the first photocell 1 in normal, no smoke, condition.
- a frosted glass diffusing disk 23 located beyond the screw plug 22 and between the tapering passages 18 and 19.
- the diffuser disk 23 spreads light fairly anisotropically throughout the tapered passage 18 and substantially uniformly over the photosensitive area, and insures that in addition to receiving the same amount of light (lumens) the two photosensitive areas 1a and 2a receive light at the same level of intensity (foot candles) and color temperature over the same areas.
- the above additionally provided conditions will allow the two cells to age at the same rate with respect to area, light intensity and temperature.
- FIGS. 3 and 4 show an alternate way of controlling the amount and spreading of light on the photosensitive area 2a.
- Light from the ball lens 9 in a triangular block 3a is transmitted to the photosensitive area 2a through a straight passage 26 and a tapered passage 27 flaring wider than the photosensitive area 2a.
- a modified screw plug 22a carries a circular vane 28 disposed in the straight passage 26. Angular adjustment of the plug and vane adjust the amount of light transmitted to the photocell 2.
- the circular vane 28 has a high reflectance, diffuse reflecting surface such as provided by flat white optical paint.
- the walls of the passages26 and 27 are also coated with diffuse reflecting paint. With such a diffuse surface on the vane and passage walls, or either of them, a controlled amount of light is spread very uniformly over the photosensitive surface 2a as in the case of FIGS. 1 and 2.
- the triangular block 3b has a flared passage 29 and straight passage 28 between the ball lens 9 and photocell 2.
- a plug 22 like that shown in FIGS. 1 and 2 controls light transmitted through the passages.
- a translucent cylinder of an internally diffusing solid such as milky glass and like plastic materials such as Nylon and Teflon.
- Apparatus for detecting particulate matter in a confined space comprising: a light source for illuminating the space, first and second solid state photosensitive devices having substantially equal light sensitive areas, the first of said devices being exposed over its total area to light scattered from matter in the space and the second device being exposed to light from the source, said devices being connected to an alarm circuit so that the second device compensates for variations in sensitivity of the first device, and means to control the amount of light on the second device, wherein said control means includes means to spread the controlled amount of light over substantially the same light sensitive area of the second device as the area of the first device exposed to light in said space, thereby to light age the two photosensitive devices substantially equally.
- control means comprises means for adjusting light from said source, and said spreading means is between the adjusting means and the second light sensitive area.
- control means comprises means for diffusing controlled light over substantially the entire light sensitive area of said second device.
- said spreading means comprises diffuse light transmitting means.
- said spreading means comprises an internally light diffusing solid.
- Apparatus according to claim 1 characterized by wall means forming a light passage between the light source and second device, adjustable means variably obstructing said passage, and diffusing means in said passage between the adjustable means and device.
- Apparatus according to claim 9 wherein said spreading means comprises a diffuse reflecting surface on said wall means.
- control means is adjustable through the range of light intensities normally falling on the first photosensitive device.
Landscapes
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Business, Economics & Management (AREA)
- Emergency Management (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
- Fire-Detection Mechanisms (AREA)
- Optical Measuring Cells (AREA)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US14963771A | 1971-06-03 | 1971-06-03 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3723747A true US3723747A (en) | 1973-03-27 |
Family
ID=22531192
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US00149637A Expired - Lifetime US3723747A (en) | 1971-06-03 | 1971-06-03 | Photoelectric detector with compensating photocell |
Country Status (6)
Country | Link |
---|---|
US (1) | US3723747A (de) |
CA (1) | CA963122A (de) |
DE (1) | DE2165697A1 (de) |
FR (1) | FR2141655B1 (de) |
GB (1) | GB1370811A (de) |
IT (1) | IT942068B (de) |
Cited By (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS49148088U (de) * | 1973-04-20 | 1974-12-20 | ||
US3863076A (en) * | 1973-07-24 | 1975-01-28 | Electro Signal Lab | Optical smoke detector |
JPS5092181A (de) * | 1973-12-13 | 1975-07-23 | ||
US3931525A (en) * | 1972-09-21 | 1976-01-06 | Ferranti, Limited | Detection of blemishes in surfaces |
US3936814A (en) * | 1974-04-29 | 1976-02-03 | Bernz-O-Matic Corporation | Smoke detector and alarm |
US3992102A (en) * | 1974-04-17 | 1976-11-16 | Hochiki Corporation | Photoelectric smoke detector with means for adjusting the amount of light projected into the detection region |
US4114177A (en) * | 1975-05-01 | 1978-09-12 | Bell Telephone Laboratories, Incorporated | Optically coupled device with diffusely reflecting enclosure |
EP0099729A1 (de) * | 1982-07-14 | 1984-02-01 | Chloride Group Public Limited Company | Detektor für suspendierte Teilchen |
US20030209670A1 (en) * | 2002-05-13 | 2003-11-13 | Precision Instrument Development Center, National Science Council | Sensitivity adjusting equipment of photoelectric smoke detector |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DK237780A (da) * | 1979-06-19 | 1980-12-20 | Secon Co Ltd | Roegdetektor |
CN102768185A (zh) * | 2006-08-02 | 2012-11-07 | 阿瓦尼斯实验室科技公司 | 光度计和操作方法 |
Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1968816A (en) * | 1930-07-18 | 1934-08-07 | Sewell M Corbett | Meter for quantitatively determining the amount of foreign matter in air |
US2510347A (en) * | 1945-10-19 | 1950-06-06 | Rca Corp | Photoelectric comparator having two bridge circuits |
US2519081A (en) * | 1949-01-07 | 1950-08-15 | Standard Oil Dev Co | Process and apparatus for determining rate of composition change |
US2791932A (en) * | 1953-07-30 | 1957-05-14 | Specialties Dev Corp | Light responsive apparatus for detecting suspended matter in a fluid |
US2967946A (en) * | 1957-10-31 | 1961-01-10 | Standard Oil Co | Light transmissivity control instrument |
US3365661A (en) * | 1965-04-26 | 1968-01-23 | Anaconda Wire & Cable Co | Method and apparatus for locating leaks in a cable by determining the distance to a short circuit in the cable |
US3439178A (en) * | 1965-02-08 | 1969-04-15 | Owens Illinois Inc | Radiation-sensitive apparatus for inspecting wall thickness of hollow containers |
US3505529A (en) * | 1968-02-08 | 1970-04-07 | Bliss Co | Radiation sensitive smoke detecting device |
US3518437A (en) * | 1968-03-20 | 1970-06-30 | Shell Oil Co | Apparatus for measuring haze in flowing liquids utilizing an operational amplifier with photosensitive feedback and input resistors for computing the ratio of scattered to directly transmitted light |
US3553470A (en) * | 1967-03-16 | 1971-01-05 | Richards & Co Ltd George | Apparatus for generating an approximation to a sine wave including a reading head with two spaced areas for scanning an optical grating |
-
1971
- 1971-06-03 US US00149637A patent/US3723747A/en not_active Expired - Lifetime
- 1971-12-10 GB GB5744871A patent/GB1370811A/en not_active Expired
- 1971-12-18 IT IT9803/71A patent/IT942068B/it active
- 1971-12-22 CA CA130,830A patent/CA963122A/en not_active Expired
- 1971-12-28 FR FR717147163A patent/FR2141655B1/fr not_active Expired
- 1971-12-30 DE DE19712165697 patent/DE2165697A1/de active Pending
Patent Citations (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1968816A (en) * | 1930-07-18 | 1934-08-07 | Sewell M Corbett | Meter for quantitatively determining the amount of foreign matter in air |
US2510347A (en) * | 1945-10-19 | 1950-06-06 | Rca Corp | Photoelectric comparator having two bridge circuits |
US2519081A (en) * | 1949-01-07 | 1950-08-15 | Standard Oil Dev Co | Process and apparatus for determining rate of composition change |
US2791932A (en) * | 1953-07-30 | 1957-05-14 | Specialties Dev Corp | Light responsive apparatus for detecting suspended matter in a fluid |
US2967946A (en) * | 1957-10-31 | 1961-01-10 | Standard Oil Co | Light transmissivity control instrument |
US3439178A (en) * | 1965-02-08 | 1969-04-15 | Owens Illinois Inc | Radiation-sensitive apparatus for inspecting wall thickness of hollow containers |
US3365661A (en) * | 1965-04-26 | 1968-01-23 | Anaconda Wire & Cable Co | Method and apparatus for locating leaks in a cable by determining the distance to a short circuit in the cable |
US3553470A (en) * | 1967-03-16 | 1971-01-05 | Richards & Co Ltd George | Apparatus for generating an approximation to a sine wave including a reading head with two spaced areas for scanning an optical grating |
US3505529A (en) * | 1968-02-08 | 1970-04-07 | Bliss Co | Radiation sensitive smoke detecting device |
US3518437A (en) * | 1968-03-20 | 1970-06-30 | Shell Oil Co | Apparatus for measuring haze in flowing liquids utilizing an operational amplifier with photosensitive feedback and input resistors for computing the ratio of scattered to directly transmitted light |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3931525A (en) * | 1972-09-21 | 1976-01-06 | Ferranti, Limited | Detection of blemishes in surfaces |
JPS49148088U (de) * | 1973-04-20 | 1974-12-20 | ||
US3863076A (en) * | 1973-07-24 | 1975-01-28 | Electro Signal Lab | Optical smoke detector |
JPS5092181A (de) * | 1973-12-13 | 1975-07-23 | ||
US3992102A (en) * | 1974-04-17 | 1976-11-16 | Hochiki Corporation | Photoelectric smoke detector with means for adjusting the amount of light projected into the detection region |
US3936814A (en) * | 1974-04-29 | 1976-02-03 | Bernz-O-Matic Corporation | Smoke detector and alarm |
US4114177A (en) * | 1975-05-01 | 1978-09-12 | Bell Telephone Laboratories, Incorporated | Optically coupled device with diffusely reflecting enclosure |
EP0099729A1 (de) * | 1982-07-14 | 1984-02-01 | Chloride Group Public Limited Company | Detektor für suspendierte Teilchen |
WO1984000429A1 (en) * | 1982-07-14 | 1984-02-02 | Chloride Group Plc | Suspended particle detector |
US20030209670A1 (en) * | 2002-05-13 | 2003-11-13 | Precision Instrument Development Center, National Science Council | Sensitivity adjusting equipment of photoelectric smoke detector |
US6797959B2 (en) * | 2002-05-13 | 2004-09-28 | Precision Instrument Development Center, National Science Council | Sensitivity adjusting equipment of photoelectric smoke detector |
Also Published As
Publication number | Publication date |
---|---|
FR2141655A1 (de) | 1973-01-26 |
DE2165697A1 (de) | 1972-12-14 |
GB1370811A (en) | 1974-10-16 |
FR2141655B1 (de) | 1973-07-13 |
IT942068B (it) | 1973-03-20 |
CA963122A (en) | 1975-02-18 |
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