Abstract: A directionally-sensitive flame detection apparatus and method for determining the presence of flame in a combustion chamber zone of a gas turbine. A radiation detector is coupled to the monitored combustion zone by a radiation collimator having mechanically-lowered internal reflectance so as to enhance the effective collimation angle. In this manner, a narrowed detector view angle is provided that is substantially independent of radiation wavelength or the material properties of the collimator tube.

Abstract: In one embodiment a bundle of optic fibers of different lengths are inserted through the case wall of a solid fuel or a hybrid rocket motor and extends through the wall of the fuel grain to the edge of the bore in center thereof. As the grain burns in a normal manner, from the center toward the outer periphery of the case, the bright flame of ignition is seen at the end of the fiber optic fiber adjacent to the flame. The length of each fiber in the bundle is used to determine the burn rate and amount of grain left to ignite. In another embodiment different length fibers of a bundle are looped into the grain and back to the exterior of the case and light emitting diodes are positioned at one end of each fiber with a light-detecting means at the other end. The light through the diodes is monitored to detect a no-light condition which exists when a fiber is destroyed by the burn. In yet another embodiment a single optic fiber is used with a light source and a light reception means at one end.

Abstract: A method of detecting flame within a region where flame is expected. Radiation emissions from the region are measured within selected portions of the visible and infra-red frequency bands. Spectral characteristics of the two measurements, including their auto spectra, coherency and transfer function, are derived. The derived spectral characteristics are compared with prestored spectral signatures representative of the spectral characteristics of radiation emitted from the region within the selected portions of the visible and infra-red frequency bands while known flame conditions prevail within the region--thereby estimating the deviation of the derived spectral characteristics from the prestored spectral signatures. The deviations aforesaid are compared with predetermined threshold alarm values to assess the presence or absence of flame.

Abstract: The presence of a flame from a burner is determined by analyzing the signal produced by a radiation sensor aimed at a burner. Specifically, a Fourier transformation is applied to the signal producing amplitude values for a spectrum of component frequencies produced by changes in the power of the flame over time. A logarithmic value is derived for each of the amplitude values. The degree of linearity of the distribution of the component frequency logarithmic amplitude values provides an indication of the flame presence. Several parameters, including integrated linear error, linearity regression correlation and slope difference, provide an indication of the degree of linearity. A plurality of values for each of these parameters are produced during an interval of time.

Abstract: A circuit for detecting presence of a flame receives a flame signal from a standard photocell positioned to receive radiation from the flame and digitally processes the amplitude variations in the photocell's output to sense for the presence of frequencies near a frequency which is characteristic of a flame. The frequencies substantially higher than the characteristic frequency are filtered from the signal, and the remaining signal is sampled at a frequency which is preferably four times the characteristic frequency. The samples are converted to digital values and processed using a discrete Fourier transform. If the value resulting from the transform operation exceeds a preselected value, presence of a flame is essentially certain. Such digital processing allows use of a dedicated microcircuit or a microprocessor for the flame sensing function and avoids the need for many large discrete components.

Abstract: A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to a radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. The detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor of cable 12 includes an optical filter 32 having a temperature dependent radiation transmission characteristic. Radiation from a fire passes via cable 12 to the detector 18.

Abstract: A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. Detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns, a mid-wavelength band of approximately 1.3 to 1.5 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor is doped with a material selected for its temperature dependent fluorescent emission characteristics. Radiation from a fire passes via cable 12 to the detector 18. A pulse of radiation from source 28 passes from a coupler 26 and 26a to the cable 12.

Abstract: A flame detector that comprises a housing adapted to contain a flame sensor and circuitry for processing signals produced by the sensor; the housing has a predetermined outer diameter, and a thin, highly thermally reflective coating is adhered to an outer surface of the housing to shield the sensor and circuitry from high ambient temperatures, whereby the detector is operable at the high ambient temperatures while having an outer diameter that is substantially the same as the predetermined diameter.

Abstract: A method of detecting flame within a region where flame is expected. Radiation emissions from the region are measured within selected portions of the visible and infra-red frequency bands. Spectral characteristics of the two measurements, including their auto spectra, coherency and transfer function, are derived. The derived spectral characteristics are compared with prestored spectral signatures representative of the spectral characteristics of radiation emitted from the region within the selected portions of the visible and infra-red frequency bands while known flame conditions prevail within the region--thereby estimating the deviation of the derived spectral characteristics from the prestored spectral signatures. The deviations aforesaid are compared with predetermined threshold alarm values to assess the presence or absence of flame.

Abstract: A light collection device for use in a flame emission detection system such as an on-line, real-time alkali concentration process stream monitor is disclosed which comprises a sphere coated on its interior with a highly diffuse reflective paint which is positioned over a flame emission source, and one or more fiber optic cables which transfer the light generated at the interior of the sphere to a detecting device. The diffuse scattering of the light emitted by the flame uniformly distributes the light in the sphere, and the collection efficiency of the device is greater than that obtainable in the prior art. The device of the present invention thus provides enhanced sensitivity and reduces the noise associated with flame emission detectors, and can achieve substantial improvements in alkali detection levels.

Abstract: An alarm system for warning of a creosote chimney fire hazard, having both means to produce a visible alarm when the creosote temperature is nearing the creosote flash point, and means to produce an audible alarm when light from actual ignition of a creosote fire is detected. The invention also provides means to discriminate against detection of wood fire light, to minimize false alarms.

Abstract: An image processing method for flame monitoring is based on the formation of a video signal characteristic to the combustion process. In accordance with the method, the flame is monitored by each fire-box camera essentially from its side, whereby the video signal is adapted to cover at least an entire ignition area of a single burner, the video signal is continually processed to define the average intensity level corresponding to the steepest intensity gradients, and for each averaged level, the corresponding spatial or time coordinates of the continuous video signal, which define the location of the ignition area, are determined. The method extracts from the ignition and combustion process abundant information helpful in the control of combustion.

Abstract: A flame detector, for use with a photocell which produces a flame signal when the photocell is exposed to a flame, is used for detecting the presence of a flame. An input circuit is coupled to the photocell for receiving and buffering the flame signal. The buffered flame signal is filtered and amplified in a filter. An output circuit further amplifies the filtered flame signal providing an output flame signal. A switch is also used in the flame detector for substantially short circuiting the flame signal to a known value upon receiving a switch-close signal from either a test computer or from a hot refractory detection circuit. A flame-out condition is detected by the hot refractory detection circuit which generates an HRD signal causing the flame signal to be substantially short circuited to a known value thereby eliminating a false flame signal caused by hot refractory shimmering.

Abstract: A fiber optics based optical emission line monitoring system is provided in which selected spectral emission lines, such as the sodium emission line, may be detected in the presence of interfering background radiation. A combustion flame is fed by a diverted portion of a process stream and the common end of a bifurcated or quadfurcated fiber optic light guide is adapted to collect light from the flame. The light is guided through the branches of the fiber optic cable to bandpass filters, one of which is adapted to each of the branches of the fiber optic light guide. The bandpass filters are centered at wavelengths corresponding to the emission lines to be detected and two separate filters are required for each species being detected. The first filter has a bandwidth of about 3 nms and the second filter has a bandwidth of about 10 nms. Light detectors are located to view the light passing through the bandpass filters and amplifiers are connected to receive signals from the light detectors.

Abstract: A method of detecting fires utilizing its flicker frequency spectrum provides a standard theoretical flicker frequency spectrum which is compared to the real time spectrum over a 2 second time period. The comparison includes whether or not the real time fire spectrum deviates from the idealized fire spectrum by a minimum amount and has further discrimination against false fire signals, including the extent of time of the real time spectrum is outside a predetermined window and a limit on maximum deviations.

Abstract: A fire detection system has a detector for sensing optical radiation from a spark or flame or hot spot and an optical waveguide comprising an elongate hollow tube, having an inlet end portion for placement in a hostile, hazardous environment, and having an outlet end portion for emitting light rays to the detector and for placement in a benign, non-hazardous environment, and having a reflective inner surface forming a passage for transmitting the optical radiation from the tube inlet end portion to the tube outlet end portion by successive internal reflections.The elongate hollow waveguide tube is sealed at the inlet end portion by a lens which admits the optical radiation to the tube; and at the outlet end typically by the detector. The sealed tube is filled with an inert gas, such as nitrogen, which helps to maintain the reflective interior surface of the tube.

Abstract: An apparatus for monitoring a flame which emits light, the apparatus comprising: (a) a detector for detecting the light and outputting a signal corresponding to the light; (b) a casing for enclosing the detector, the casing including an aperture for the light going to the detector; (c) a blower for supplying air to the casing; and (d) a windmill for periodically shuttering the light to the detector with a shuttering frequency, the windmill being driven by the supplied air.

Abstract: A propellant sample combustion apparatus employing a multiply optical ported pressure vessel for sample illumination, sample viewing, and sample burn face elevation is described. High-speed motion picture filming using short-duration high-intensity laser provided optical illumination from a copper-vapor laser is employed. Details of the employed pressure vessel, a burn inhibiting coating for the propellant sample, a laser coherence spoiler, and a sample level maintaining closed-loop apparatus are also disclosed.

Abstract: This invention relates to an automatic fire extinguishing equipment adapted to direct a nozzle towards the position of a flame starting within a supervising zone so as to discharge a fire extinguishing liquid to extinguish the flame, which equipment comprises a flame detecting apparatus including a detecting element for detecting a flame and device for scanning and driving the detecting element in a horizontal direction and a vertical direction, for searching the supervising zone and outputting data concerning the flames; a storage section for storing the detection data from the flame detecting apparatus; a fire extinguishment controlling section which decides the sizes of the distributed flames on the basis of the storage data from said storage section; a nozzle assembly including the nozzle and device for controlling the direction of the nozzle in response to a control from the fire extinguishment controlling section.

Abstract: A system for detecting a flame or droplets of burning polypropylene in an area below an upper surface of a conventional wet bench used in semiconductor production includes at least one sensor, a threshold detector, a discrimination, a counter and a latch. The sensor detects radiation generated by activity in the area and for generating a sensor signal in response to the detected radiation. The threshold detector determines whether the activity has a cross-sectional area which exceeds a predetermined threshold area. The discriminator determines whether the activity displays a flicker rate or a droplet rate that is within the predetermined flicker rate range.

Abstract: A flame detecting apparatus and a flame detecting method which utilizes a flame detector having a directivity and provided with a photodetector such as a photodiode or a phototransistor which produces a photo-output in response to the intensity of light incident thereupon. The flame detector is scanned sequentially in the horizontal and the vertical direction within a supervisory region. When a photo-output from said flame detector obtained in the horizontal or vertical scanning by said scanning means exceeds a predetermined threshold value, one of the horizontal and the vertical scanning is suspended, while repeating the other, vertical or horizontal, scanning at the same horizontal or vertical position several times. Flame determination is made when the changes in the photo-outputs, which is obtained through the repeated scanning, exceed a predetermined value and they last over a predetermined scanning angle.

Abstract: A self-powered control system for a gas-fired appliance having a pilot burner and a main burner includes an emissive surface in the flame of the pilot burner and a photovoltaic device for irradiation from the emissive surface for providing electrical power for the control system. Two normally closed electromagnetic latching valves are arranged in series between a source of fuel gas and the main burner with a connection to the pilot burner between the two valves. The first valve is latched open when the photovoltaic device is irradiated by the emissive surface and is unlatched to close when the device is not so irradiated. The second valve is unlatched to close when the main burner is not burning. A double acting solenoid or the like is used for sequentially opening the first and second valves for lighting the pilot and main burners. A safe, reliable control system is thereby provided without external electrical power. Similar principles are used for powering a safety flue damper and air flow fan.

Abstract: A system and method for detecting a fire source in a supervised region by means of fire detectors which effectively scan all over such region. A plurality of reference fire sources of the same geometric shape of the minimum size to be regareded as a fire are assumed to be located in successive predetermined position on the floor of the supervised region. Vertical control means successively sets the vertical deflection angles of each detector along the respective straight lines from each detector which graze by the upper end of the respective fire sources and to the lower end of the succeeding fire source. The system also comprises horizontal control means for causing the detectors to horizontally scan the supervised region. Upon detection of a fire, the detectors provide fire detection signals to a central processor unit which then actuates a spray nozzle to direct fire extinguishing fluid on the fire.

Abstract: A flame detector in which an infrared ray sensor having a specific infrared ray sensitivity and a visible ray sensor having a specific visible ray sensitivity are provided and output signals from both sensors are amplified by amplifiers, which in turn provide output signals to a phase discriminator circuit, the output signal from the amplifier for the infrared sensor output being also fed to a rectifier circuit for rectifying only a predetermined level or higher portion of the amplified output; an output signal from the rectifier circuit is fed to an integrator circuit and also fed to another integrator circuit through a switch which is opened when the output level of the phase discriminator circuit is "H"; then output signals from the integrator circuits are compared by a comparator and at the same time the output signal from said another integrator circuit is compared with a preset value by a comparator; and output signals from both comparators are fed to a control circuit which issues an alarm when the out

Abstract: A precise position control for maintaining the burn face of a propellant sample within a precise optical depth of field positional range during burn face recession that may be non-uniform in nature. The position control employs an array of laser excited binary signal optical sensors with closed loop digital and analog electronic signal processing.

Abstract: In a flame detector having an optical head, a plurality of light-taking optical fibers are arranged so as to provide different directions of fields of vision at their front ends. Therefore, the watching regions of burner flame has been widened, and even if the primary combustion zone moves back and forth with respect to the tip of the burner due to the change in load, the flame can be accurately detected providing high reliability. Junction optical fibers and wiring optical fibers are separately provided in addition to the light-taking optical fibers. Therefore, when one or more optical fibers are damaged, only the damaged optical fibers are required to be replaced with new ones providing cost reduction in maintenance. Two or more photosensitive elements having different sensitive wavelength regions are used. Therefore, various types of flames having various wavelengths can be effectively detected providing wider detection range when compared with conventional apparatus.

Abstract: A fire sensing system utilizing fiber optics to extend the physical range of radiation sensing elements into areas and environments which are physically inaccessible to, and/or destructive of, such sensors and their associated electronic circuitry. The fiber optics are combined with signal processing circuitry to achieve reliable fire sensing systems which present particular advantages in special applications.

Abstract: A warning light device for blown fuse caps having a photosensitive circuit mounted inside an adapter casing that mounts over and is exposed to the fuse element of the fuse caps. The device is powered by batteries contained inside the casing and includes battery energy saving circuits in the form of an intermittent circuit or a low duty cycle circuit that is suitable to provide a visual indication periodically to the user. Light emitting diodes are used as a low power consumption indicating light.

Abstract: A furnace system connected to a burner including a furnace for burning a fuel and air ejected from the burner into the furnace to produce a flame therein, and a combustion condition determining device for determining the conditions of combustion of the fuel in a zone of the flame extending along different strata thereof by collecting light in the flame at one point in the flame by moving such point. Signals outputted by the combustion condition determining device are utilized for monitoring or controlling the flame and controlling exhaust emission control devices for controlling exhaust emissions produced by the combustion of the fuel. Control of the conditions of combustion of the flame can be effected quickly with a high degree of precision by monitoring the flame.

Abstract: An apparatus for detecting an increase in heat is provided which utilizes a light path such as a fiber optic cable which is coupled between a light source and a light detector. The fiber optic cable has predetermined light transmission characteristics which are changeable in response to an increase in heat in the vicinity of the cable. As a result, the amount or frequency of light detected by the light detector will change in response to the increase in heat. The apparatus is also described in connection with an electrostatic paint spray system.

Abstract: A flame analyzer for analyzing one or more qualities of a flame from a burner, comprises a fiber optic array including a plurality of optic fibers each having a light-receiving end lying in a line and facing the flame. The line extends parallel to the flame and burner axis or may extend perpendicular to that axis. The light received by the fiber optic array is provided as a sheet of light to a monochromator which spreads the light into its component wave lengths. A pair of spaced apart arrays of light detectors is then utilized to measure the light at two discrete wave lengths. The detection produces signals that can be analyzed to generate temperature and particles distribution values for the flame across its length or width.

Abstract: A method of imaging the surface of an object at high temperature includes the steps of: irradiating the surface of a high-temperature object with two different kinds of pulses of monochromatic light of a fundamental wave and a harmonic thereof; passing the reflected light from the surface of the object through both an interference filter which allows only the two different kinds of monochromatic light to pass and a high-speed optical switch thereby to remove any background light component; drawing out only the reflected light of the pulses and leading the same to an image generating mechanism where it is converted into an image; and controlling the voltage applied to the high-speed optical switch thereby to adjust the mixing ratio between two wavelengths.

Abstract: A fire sensor device of the type capable of detecting flame and smoke. The fire sensor device has a detector unit having a condenser lens for determining variations in the brightness of a space on the basis of variations in the illumination thereof which occur due to the movement of flames of a fire or the presence of smoke therein. The fire sensor device has two frequency-detection circuits which have different set points and to which the detector unit is connected. The frequency and amplitude of a signal output from the detector unit and the number of pulses generated by the detector unit are computed, and the presence of a fire is detected on the basis of the duration of the signal.

Abstract: A flame monitor senses flame brightness and produces two signals corresponding to rapid brightness variations and average brightness. By comparing rapid signal variations to a fraction of the average a threshold ON-OFF signal representing normal flame operation is obtained that can be processed as a fail-safe indication and control. High and low limit thresholds can be set and compared with average brightness as a further condition of proper flame operation.

Abstract: A fire detection system incorporating fiber optics and having a selectively energizable light source for applying light pulses to a fiber optics path and a one way light transmitting element, such as a dichroic mirror, at the remote end of the fiber optics path for reflecting the pulses back to the detection portion of the system, thus providing a Built In Test Equipment (BITE) test capability in the system. Instead of a dichroic mirror, a bandpass filter may be used as the light transmitting member. The bandpass filter is selected to transmit light with wavelengths in the range from about 1.3 to 1.5 microns, in which case the light source is a light emitting diode (LED) emitting light at a wavelength of approximately 0.9 microns. The fiber optics path includes a branch which is coupled to the light source. This branch may comprise one fiber of a multi-fiber bundle or it may be an auxiliary fiber of a commercially available fiber optics combiner.

Abstract: A fiber optics based optical emission line monitoring system is provided in which selected spectral emission lines, such as the sodium D-line emission in coal combustion, may be detected in the presence of interferring background or blackbody radiation with emissions much greater in intensity than that of the emission line being detected. A bifurcated fiber optic light guide is adapted at the end of one branch to view the combustion light which is guided to a first bandpass filter, adapted to the common trunk end of the fiber. A portion of the light is reflected back through the common trunk portion of the fiber to a second bandpass filter adapted to the end of the other branch of the fiber. The first filter bandpass is centered at a wavelength corresponding to the emission line to be detected with a bandwidth of about three nanometers (nm). The second filter is centered at the same wavelength but having a width of about 10 nm.

Abstract: An analog-type fire detector for detecting, in the form of an analog amount, a change in physical phenomena caused by occurrence of a fire, which intermittently detects a change in the ambient physical phenomena caused by occurrence of a fire, generates an analog signal corresponding to an amount of the change, converts the analog signal into a pulse signal of a duration corresponding to the level of the signal, generates periodically from a reference pulse generating means a reference pulse of a predetermined duration, detects by a discriminating means a difference in pulse durations between the output signal from the pulse duration converting means and the reference pulse, charges or discharges a capacitor corresponding to the difference detected, and hold-outputs for a predetermined period by a hold-outputs means a signal corresponding to a voltage across the capacitor at the time when the charging or discharging is stopped.

Abstract: A fail-safe, self-checking flame monitoring circuit is provided without the use of a mechanical shutter in which a photodetector provides a signal corresponding to flame intensity (including flicker), an amplifier amplifies the signal, the amplification is controlled by a negative feedback circuit in relation to the peak amplitude of the signal (including flicker) such that all frequencies down to DC are amplified equally, and all amplified signals are passed, without threshold, downstream for further processing.

Abstract: A method of diagnosing a combustion state in a furnace of a boiler wherein the shape of the root part of a flame (namely, the part closer to the fuel jet port of a burner) is picked up by an image sensor or the like, and the combustion state is diagnosed from the shape. Concretely, the relationships between the shapes of the root parts of flames and the combustion states of the furnace, e.g., the amount of CO or the amount of NOx are experimentally or empirically ensured and are stored in advance, one of the patterns of the stored flame shapes is selected on the basis of the shape of the root part of the flame actually observed, and the combustion state of the furnace is judged the combustion state of the selected flame shape.

Abstract: Apparatus for detecting flame or smoke, having a radiation detection tube enclosed in a housing, facing the exterior through a transparent window at one end of the housing, and having a radiation source proximate the other end of the housing and external the tube housing, with an optical path exterior of the housing from the radiation source to a reflector ring positioned in front of the transparent window and in a direction to deflect radiation from the radiation source through the transparent window to the radiation detection tube. The invention also includes a second internal radiation source optically coupled to the radiation detection tube for providing a reference radiation, which not only provides a comparison base for radiation received by the radiation detection tube from external radiation sources, but also provides a monitor function to evaluate the quality of the optical path through the window and to check the operation of the radiation detection tube and related circuits.

Abstract: A fail-safe system for monitoring a condition and activating controls in response either to the non-existence of that condition or the failure of any component in the system, in which a preliminary fail-safe oscillation train derived from sensing the condition is converted into a steady state indication of that condition, and a secondary fail-safe oscillation train is generated in a fail-safe way from said steady state indication for further transmission downstream for control purposes. In the context of flame monitoring, means associated with the preliminary oscillation train are provided for discriminating between separate flames and for time delay purposes.

Abstract: A fire detection system using optical fibers to transmit flame signals from a plurality of remote monitoring stations to a central detection and analysis station, the invention comprises a network of optical fibers which connect the monitoring stations to the central detection station for the purpose of transmitting incident analog optical, infrared and ultraviolet spectra to the central station for detection of fire conditions. The central detection and analysis station preferably includes a rotary scanner which scans each of the optical fibers, light from the fibers being dispersed by a prism associated with the scanner to allow detection of the various spectral components of the dispersed light by light sensitive semiconductors. The detected spectral components are then compared to known fire signal signatures which include flicker rate and spectral content information.

Abstract: An automatic fuel supply stopping device incorporated in fuel combustion equipment including a shut-off valve and a combustor. The automatic fuel supply stopping device comprises a fluid intercepting mechanism interposed in a channel through which the fuel supply to the combustor is supplied. A photosensor is adapted to detect fuel combustion in the combustor by radiation emitted from a thermosensitive luminous medium. The fluid intercepting mechanism alternately takes its first stable state or passage blocking state and is changed over, in response to an output from a sensor circuit, from the passage opening state to the passage blocking state.

Abstract: A test device for a multiple channel infra red detector utilizing photocells comprising an aperture plate mounted on the housing member of the detector. In the embodiment described a test lamp is mounted on a surface portion of the aperture plate in fixed relationship with two openings in the plate which are concentrically disposed about the two photocells. The test system utilizes the characteristic of the dual channel detector that the ratio of the response of each of the two cells to emissions in the infra red range (as received from a fire) is a certan value. The opening associated with one of the cells is larger in the path between the lamp and that cell so that more light energy impinges on it. The electrical energy to the lamp is increased until a level is reached where the ratio of the response of the one cell to the response of the other cell simulates the responses of the two when monitoring a fire. The warning system is triggered.

Abstract: A system for testing a wave guide arc detecting circuit for a microwave system is disclosed. Testing is accomplished by utilizing a pulsed laser source to generate pulses of optical energy which are used to simulate an electrical arc across the wave guide. The laser source is then positioned such that the pulsed output signal impinges upon the wave guide arc detector circuit to be tested. This is most advantageously accomplished by affixing the wave guide arc detector circuit to the wave guide in a fashion similar to normal operation. This enables the arc detecting circuit to view the end of the wave guide through the interior of the wave guide. The laser source is positioned such that the output pulse of the laser source impinges on the open end of the wave guide. The operational status of the wave guide arc detecting circuit is determined by measuring the elapsed time between the generation of the output pulse of the laser and the detection of the pulse by the arc detecting circuit being tested.

Abstract: This invention relates to a spectrophotometer which includes a burner adapted for burning a gaseous fuel and for atomizing a sample to be analyzed in a burner compartment, mechanical elements or electrical circuitry serving to periodically pass a beam of light through the burner compartment, a detector, electrical circuitry for energizing the detector during the period of absence of the beam of light through the burner compartment, said detector being adapted when energized to produce an electronic signal representative of the presence of a flame in the burner compartment; and control elements responsive to the electronic signal for controlling the feeding of fuel to the burner.

Abstract: This invention relates to control circuits of the type which continuously monitor their own performance so as to be self-checking, i.e., to produce a response whenever the system shows the absence of a condition being monitored or a change therein and also produces a response if the control system itself should become inoperative or otherwise malfunction.

Abstract: A flame detector for monitoring the flame of a burner including an electrically actuatable photo shielding element positioned between a photoelectric element and the flame. The normally transparent photo shielding element may be turned opaque on command for simulating a no flame condition of the burner. The resulting signal from the photoelectric element is compared with a predetermined signal level, when there is actually no flame, for testing the flame detector.

Abstract: In a multi-burner boiler or industrial furnace installation that uses pulverized coal for fuel and utilizes an oil pilot torch it has been difficult to sense and discriminate satisfactorily between safe and unsafe burner operation in these multi-burner arrangements. By using both a Si detector (visible light responsive) and a lead sulfide detector (infrared responsive) and selectively combining the signals therefrom, the best characteristics of both detectors are utilized to provide satisfactory flame sensing.

Abstract: In a flame-detecting apparatus for developing an electrical signal responsive to light, impinging on a light-responsive surface from a predetermined flame area, for example, in a combustion chamber, a convex lens member is disposed at a distance from the surface longer than the focal length of the lens member such that light impinging substantially perpendicularly to the lens member is converged then slightly diverged onto the light-receiving surface. An aperture-defining member is positioned approximately at a focal point of the lens member between the lens member and the light-receiving surface for only giving a light passage around a light axis of the lens member, the cross-sectional area of the light passage being smaller than that of the light-receiving surface so that extraneous light impinging obliquely on the lens member is prevented from passing to the light-receiving surface.