Abstract: An optical measurement system for obtaining information such as the absorption coefficient of a light-absorbing liquid, or a surface profile of an object immersed in a light-absorbing liquid having a known absorption coefficient. The system includes a light source that transmits light through the liquid, a detector that records an image of the light transmitted through the sample and a processor or other means adapted to analyze the intensity distribution found on the image to generate information about the sample.

Abstract: A gas analyzing apparatus includes a probe for measuring a concentration of sample gas flowing in a pipe by an optical measurement system. Influence of a thermal lens effect phenomenon is suppressed so that measurement accuracy is improved. The apparatus includes a probe tube disposed to cross a flow path of the sample gas in the pipe to introduce the sample gas flowing in the pipe to a predetermined hollow measurement region. A light emission portion and a light receiving portion for project measurement light to the measurement region in the probe tube and receive the measurement light after passing through the sample gas in the measurement region. A purge gas feed tube disposed in the probe tube supplies purge gas to a region between the optical system members and the measurement region, with a gap to the inner wall surface of the probe tube.

Abstract: A dual sensor fire detector includes a smoke sensor and a gas sensor. A source of radiant energy emits a beam which is formed into first and second beams. One beam is directed into a smoke sensing chamber. The other is directed to a gas sensor. Outputs from the smoke sensor and the gas sensor are combined to make a fire determination.

Abstract: Described herein are apparatuses for detecting an analyte in a liquid sample using optical time of flight spectroscopy. A handheld apparatus for remote real-time detection of Zn2+ in aqueous environments and methods for making and using the apparatus are also described herein.

Abstract: Provided is an optical measuring apparatus including a light irradiating unit that irradiates a sample flowing through a flow path with light, a light detecting unit that detects optical information emitted from the sample due to light irradiation by the light irradiating unit, and a rate information adding unit that adds a predetermined display corresponding to a flow amount of the sample per unit time obtained from the optical information to a waveform data graph obtained from the optical information.

Abstract: This invention concerns a fluorometer preferably combined with a thermal cycler useful in biochemical protocols such as polymerase chain reaction (PCR) and DNA melting curve analysis. The present fluorometer features a low heat-generating light source such as a light emitting diode (LED), having a one-to-one correspondence to each of a plurality of sample containers, such as capped PCR tubes in a standard titer tray. The fluorometer of the present invention further comprises an optical path between each LED and its correspondingly positioned container, and another optical path between each fluorescing sample within the positioned container and an optical signal sensing means. The instrument can be computer controlled.

Abstract: Disclosed are systems and methods for analyzing an oil/gas separation process. One disclosed system includes a flow path containing a fluid, a fluid separator coupled to the flow path and having an inlet for receiving the fluid and a discharge conduit for discharging the fluid after having undergone a separation process in the fluid separator, an optical computing device having an integrated computational element configured to optically interact with the fluid before the fluid enters the fluid separator and after the fluid exits the fluid separator and thereby generate optically interacted light, and at least one detector arranged to receive the optically interacted light and generate an output signal corresponding to a characteristic of the fluid.

Abstract: Values for one or more particle properties, such as an aerosol asymmetry parameter g, can be measured directly using a detector that measures scattered light. The detector can comprise two or more diffusers coupled to optical sensors responsive to scattered light that is incident on the surfaces of the diffusers. One or more weighing functions can be obtained based on diffuser geometry. In an example, the diffusers correspond to quadrants of a circular toroid.

Abstract: Method of estimating a level of fluid that is absorbed by a porous substrate, wherein fluid is absorbed by the substrate, wherein a light is arranged near the substrate such that it emits light rays directed to the substrate, wherein the light intensity of the light rays transmitted through the substrate changes under influence of the decrease of the amount of fluid that is absorbed by the substrate.

Abstract: An excitation component or arrangement can provide excitation to a moving object so that information is encoded in time variation of light emanating from the object. For example, in each of a sequence of segments, it can provide a respective non-binary excitation spectrum, and the spectra can be different with a non-interference-like transition between them; because the object emanates light differently in response to the different spectra, photosensing results can be obtained that include encoded information about the object. The non-binary spectra could be different intermediate intensities, such as different gray levels or different intensities of one color or could be different colors. The excitation can be provided in a pattern with non-interference-like transitions between regions, and object motion can also be controlled.

Abstract: An ultraviolet (UV) fluorometric sensor measures a chemical concentration in a sample based on the measured fluorescence of the sample. The sensor includes a controller, at least one UV light source, and at least one UV detector. The sensor emits UV light in a wavelength range of 245-265 nm from the light source through the sample in an analytical area. The UV detector measures the fluorescence emission from the sample. The controller transforms output signals from the UV detector into fluorescence values or optical densities for one or more wavelengths in the wavelength range of 265-340 nm. The controller calculates the chemical concentration of the chemical in the sample based on the measured fluorescence emissions.

Abstract: The present invention relates to compositions for use in refrigeration, air-conditioning, and heat pump systems wherein the composition comprises a fluoroolefin and at least one other component. The compositions of the present invention are useful in processes for producing cooling or heat, as heat transfer fluids, foam blowing agents, aerosol propellants, and fire suppression and fire extinguishing agents.

Abstract: A fuel contaminant sensor is provided. The fuel containment sensor includes a fluid reservoir having an inlet and an outlet. A light source for projecting a light beam through the fluid reservoir is disposed on the fluid reservoir. A light beam detector for receiving the light beam projected through the fluid reservoir is disposed opposite the light source. A controller is provided for activating the light source and for receiving an output of the light beam detector. An interruption of the light beam inhibits the light beam detector from receiving the light beam.

Abstract: An ultraviolet (UV) fluorometric sensor measures a chemical concentration in a sample based on the measured fluorescence of the sample. The sensor includes a controller, at least one UV light source, and at least one UV detector. The sensor emits UV light in a wavelength range of 245-265 nm from the light source through the sample in an analytical area. The UV detector measures the fluorescence emission from the sample. The controller transforms output signals from the UV detector into fluorescence values or optical densities for one or more wavelengths in the wavelength range of 265-340 nm. The controller calculates the chemical concentration of the chemical in the sample based on the measured fluorescence emissions.

Abstract: An optical system for acquiring fast spectra from spatially channel arrays includes a light source for producing a light beam that passes through the microfluidic chip or the channel to be monitored, one or more lenses or optical fibers for capturing the light from the light source after interaction with the particles or chemicals in the microfluidic channels, and one or more detectors. The detectors, which may include light amplifying elements, detect each light signal and transducer the light signal into an electronic signal. The electronic signals, each representing the intensity of an optical signal, pass from each detector to an electronic data acquisition system for analysis. The light amplifying element or elements may comprise an array of phototubes, a multianode phototube, or a multichannel plate based image intensifier coupled to an array of photodiode detectors.

Abstract: A fuel contaminant sensor is provided. The fuel containment sensor includes a fluid reservoir having an inlet and an outlet. A light source for projecting a light beam through the fluid reservoir is disposed on the fluid reservoir. A light beam detector for receiving the light beam projected through the fluid reservoir is disposed opposite the light source. A controller is provided for activating the light source and for receiving an output of the light beam detector. An interruption of the light beam inhibits the light beam detector from receiving the light beam.

Abstract: A pulse oximeter for measuring arterial oxygen saturation levels is provided. The pulse oximeter includes an LED signal generator for transmitting one or more light signals to a testing medium and a photodetector signal generator for processing at least a portion of the light signal generated by the LED signal generator into a photocurrent. The pulse oximeter further includes an integrated information transmission component for transmitting information corresponding to the pulse oximeter and which is integrated with the pulse oximeter without requiring additional wiring. A processing system within the pulse oximeter can generate a voltage to the integrated information transmission component to read the information stored in the component without causing the LED signal generator to generate a signal.

Abstract: A pathogen detector has a sample area for containing environmental air, a light source on one side of the sample area for directing a collimated beam of light through the sample air so that part of the light beam will be scattered by any particles present in the air while the remainder remains unscattered, and a beam blocking device on the opposite side of the sample area for blocking at least the unscattered portion of the beam of light and directing at least part of the scattered light onto a detector. The detector produces output pulses in which each pulse has a height proportional to particle size and a pulse height discriminator obtains the size distribution of airborne particles detected in the air sample at a given time from the detector output. An alarm signal is activated if the number of particles within a predetermined pathogen size range of around 1 to 7 ?m exceeds a predetermined normal level.

Abstract: An optical leak detector for use with a cooling system is described. The optical leak detector includes a light source, a light detector, and a conversion device. The light source is optically coupled to the light detector by way of an optical path. The light detector generates an electronic signal in response to light received from the light source. The conversion device, which is attached to the light detector, generates an electronic signal in response to the amount of light received from the light source. This electronic signal can indicate if a leak has occurred in the cooling system by the traversal of a entrapped gas bubble across the optical path formed by the light source and the light detector.

Abstract: The read head for luminometer includes a housing that encloses a cylindrical core. The housing has a through opening that aligns with a central passageway of the cylindrical core to define a confinement space. The housing and the cylindrical core are formed in two parts that diverge or converge with respect to each other under the influence of a manually controlled actuator member. When the housing parts and the core parts are in a closed convergent position an analytical line that extends through the housing and the core is maintained in a confined position within the confinement space of the housing and the core. Actuation of the housing parts and the core parts into a diverged open position opens the confinement space that accommodates the analytical line. The analytical line can thus be lifted away from the previous confinement space or reinstalled back into the open confinement space and then locked in place by an actuation of the housing parts into a closed converged position along with the core parts.

Abstract: An allergen particle detecting apparatus has a sample area through which environmental air is directed. A light beam is directed through the air sample so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. Light transmitted through the blocking device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level.

Abstract: A light beam is directed from a light source through an air sample so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. A light focusing lens in front of the light source is arranged to focus the unscattered part of the light beam onto the blocking device. Light transmitted through the blocking device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level. The signal may be used to activate filtering or air conditioning devices.

Abstract: An allergen particle detecting apparatus has a sample area through which environmental air is directed. A light beam is directed through the air sample so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. Light transmitted through the blocking device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level.

Abstract: An allergen particle detecting apparatus has a sample area through which environmental air is directed. A light beam is directed through the air sample so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the air sample is arranged to block all light except light scattered in a predetermined angular range corresponding to a predetermined allergen particle size range. Light transmitted through the blocking device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level.

Abstract: A testing device for qualitatively or quantitatively sensing an electrochemical or analogous reaction at the surface of a test strip (46), the current flowing or charge accumulated at the test strip being processed by electronics (50) to generate a current signal suitable for activating a display (52) typically in the form of a thermochromic layer.

Abstract: A device is disclosed for measuring light scatter by particles (3) suspended in a carrier medium with a view to ascertaining the density, size or size distribution of the particles. The device comprises: at least one light source (8) which directs light onto a light-scattering center (2) in the carrier medium with the suspended particles (3); a receiver (4) to pick up a portion of the scattered light from the light-scattering center; and an evaluating device connected downstream of the receiver (4). The invention provides for an elongated detection chamber bounded radially around its central axis by the wall of a housing (1) which also acts as a duct for the through-flowing carrier medium with the suspended particles (3). Each light source (8) is mounted on the wall of the housing (1) and points toward the central axis of the detection chamber.

Abstract: An improved method of monitoring particulates in stacks or ducts utilizes transmissometer/particulate monitor of the type which has an optical assembly containing a solid state light source of visible light such as a light-emitting diode or a solid-state laser. The light source emits a collimated beam that is split, part of which is focused onto a reference detector that monitors the intensity of the light source, while the other part is directed to a beam-steering apparatus that causes the beam to accurately pass through a gaseous sample to a desired location such as a retro-reflector. A position-sensing detector is used in a closed-loop manner to control the beam-steering apparatus. The ratio of the total energy of the detected light beam, relative to the reference detector output, is used to determine the opacity of the gaseous sample for the purpose of providing a basis for correlation to particulate loading of that portion of the particulates that are of a size comparable to the wavelength of light.

Abstract: A device and a related method of operation of the device for continuously monitoring the progress of a steeping beverage during the steeping process is disclosed which provides an indication to the user when the steeping beverage has reached an adjustable, desired level of steeping to thereby enable the making of a consistently steeped beverage without requiring the steeping operation to be timed or otherwise closely monitored. The device optically monitors the steeping beverage by using a photo diode to detect light from an LED which passes through a fixed measurement aperture immersed in the steeping beverage. By determining when the passage of light through the measurement aperture has decreased to a predetermined level indicative of both the color and the strength of the steeping beverage, an alarm may be provided to indicate that the beverage has steeped to precisely the strength desired.

Abstract: In a light scattering smoke sensor of the present invention, a first diaphragm portion is disposed just aheat of a light receiving device, and a second diaphragm portion is disposed ahead of the first diaphragm portion. A gap between the first and second diaphragm portion is a smoke introducing portion which introduces smoke to a smoke detecting space via a gap between labyrinth members and the second diaphragm portion.

Abstract: An allergen particle detecting apparatus has a passageway through which environmental air is directed. A light beam is directed across the passageway so that portions of the beam will be scattered if any particles are present in the path of the beam. A beam blocking device on the opposite side of the passageway blocks any non-scattered portion of the beam while transmitting any scattered portions of the beam along a light path in the apparatus. Any light scattered by allergen size particles will be traveling in a predetermined angular range, and a pinhole device is positioned in the light path so as to transmit only light traveling in that angular range. Light transmitted through the pinhole device is detected by a light detector and an alarm output signal is produced if the detected amount of light is above a predetermined level.

Abstract: The present invention describes an optical technique for analyzing undiluted, multi-phase fluid flows as typically encountered inside reactor vessels or flow lines in the chemical industries. In particular the technique uses a pulsed, coherent light source and measures the back-scattered light collected over a wide scattering angle. A light beam is relayed via a set of lenses down a long probe tube, through a window at a probe tip to illuminate the material that is passing past the window. The light beam is pulsed to "freeze" the motion of the particles streaming past the window. The backscattered light is collected by the same set of optics and is focused on the front surface of a CCD chip.

Abstract: The quality of the laying of a silicone string for sealing purposes, for example between the crankcase and the sump of an internal combustion engine is controlled by a robot carrying a laser-meter head for measuring distances by reflection.

Abstract: A measuring instrument and a method of measuring including providing an illumination arrangement having a plurality of independent illumination sources, a specimen region for conducting a specimen illuminated by the illumination arrangement, a measuring arrangement detecting radiation influenced by the specimen in the specimen region, the illumination arrangement having a plurality of independent aluminum sources which are energized by separate leads and separate switch elements that are operable to selectively operate either individually or in common for a linearity check.

Abstract: An apparatus for preventing blocking of a measuring head intended for carrying out measurements on substances suspended in a flowing medium. A light beam is transmitted from a radiation source with a determined intensity which is essentially constant during the measuring process. the intensity of the radiation radiated from the medium is indicated with the aid of at least one radiation indicator. The electrical output signal of the radiation indicator is sent for evaluation to a signal processing device. An open measuring channel has two mutually opposing edges which are intended to be placed along the direction of medium flow. Radiation from the radiation source is emitted from the one edge and received at the other. Placed in connection with the measuring channel are radiation-conducting elements which are placed as close as possible to the outer part of the edges. All of the junctions between surfaces of different extension in the vicinity of the measuring channel are gently rounded.

Abstract: An apparatus and method for measuring a bodily constituent such as glucose or cholesterol by analyzing a sample taken from the body such as blood, saliva or urine. The sample is placed on a test strip inserted into the test block portion of the apparatus where the portion of the sample containing the constituent desired to be measured reacts with a chemical reagent. Products of this reaction have an absorbance/reflectance characteristic which is mathematically related to the concentration of the constituent in the bodily sample. The reflected light is absorbed by a photodiode and the output of the photodiode converted to a digital form where a microprocessor can calculate the concentration of the constituent using the mathematical relationship between the reflected light and concentration stored in memory means of the apparatus.

Abstract: Disclosed is a method and apparatus for measuring particles in a fluid by irradiating the fluid containing the particle with a laser beam and deriving particle characteristics such as diameter and size distribution from the intensity of the light scattered by the particles. Based on the value of the output of a photomultiplier used to detect the scattered light, it is determined whether a particle is a fine particle, which is a particle with a photoelectron pulse count that does not exceed a prescribed value, or a large particle, and these particles are counted separately. Fine particles are processed using photon counting, and large particles are processed by an analog process.

Abstract: Continuous monitor to determine effective performance of a flocculant used to dewater a sludge stream, in which a voltage waveform of water clarity, generated by a sensor opposed to a light beam transmitted across the stream, is digitized by a comparator; the comparator is insensitive to sludge flow rate.

Abstract: A method and apparatus for accurate low noise demodulation of a modulated multi-signal input waveform. The multi-signal input waveform includes a plurality of sequential signal pulses, each pulse having a first adjacent background signal immediately preceding it and a second adjacent background signal immediately following it in time. The invention provides apparatus for synchronously separating the sequential signal pulses and apparatus for synchronously demodulating each sequential signal pulse. The separating apparatus separates each sequential signal pulse together with its adjacent background signals into one of a plurality of channels according to the sequence order of the pulse. Once the sequential signal pulses are separated into separate channels together with their background signals, the demodulating apparatus in each channel averages the first and second adjacent background signals for each pulse to yield an adjacent average background signal.

Abstract: The visually observable information is expressed in quantitive form according to an arrangement wherein there is firstly detected the distribution, size, shape and similar characteristics of objects appearing essentially in one level or plane of the sample and deviating visually from their environment. This detection is carried out by forming an image of the primary physical object on a light sensitive detector using known optic means, such as a microscope, in order to code the random information into a digital form, and thereupon the results of detection, that is the information thus brought into digital form, is transferred for further analysis to a computing and registering unit, such as a special purpose or process computer. Preferably, the detector unit comprises an array or matrix of light sensitive elements, such as photo-transistors.

Abstract: A controller including a processor is coupled to a transceiver head pair respectively operative as a transmitter and as a receiver of infrared energy to controllably project a beam of infrared energy therebetween through a projected region. The controller is operative to de-sensitize the beam against potential electrically interferring effects present along the beam path. Plural alarm thresholds are operator selectable to provide enhanced confidence detection, and particularized signal indications are provided to readily and quickly identify possible alarm and trouble conditions.

Abstract: A system and an associated process are described for the determination of grain size distribution of particles in suspension. The suspension is settled in a settling tank and optical density measurements of the suspension are taken and from this the grain size distribution is determined. According to the invention, the suspension is homogenized by circulating it in the settling tank, then circulating is stopped and the optical density is repeatedly measured in the settling tank on at least three points with deviating spacings. The equipment described is a settling tank (1) for the suspension, a device for the measurement of optical density in the settling tank (1) and a computing unit calculating the grain size distribution from the optical density values measured. The settling tank (1) is equipped with a means for the circulation of the suspension and there are at least three measuring heads (2,3,4,5,6) along the settling tank (1) sensing the optical density.

Abstract: An apparatus and method which provides a measure of the size distribution of particles dispersed in a fluid based upon an optimum combination of CLS measurements and DLS measurements. The measurement is characterized by relatively high resolution particle sizing. DLS data representative of the autocorrelation function, or power spectrum, of the detected intensity of scattered light for m measurement conditions of a sample, is optimally combined with CLS data representative of the average total detected intensity of scattered light for n measurement conditions, to provide an angle-independent, high resolution size distribution v(r), where m.gtoreq.1, n.gtoreq.0, m+n.gtoreq.2, and at least two of the measurement conditions are different. The size distribution may be expressed in terms of the continuous function v(r) or the histogram v, and may represent distributions weighted by mass, volume, number, surface area, or other measures.

Abstract: Apparatus for detecting contaminants, including emboli, in a blood sample prior to blood cell analysis, wherein fluid density sensors are arranged on opposite sides of a fluid segmenting valve to provide electrical signals indicative of the degree of optical opacity of the fluid flowing through the sensors. The derived signals are compared against a diluent reference level signal to provide resultant signal outputs indicating the presence or absence of emboili or other contaminants within the segmented portion of fluid.

Abstract: In a laser-optical arrangement for producing signals by light scattering, obscuration or reflection, from flowing particles and/or groups of particles, which are recorded, as time-dependent voltage/current fluctuations, by means of a photodetector (9) via appropriate imaging optics (7,8,18), assignment to the degree of dispersion of the flowing system is based on a subsequent measurement (10) of the root-mean-square value, and, according to the invention, the sample stream (1) is separated from a transmitter (6,7,18) and a receiver (8,9,10) by an enveloping stream (4), and the transmitter side consists of an individual light-transmitting fiber (7) provided with a means for parallel or focused emergence of a light bundle having a diameter of the order of magnitude of the particles and/or groups of particles.

Abstract: A device for producing a digital representation of an analog signal in apparatus for use in analyzing samples of biological material. The apparatus conducts such analysis by optical techniques, whereby an analog signal is generated which corresponds to the strength of a light component impinging a light responsive element.

Abstract: A fiber optic probe having a sealed, cylindrical housing closed at one end by a transparent window and at the opposite end by a wall through which a plurality of optical fibers extend toward the window. Adjacent the window the fibers are radially and circumferentially spaced about the axis of the housing and converge along lines which intersect one another at a common point on the housing axis that is adjacent or beyond the outer surface of the window. At least one of the fibers transmits light from a source through the window to illuminate a zone of a fluid sample, whereby particles present in such zone scatter light therefrom to the remaining fibers for transmission through the probe housing to light detecting and measuring apparatus.

Abstract: An apparatus and method which provides a measure of the size distribution of particles dispersed in a fluid based upon an optimum combination of CLS measurements and DLS measurements. The measurement is characterized by relatively high resolution particle sizing. DLS data representative of the autocorrelation function, or power spectrum, of the detected intensity of scattered light at a plurality of angles about a sample, is optimally combined with CLS data representative of the average total detected intensity at those angles, to provide an angle-independent, high resolution size distribution v(r). The size distribution may be expressed in terms of the continuous function v(r) or the histogram v, and may represent distributions weighted by mass, volume, number, surface area, or other measures.

Abstract: Smoke density measuring apparatus comprising a duct (1) through which the smoke passes, a light source (4) and a photodetector (6) located on opposite sides of the duct adjacent openings (2,3) in the side walls of the duct so that the source (4) directs a beam of light across the duct through the openings to the photodetector (6), a gas supply (10) associated with the openings (2,3) in the side walls of the duct so that gas flows through each opening into the duct, gas flow control valve (13) for varying the rate of flow of gas through said openings, sensor (17) for monitoring the rate of flow of smoke through the duct, and a control circuit (FIG. 4) for controlling the gas flow control valve (13) in a manner dependent on operation of the sensor (17) so that the rate of flow of gas through the openings is reduced when the rate of flow of smoke falls below a predetermined value. The control circuit (FIG.

Abstract: In a photoelectric smoke detector, a radiation source is driven intermittently by a control circuit and the radiation influenced by smoke particles, for instance scattered radiation, is picked up by a radiation receiver. The signal of the radiation receiver is transmitted to a signal processing circuit which is transmitted to a signal processing circuit which is simultaneously regulated by the control circuit. The signal processing circuit comprises a phase sensitive circuit which reverses or inverts the received signal according to the phase of the signal of the control circuit and transmits the thus modified signal to an integrating circuit. The integrating circuit controls a display circuit by means of its integrated output signal. The display circuit can, for instance, output an alarm signal when the integrated signal, i.e. the smoke intensity, exceeds a prescribed threshold value or can display the smoke intensity.

Abstract: In a scattered radiation smoke detector (D) the energy supply from the evaluation unit (A) and the signal returned thereto take place exclusively optically by means of radiation conducting elements (L.sub.1, L.sub.2) and all electrical components are situated in the evaluation unit (A) remote from the smoke detector (D). An approximately parallel transmitting or reception zone of small diameter is generated by collimating devices (4, 6) disposed at the ends (3, 8) of the optical conductors and thereby the interference radiation level in the smoke detector is reduced and the sensitivity increased. Since the smoke detector (D) comprises no metallic components, it is insensitive to temperature and corrosion and is especially well suited for application in environments subject to the danger of explosion and electrical interference.