Abstract: A turbidity sensor is provided with a light source and a plurality of light sensitive components which are disposed proximate a conduit to measure the light intensity directly across the conduit from the light source and at an angle therefrom. The conduit is provided with a plurality of protrusions extending radially inward from the walls of the conduit to discourage the passage of air bubbles through the light beam of the sensor. The direct light beam and scattered light are compared to form a relationship that is indicative of the turbidity of the liquid passing through the conduit. The rate of change of turbidity is provided as a monitored variable.

Abstract: A dual beam spectrometer for conducting both turbidimetric and colormetric measurements includes a housing with a light source. The housing further includes source exit apertures that form light from the light source into a sample light beam and reference light beam. A sample cartridge for containing sample material to be measured is mounted in the housing in the path of the sample light beam. The spectrometer also includes a detector assembly for detecting the sample light beam and the reference light beam. The detector assembly includes a first detector that senses or detects sample light beam and a second detector that senses or detects the reference light beam. A sample light beam detection aperture tube is positioned in the housing between the sample cartridge and the first detector. Similarly, a reference light beam detection aperture tube is positioned between the sample cartridge and the second detector.

Abstract: A device is provided which passes light of preselected wavelengths through a fluid or vapor to be tested. The light is detected after it has passed through the fluid or vapor. Upon detection, a voltage is created which is proportional in amplitude to the detected light strength for each wavelength of light. These voltages are compared to produce a ratio which represents the condition of the fluid or vapor which is tested. When the ratio is outside of preselected boundaries, control signals are generated which may trigger alarms or otherwise respond to the condition.

Abstract: A fire alarm system which radiates light towards a smoke detecting space. Scattered light resulting from smoke that may exist in the smoke detecting space is judged by a receiver with respect to the type of smoke that may prevail in the space. The presence of a fire is judged by comparing the light that has been received with a set threshold level. The threshold level is set to different levels in accordance with the type of smoke detected.

Abstract: Light emitting diodes of a through beam photoelectric detector are positioned in a door hinged to a sensor body in which the photodetector diodes are located. The light emitting diodes and photodetector diodes are aligned to establish photoelectric sensors when the door is closed upon the body. A base provides a receptacle for attachment of the sensor, the base having a plug-in electrical terminal half for receiving the connector prongs of a second half of the connector carried by the body. The connector is symmetrical so that the sensor unit may be installed to the base in either of two operating positions spaced 180 degrees apart to enable the hinge to be located at either the right-hand or left-hand side of the sensor unit and of the stations to be sensed.

Abstract: A device is proposed for measuring the composition of fluids, in particular of constituents of exhaust gases from internal combustion engines, in which a light ray (32, 31) is used to irradiate the exhaust gas to be measured over the length of a measuring section (29) and is weakened or changed more or less, depending on the content of constituents. The light signal being received is advantageously registered by a measured length light receiver (18) which is shielded light-tight against the light emitting light source (14) and is evaluated in relation to the original light emission, in an evaluation circuit (26). In this simple way, accurate information is obtained of the exhaust gas clouding and of the loading of a fluid or gas with constituents which are optically active.

Abstract: An optical probe apparatus (10) is for testing physical properties of a fluid (F) such as turbidity. The apparatus comprises a probe assembly (16) removably insertable into the fluid. A photometric light source (12) generates light and fiber optic cables (14) transmits light to and from the probe assembly. Light entering the assembly is directed into the fluid, the light being absorbed or scattered by particles in the fluid as it passes therethrough. The amount of remaining light is sensed and a light output from the probe is produced whose intensity is a function of the amount of remaining light. A light detector measures the light output of the probe assembly and produces an indication of the absorbance or turbidity of the fluid.

Abstract: An ink concentration sensor maintains ink concentration in an ink jet printing system. The ink concentration sensor includes a transparent fluid chamber and an infrared light source for directing a beam of IR light at the fluid chamber. A first sensor is located for receiving IR light reflected from the surface of the chamber and providing a reference signal and a second sensor is located for receiving IR light transmitted through the chamber to produce a concentration signal. A circuit receives the reference signal and generates a corrected concentration signal.

Abstract: An evanescent wave liquid level sensor for measuring the density-compensated level of a liquid in a container. The sensor employs an eccentric core optical fiber fully immersed in the liquid to be measured. Light is injected into one end of the fiber. Some of the light will be lost due to evanescent wave losses. Changes in the ratio of the intensity of the input light and the reflected light are due solely to changes in the density of the liquid. Changes in the liquid density can then be used to compensate a liquid level measurement. Since the liquid temperature is related to its density, the sensor can also be used to measure changes in the liquid temperature.

Abstract: A gas detection device employs a tunable wavelength laser, modulated about an absorption line of a gas to be detected. By measuring the ratio of the fundamental to the second harmonic of the modulation frequency, the detection is independent of the optical path length. This permits an aimable device in which a laser beam is directed toward a remote surface, reflected thereby, and the reflected beam focused upon a detector. The presence of the gas to be detected in the space between the device and the reflective surface is thereby determined.

Abstract: Radiations of two different frequencies are transmitted through a fluid comprising a mixture of materials, wherein a radiation is absorbed in the range of the radiation absorption by one of the materials, and another radiation is not absorbed, and wherein the radiations operate with pulses of identical pulse repetition frequency and identical pulse intervals. The detected electrical signal from the monitored radiations passed through the fluid, the center frequency of which corresponds to the reciprocal value of the pulse interval, is filtered out with the aid of a filter. The concentration of the absorbing material in the fluid is measured from the amplitude changes of the filtered-out signal. By the use of filters, the bandpass ranges of which are respectively adapted to the occurring pulse repetition frequencies, and based on the interpretation of the measuring signal as a modulated signal, a high safety against noise signals is attained.

Abstract: An apparatus for liquid flow detection especially adapted for use with an IV administration set includes an energy beam emitter device and an energy beam detector device. A drip chamber is connected in flow communication with a fluid reservoir of the IV administration set. Fluid flow is directed through a drop forming orifice into the drip chamber and thence into a supply tube for the IV administration set. The energy beam emitter device produces a pair of parallel spaced beams which are directed across the free fall path of the fluid drops and to the energy beam detector device. As the drops enter and exit the energy beams, signals are generated by the detector device as a function of time and are fed to a microprocessor. Using this data and relationships developed with conventional mathematics, the diameter of each drop can be extrapolated. From the drop diameter, the drop volume can then be calculated and used with the time measurements to provide extrapolated outputs of flow-rate and total volume.

Abstract: Method and apparatus for determining accumulated film thickness at the inside diameter of a main stream conduit conducting a main stream of a flowing fluid by employing:a transparent shunt conduit to shunt from the main stream a sample stream of the process fluid,a reference light emitter and light detector at a reference section of the shunt where any appreciable film is removed, an upstream sample light emitter and detector opposed thereto,a common source of light so that respective emitters emit light beams of the same intensity, and means for determining concurrently analogs of light received by the detectors, whereby film thickness may be determined for the sample.

Abstract: Detection apparatus employs a plurality of conduits, a plurality of photosensors, and a laser in a multi-port forward-scattering geometry to detect particles for each of a plurality of spatial sections (S.sub.1, . . . S.sub.n) of an enclosure. The photosensors are provided in two sets arranged at two different scattering angles to discriminate smoke from other particulate matter in sample flows which flow along the conduits and intersect the laser beam. The sample flows are discharged into a plenum and removed from the plenum via a single manifold. The laser can be backed up by an auxiliary laser.

Abstract: The process for measuring the concentration of materials, wherein a radiation is absorbed in the range of the radiation absorption of the material, and another radiation is not absorbed, operates with pulses of identical pulse repetition frequency and identical pulse intervals. The detected electrical signal, the center frequency of which corresponds to the reciprocal value of the pulse interval, is filtered out with the aid of a filter. The concentration of the absorbing material is determined from the amplitude changes of the filtered-out signal. By the use of filters, the passband ranges of which are respectively adapted to the occuring pulse repetition frequencies, and based on the interpretation of the measuring signal as a modulated signal, a high safety against noise signals is attained.

Abstract: A turbidimeter includes a housing having a cavity with an inlet through which a fluid flows. Two emitters are alternately driven by an alternating signal having a given frequency to transmit modulated light beams through the fluid. Two detectors produce signals representing the intensity of scattered and unscattered light within the fluid. Each of these detector signals is processed to measure the level of the signal component at the given frequency. Such processing includes filtering and phase demodulataing the detector signals to produce a signal indicative of the levels of the component signals at the given frequency. The turbidity is calculated from the signal levels measured as each emitter is excited.

Abstract: A noise suppression system is described for use with a laser measurement system in which a beam sampler divides the laser beam into a signal beam and a sample beam. The signal beam is passed through an optical system before being received at the detector while the sample beam is received directly at the detector. The beam sampler is selected such that the received sample beam has a slightly greater steady-state intensity than the received signal beam. The detector circuitry includes two linear wideband photodetectors which produce respective signal and sample currents of opposite polarity. The sample photocurrent is subdivided into two component currents, one of which has substantially the same direct current (DC) value as the signal photocurrent. This component is combined with the signal photocurrent to cancel undesirable noise components in the original laser beam.

Abstract: A rotary stand (11) having a half-mirror (8) and a photodetector (10) mounted thereon, is continuously rotated around a first rotary shaft (A) passing through a sample (S), and set to a predetermined scattering angle. Simultaneously, a rotary reflecting mirror (7) is rotated at a predetermined angle to direct a reference li8ght (LR) to the half-mirror (8) at all times. The half-mirror (8) is also rotated at its own axis at a predetermined angle so that the direction of a scattering light (LS) at the light emitting side of the half-mirror (8) is identical with the direction of the reference lilght (LR). Accordingly, the reference light may be composed with the scattered light at an arbitrary scattering angle, enabling observation of the Doppler shift in the scattered light direction (FIG. 1).

Abstract: An apparatus and method which provides a measure of the asymmetry as well as the size of individual fluid borne particles. Laser-light scattering techniques are employed to obtain data on the particles, which is then compared to data on known particle shapes to ascribe an asymmetry factor to the particles.

Abstract: An improved transmissometer of the type which has a visible light source and is responsive to peak and mean spectral responses between 500 nm and 600 nm and optical assembly therefor contains a solid state light source preferably a light emitting diode. The light source emits a low level light beam that is split, part of which is passed through a gaseous sample then directed to a detector while the other part is directed to a second detector. Electronic components are provided to amplify the signal that has passed through the sample providing high gain, low noise amplification and use signals from the detectors to control the light source and determine opacity of the sample.

Abstract: The present invention utilizes the difference of light reception data generated based on the difference in length of substantial optical diffusion paths between a single light receiving point and a plurality of irradiation points, or between a plurality of light receiving points and a single irradiation point. According to the present invention, the inside information of substance based on the difference in length of the optical diffusion paths, may be measured. Even though measurements are made under different measuring conditions as to the part to be measured, the measuring time, etc., there may be obtained reliable measured data of the inside information with good reproducibility.

Abstract: A portable particle analyzer is compact and can determine the size, geometry and number of particles in a sample of fluid. A laser beam (15) intercepts the flow of fluid (17) at the first focal point of a parabolic mirror (11). Light is scattered and collected by radiation collectors (13) and low angle scattered radiation is detected in a second chamber (19) by reflection by an ellipsoid mirror (20) towards a radiation collector (21). Photomultiplier units (23) convert the radiation collected into electrical signals for analysis.

Abstract: Agglomeration or solubilization of particles of a suspension can be determined during a scanning sedimentation analysis of particle-size distribution by monitoring respective values of extinction determined in two successive scans or from one scan and a fixed light curtain at a common ratio h/t where h is the distance of the measurement by the light curtain from the surface of the suspension and t is the time at which the measurement is taken.

Abstract: In a double-beam photometer comprising a light source providing a light beam, detector means, a sample area, optical means for guiding the light beam as a measuring light beam through the sample area onto the detector means, means for guiding the same light beam as a reference light beam onto the detector means while avoiding the sample area, and chopper means disposed in a splitting location for splitting the light beam into the measuring light beam, which are combined into one path of rays in a recombination location, after the measuring light beam has passed through the sample area, with the splitting location and the recombination location being spatially close to each other. The chopper means has a single chopper which simultaneously effects the splitting and the combination of the measuring and reference light beams.

Abstract: A method for operating an optical smoke detector, wherein for smoke detecting purposes at least one light sensitive receiver within a detection chamber measures the useful scattered radiation which emanates from a volume unit within said chamber which is located in the intersecting area of the collimated field of view of said receiver and of the collimated beam of a light source within said chamber, said receiver sensing the scattered radiation caused by a contamination of said chamber or a second light sensitive receiver detecting the radiation reflected from a surface unit of said chamber, respectively, whereby measuring the reflexion radiation emanating from an illuminated surface unit within said chamber.

Abstract: A turbidity meter has a sensor unit supported in a fluid under test with a light source and at least two light sensors supported so that one light sensor is in line with the source to receive transmitted light and the remaining sensor or sensors are arranged to receive light scattered by the fluid. Both the source and the sensors have flow forming chambers connected to a source of pressurized fluid so that a thin layer of this fluid is caused to flow over lenses of the source and sensors to prevent deposition of material from the fluid under test. The signals from the sensors are digitized, and the intensity of the source is digitally controlled to maintain at least one of sensor signals within a suitable range, thus enabling operation over a wide range of turbidities, and automatic selection of turbidimetric and nephelometric modes of operation as appropriate.

Abstract: This specification discloses a particle measuring apparatus characterized by means for passing a particle to be examined to a portion to be examined. First applying means applies an irradiating light from a first direction to the portion to be examined, second applying means applies an irradiating light from a second direction differing from the first direction to the portion to be examined. First and second photometering means photomets the lights radiated from the portion to be examined by the application of lights to the particle to be examined, relative to the first and second applying means, respectively.

Abstract: The method and apparatus for measuring the particle concentration in a fluid that is passed between a reciprocally movable window and a single photodetector. A collimated beam of light is directed through the window and fluid to the photodetector. The window is moved from a first predetermined location to a second predetermined location to vary the light beam path length, thus enabling at least two different photodetector output signals. The ratio of the two signals provides the data needed to determine the particle concentration in the fluid.

Abstract: An improved transmissometer and optical assembly therefor contains a solid state light source preferably a light emitting diode. The ligh source emits a low level light beam that is split, part of which is passed through a gaseous sample then directed to a detector while the otehr part is directed to a second detector. Electronic components are provided to use signals from the detectors to control the light source and determine opacity of the sample.

Abstract: In an apparatus for determining the concentration of foreign substances in a stream of water, a liquid stream is derived from lines preceding and following the pipeline block for the process and each is pumped into a cell, a radiation source being associated with each of the cells, whose beams penetrate the cells and are delivered both to a first detector and to a second detector. A beam filter is placed in front of each of the detectors and divides the beams into two beams of different wavelengths. Between the beam source and the two cells a revolving chopper wheel is disposed which alternately deflects the beams of the radiation source into one and the other cell, while the electrical signals of the detectors are compared with one another by an electrical circuit and processed to an identifying signal.

Abstract: A method and apparatus for measuring the particle concentration of suspensions, especially suspensions having high particle concentration. Light is directed into the suspension, and light scattered by the particles, preferably back-scattered light, is detected at a first and a second position located at different distances from the position where the light is sent into the suspension. The concentration is then calculated asarctanh (E.sub.f /E.sub.n),or preferably ##EQU1## where E.sub.n is the detected light intensity at the first relatively near position and E.sub.f is the light intensity at the second relatively far position. The intensity of the light directed into the suspension is controlled by means of the relation E.sub.f .multidot.E.sub.n =1. The mean value of E.sub.f and E.sub.n is then compared with 1 in order to determine whether the calculated concentration corresponds to the concentration of the suspension being measured.

Abstract: The invention relates to monitoring equipment for smoke and/or fine particle emissions from fossil fuel systems, of the type where a beam of visible light is passed across a flue from a light source to a detector, a difference in the light intensity received by the detector from the known intensity of the source indicating absorption of light by smoke and/or fine particles in the flue, and the degree of difference indicating the level of smoke and/or fine particles. The objective of the invention is to provide monitoring equipment of the above type, of simpler, lower cost, more robust nature than has hitherto been provided. The objective is met by a construction comprising two units (1, 2) for location of opposite sides of a flue or chimney each unit comprising a light source, (L.sub.1, L.sub.2) a lens (4) and a light detector (D.sub.1, D.sub.

Abstract: Gases in the atmosphere are detected remotely using a Raman-shifted excimer/dye laser beam formed by passing an excimer/dye laser beam through a circulating-medium Raman-shifting cell which significantly increases the measurement repetition rate and allows for the production of an infinite number of different wavelengths for measurement. The Raman-active medium is continuously circulated so that the inputted laser beam passes through the Raman-active medium when the molecules of the medium in the optical path are at their ground energy level state. The Raman cell is then tuned to provide a first wavelength, preselected for nonabsorption by the gases to be detected, which is transmitted through the gases to be detected toward an object capable of reflecting the beam back. The Raman cell is also tuned to provide a second wavelength, preselected for being highly absorbed by the gases to be detected, which is then transmitted and similarly reflected.

Abstract: Humidity is measured by alternatively producing two laser beams of different wavelengths at each of which the second differential derivative of the light absorption spectrum of water molecules is zero, dividing each laser beam, passing one divided beam along an optical path of known length through air, passing the other divided beam along an optical path of the same length through vacuum, causing the divided beams to interfere so as to obtain an apparent difference in length between the two optical paths, this difference being due to the difference in the indices of refraction between air and vacuum, calculating the index of refraction of the air at each wavelength from this difference, and calculating the density of water molecules in the air, i.e. the humidity of the air, from the so-obtained indices of refraction.

Abstract: The arrangement for the transmission of laser light (9) exhibits a laser tter (1) and a receiver (2) for the laser light (9). In order that it should be possible to establish if the optical system (6) of the receiver (2) becomes dirty or an obstruction passes in front of this optical system, the laser receiver (2) is provided with a reference light source (12) disposed after the optical system (6). If the objective (6) becomes dirty or if an obstruction passes in front of the same, light from the reference light source (12) is scattered into the detector (7), so that an alarm indication can be given by a warning circuit (14).

Abstract: A system for detecting contaminant particles in a liquid, such as used for processing wafers during the manufacture of integrated circuits, distinguishes non-contaminant bubbles generally found in liquids from contaminant particles. The system provides a controlled laminar fluid flow of the liquid through a pipe, and the substantially spherical bubbles in the flow path are detected by symmetrically spaced photodiodes. The irregularly shaped contaminant particles are detected, whereas the presence of bubbles are negated by the detection system by virtue of the balanced photodiode assembly.

Abstract: A droplet size measuring apparatus of the forward scattering method, wherein particles to be measured in a scattering zone having a predetermined scattering path length are irradiated with parallel laser beams. The irradiated beams are scattered by the particles and the scattering beams are detected by the photodetectors arranged at predetermined scattering angles. The output of the photodetectors are input to an arithmetic operating unit, thus the intensity distribution I(.theta.) of the scattered beams is measured. The droplet size distribution n(D) is calculated from the intensity distribution I(.theta.) using the following equation:I(.theta.)=.intg.{I.sub.0 exp(-l.intg.c(D)n(D)dD..intg.i(D,.theta.+.theta..sub.

Abstract: Two photoelectric smoke detectors are arranged so that each smoke detector in turn verifies operation of the other smoke detector. Each smoke detector has a light source and a photodetector which is not directly illuminated by the light source. A smoke detection signal is issued when light from such a light source is scattered to the respective photodetector. The two smoke detectors are arranged so that a small amount of light from each light source illuminates the photodetector of the other smoke detector. A fault signal is issued when such a photodetector is not illuminated by the other light source.

Abstract: A system for transmission loss comparison permits enhanced accuracy over a wider dynamic range by providing a reference channel including a transmitter, receiver, and transmission path therebetween, and a sample channel, including a transmitter, receiver, and transmission path therebetween. A feedback arrangement is provided for adjusting the outputs of both of the reference and sample transmitters in relation to the signal output of the reference receiver, so as to produce a desired signal level of the reference receiver's output over a given dynamic range, so as to compensate for loss over the reference transmission path. In this way, a comparator connected to the outputs of the two receivers receives inputs that are compensated for effects of losses over the reference transmission path.

Abstract: The security apparatus is mounted to objects to indicate when a person or moving body is in the vicinity. Detection of movement or vibration is determined by air bubble movement in a liquid charged chamber. Light emitting means radiating from end placements of the chamber cause lateral reflections from the end edges of the bubble. Detecting apparatus senses the differential in received bubble edge illumination and activates security warning equipment when there is imbalance due to bubble movement. Bubble dimension changes due to temperature variations are nullified by balance sensing. Automatic sensitivity control by sensing ambient light or under timer control allows security maintenance over changing environmental backgrounds. Remote supervision by radio link is an embodiment. Security of the radio communication is maintained by a process of carrier frequency division used for self modulation of the carrier frequency signal.

Abstract: A particle detector includes a laser, a beam shaping lens, and a pair of mirrors which reflect the shaped laser beam back and forth between the mirrors a selected number of times in order to create a sheet of light or light net between the mirrors. The path of the beam is terminated by a beam stop which contains a photodiode to monitor beam intensity and thereby system alignment. Light scattered by a particle falling through the sheet of light is gathered and transmitted to a photodiode. A peak detector provides a measure of the peak intensity of light scattered by such a particle to a microprocessor, which counts the number of particles falling through the light net in a selected time interval. The microprocessor also uses the peak intensity to estimate the size of the particle.

Abstract: In order to eliminate equipment-generated fluctuations during the periodic determination of a quantity to be measured which is effected by forming the difference between a measuring signal which has been altered relative to a source signal by the measurement variable and a reference signal which has remained unaffected relative to the source signal by the measurement variable, a base signal level is determined for each measuring cycle as the difference between the reference level and a zero level in the absence of a source signal, subsequent to which each actual reference signal level and each measuring signal level is compensated with the previously determined reference signal level. By amplifying the compensated reference signals prior to difference formation and standardizing the signal difference to the base signal level, a high degree of accuracy may be achieved even if the attenuations of the measuring signal caused by the quantity to be measured are very small.

Abstract: The system and the method of the present invention tests the homogeneity of a solution utilizing a housing which includes a first chamber for a reference solution and a second chamber for a test solution. The housing also includes a pair of transducers spatially related to the first and second chambers for providing signals in accordance with incident lights. The housing also includes a light source which provides light equally to both chambers in a manner so the light passes through the solutions in both chambers to be incident upon the transducers. Circuitry connected to the transducers provide an output signal related to the quality of the test solution in accordance with the signals provided by the transducers.

Abstract: Concentration of a smoke emanating from a combustion engine is determined by projecting beams of light on the flow of smoke in directions traversing the flow of smoke, detecting intensities of beams of light which have traversed the flow of smoke with a light receiving device and calculating a cross-sectional image of the flow of smoke based on detection signals issued by the light receiving device.

Abstract: Method and apparatus for monitoring the purity of a liquid in a container by passing a laser beam divided into two portions with the first portion passing through a pair of quartz windows with the liquid in a container therebetween, and the second portion being directed through the two windows and the liquid, the first portion being detected to detect the amount of solid particles in the liquid, and the second portion being detected to determine changes in refraction index to obtain a recording of the purity of the liquid.

Abstract: An apparatus and method for determining the extinction of laser light through a fluid is disclosed. The fluid is passed in a conduit having a light transmissive window. A laser beam having intensity I.sub.1 is passed through the window into the fluid. A prong shaped probe having first and second probe sections is disposed in the fluid flow. The first probe section includes a beamsplitter at a distance d.sub.1 from the window for redirecting a portion of the beam onto a first photodiode array, to determine the beam intensity I.sub.2. The remaining portion of the beam tranverses a distance d.sub.2 and is directed through a prism onto a second photodiode array to determine its intensity I.sub.3. Based on the intensities I.sub.1, I.sub.2 and I.sub.3 and given d.sub.1 and d.sub.2, the extinction values E.sub.1 and E.sub.2 may be calculated. Fluid optical density may then be determined as a function of the extinction.

Abstract: The extinction coefficient of atmospheric aerosol is measured by an instrument in which a single light beam from a graybody source is alternately directed through two similar optical paths to a detector. Each optical path traverses an equal length region of ambient air. Aerosols are filtered from the ambient air region of one optical path .The detector measures the modulation of the incident radiation and its output is a function of the extinction coefficient of the ambient air under test. A second detector is used to monitor the beam power. Processing electronics compute the extinction coefficient of the ambient air under test from the detector outputs. The ambient air regions of the two beam paths are alternately filtered for improved performance.

Abstract: A power station boiler condensate water monitor employs a light-scatter cell for the detection of oil and/or particulates in the water. In order to determine background scatter levels, provision is made to alternatively pass clean water through the cell (FLUSH). The offset voltages obtained from the detector outputs when clean water is employed are compensated for differences in temperature between the boiler condensate water and the clean water before substraction from the detector outputs when boiler condensate water is employed. The monitor is capable of detecting oil levels of less than 2 parts per million.

Abstract: A particle detector includes a laser, a beam shaping lens, and a pair of mirrors which reflect the shaped laser beam back and forth between the mirrors a selected number of times in order to create a sheet of light or light net between the mirrors. The path of the beam is terminated by a beam stop which contains a photodiode to monitor beam intensity and thereby system alignment. Light scattered by a particle falling through the sheet of light is gathered and transmitted to a photodiode. A peak detector provides a measure of the peak intensity of light scattered by such a particle to a microprocessor, which counts the number of particles falling through the light net in a selected time interval. The microprocessor also uses the peak intensity to estimate the size of the particle.

Abstract: In a smoke detection system, smoke density in a sampling chamber is measured by flashing a strobe light through the chamber and sensing light flux emitted from the chamber and comparing it with light flux from the strobe light itself. The measurements are performed by peak detectors which load sample-and-hold circuits to provide steady signals. The two signals are combined in mathematical manner to compensate for zero-offset and rate error between the two signals. The combined and corrected output is used to actuate a visual alarm signal, such as a segmented bargraph display to indicate air pollution. The bargraph has programming pins for tapping off each individual bargraph segment to achieve plural preset alarm thresholds.