EP1535049A2 - Procede et appareil de controle de particules s'ecoulant dans une pile - Google Patents

Procede et appareil de controle de particules s'ecoulant dans une pile

Info

Publication number
EP1535049A2
EP1535049A2 EP03764014A EP03764014A EP1535049A2 EP 1535049 A2 EP1535049 A2 EP 1535049A2 EP 03764014 A EP03764014 A EP 03764014A EP 03764014 A EP03764014 A EP 03764014A EP 1535049 A2 EP1535049 A2 EP 1535049A2
Authority
EP
European Patent Office
Prior art keywords
light
scattered
measurement
phase
detector
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03764014A
Other languages
German (de)
English (en)
Inventor
Michael Rigby
Michael Wakefield
John Michael Blackwell
Victor Frederick Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PCME Ltd
Original Assignee
PCME Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by PCME Ltd filed Critical PCME Ltd
Publication of EP1535049A2 publication Critical patent/EP1535049A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G01N21/532—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke with measurement of scattering and transmission
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
    • G01N21/534—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke by measuring transmission alone, i.e. determining opacity
    • G01N2021/536—Measurement device mounted at stack
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
    • G01N21/274—Calibration, base line adjustment, drift correction

Definitions

  • This invention relates to the field of monitoring particles flowing in a stack.
  • the particles When light interacts with particles, the particles may reflect, refract, diffract or absorb the light, the nature of the interaction depending on the size, refractive index and surface profile of the particles and the wavelength of the interacting light.
  • the light will undergo Rayleigh scattering and a proportion of the light may be redirected in all directions.
  • a proportion of the scattered light is redirected in the forward direction within well-defined angular lobes. This phenomenon is known as forward light scattering or Mie scattering.
  • classical geometric optics begin to dominate.
  • Particle monitors that use forward light scattering techniques can, in general, be divided into two different categories: in-line and out-of-line.
  • An in-line system utilises a light source, an interaction volume and a detector system on a common optical axis whereas the out-of-line approach places the detector system to one side of the light source axis.
  • Readings from prior-art monitors may be affected by the harsh conditions that are prevalent in many stacks. For example, probes using glass-fibres cannot operate above 350°C- 400°C and fibres based on sapphire, which may be able to operate at those temperatures, are very expensive.
  • a particular disadvantage of some prior art designs is that, although they provide mechanisms for checking the calibration of a probe, they do so by moving one or more parts of the system that is to be calibrated in a way that may cast doubt on the reliability of the calibration measurements.
  • a particle monitor for monitoring particles flowing in a stack comprising: (i) a light source for generating a measurement beam on a first side of the particle flow; (ii) an optical system for directing the measurement beam towards a second side of the particle flow without the measurement beam scattering from the particles, (iii) a reflector arranged to reflect the measurement beam back towards the first side of the particle flow, (iv) an optical system for directing the measurement beam into the particle flow such that light from the measurement beam is scattered by the particles; and (v) a scattered-light detector for detecting, on the first side of the particle flow, the scattered light.
  • an installation comprising a stack and such a particle monitor installed in the stack.
  • a method of monitoring particles flowing in a stack comprising: (i) generating a measurement beam on a first side of the particle flow; (ii) directing the measurement beam towards a second side of the particle flow without the measurement beam scattering from the particles, (iii) reflecting the measurement beam back towards the first side of the particle flow, (iv) directing the measurement beam into the particle flow such that light from the measurement beam is scattered by the particles; and (v) detecting, on the first side of the particle flow, the scattered light.
  • Such a ⁇ reflective' probe has several advantages.
  • One of the greatest difficulties in designing a monitor is accommodating the high temperatures experienced when the monitor is inserted into a hot stack.
  • sensitive parts of the monitor may be positioned outside the stack, thereby eliminating the need for significant (or preferably any) cooling or other special measures.
  • more bulky parts of the probe may also be located outside the stack; indeed, only minimal optics, in particular the reflector and focusing lens, need to be inside the stack.
  • the folded beam/probe arrangement removes the electronics from the heat of the stack. It is not necessary to use an optical fibre to guide light in the monitor.
  • the scattered light detector and the light source are housed in a common housing.
  • Such an arrangement is more convenient than, for example, the source and detector being arranged independently on opposite sides of the stack (an arrangement which is likely to require significantly more alignment) .
  • the measurement beam is directed through a tube to the second side of the flow. Provision of tube ensures that the measurement beam does not impinge on flowing particles prior to reflection from the reflector.
  • the tube may also provide a convenient means of supporting the reflector in the stack.
  • the light source, the optical system for directing the measurement beam, the reflector, and the scattered-light detector are housed in a common housing; that is, in one or more chambers in a single unit.
  • a common housing allows the monitor to be installed in one piece in a stack, significantly reducing the amount of alignment and calibration required.
  • the reflector may comprise a prism.
  • any other suitable form of reflector such as a retro reflector comprising a mirror (for example a retro-reflecting corner-cube) may be used.
  • a particle monitor for monitoring particles flowing in a stack comprising: (i) a light source for generating a measurement- phase beam; (ii) an optical system for directing the measurement-phase beam into a scattering zone in the particle flow; (iii) a transmitter window, arranged between the optical system and the scattering zone, through which the measurement- phase beam passes, the transmitter window being exposed to contamination by the particle flow; (iv) a scattered-light detector for detecting light scattered, from the measurement- phase beam, by the particles as they flow in the scattering zone; (v) a receiver window, arranged between the scattering zone and the scattered-light detector, through which the scattered light to be detected passes, the receiver window being exposed to contamination by the particle flow; (vi) a light source for generating a compensation-phase beam; (vii) a reference detector for detecting the compensation-phase beam and (viii) an optical system for directing the compensation-phase beam from the light source through the transmitter window and the receiver window to the reference detector, where
  • a method of monitoring particles flowing in a stack comprising: a measurement phase in which: (i) a measurement-phase beam is generated by a light source; (ii) the measurement-phase beam is directed into a scattering zone in the particle flow; (iii) the measurement-phase beam passes through a transmitter window, the transmitter window being exposed to contamination by the particle flow; (iv) light is scattered, from the measurement- phase beam, by the particles as they flow in the scattering zone, (v) the scattered light passes through a receiver window, the receiver window being exposed to contamination by the particle flow, and (vi) the scattered light is detected by a scattered-light detector; and a compensation phase in which (a) a compensation-phase beam is generated by a light source and (b) the compensation-phase beam is directed through the transmitter window and the receiver window to a reference detector; wherein, the measurement-phase beam and the compensation-phase beam pass through substantially coincident and co-extensive regions of the transmitter window and the scattered light and the
  • the monitor may be operated in a compensation phase in which the reference beam passes through the same parts of the transmitter and receiver windows as the measurement-phase beam and the scattered light in the measurement phase.
  • any contamination of the windows will be detected as a reduction in signal detected at the reference beam detector.
  • Some contamination of the probe may then be tolerated; for example, if the reference signal drops by only 5% then measurements may still be taken by assuming that the amount of scattered light detected will also be reduced by 5% and increasing measured values accordingly.
  • the transmitter window will generally be the last optical surface that the measurement beam passes through before reaching the scattering zone and the receiver window will generally be the first optical surface that the scattered light passes through after leaving the scattering zone because those optical surfaces will generally be the surfaces that are exposed to contamination by the particle flow. Preferably, all other optical surfaces are sealed behind those surfaces and are safe from contamination. As the measurement beam and the reference beam both pass through the same, and only the same, areas of the optical surfaces that are exposed to contamination, contamination-check measurements will be more reliable than in prior art devices.
  • the transmitter window is a transparent optical surface.
  • the receiver window is a transparent optical surface.
  • Either window may, however, be associated with a filter or other means of reducing its transparency.
  • Light here includes the electromagnetic spectrum from ultra-violet through to near-infra-red wavelengths.
  • One or both of the light sources may be lasers.
  • the light source for generating the measurement-phase beam and the light source for generating the compensation-phase beam are the same light source.
  • the reference detector is also the scattered-light detector.
  • the optical system for directing the compensation-phase beam comprises a means for diverging the compensation-phase beam so that it spreads across the regions of the transmitter window and/or receiver window through which the scattered light passes.
  • a convex lens or any other suitable means for spreading the beam out radially to cover that region may be provided.
  • the monitor is arranged such that the intensity of the compensation-phase beam is varied to provide a check on the calibration of the probe.
  • the calibration check is a span check, in which the signal output span of the probe is checked.
  • the same light source is used to generate the measurement-phase beam and the compensation-phase beam
  • the scattered-light detector is also the reference detector and that detector is in the same position when the 'apparatus is in a measurement configuration as when it is in a check configuration.
  • Using the same light source and the same detector and keeping the detector in the same position in the measurement phase and the check phase is particularly advantageous for calibration measurements because it means that the calibration is likely to be significantly more reliable.
  • no parts of the monitor through which the measurement beam or the reference beam pass are altered between the measurement phase and the check phase.
  • the check phase may be a compensation phase or a calibration-check.
  • the monitor may give a signal indicative of mass concentration of the particle flow.
  • the monitor may give a signal indicative of particle sizes in the particle flow. Mass concentration and particle size are two important parameters of particle flow.
  • a particle monitor for monitoring particles flowing in a stack comprising: (i) a light source for generating a normal-mode measurement-phase beam; (ii) an optical system for directing the normal-mode measurement-phase beam into a scattering zone in the particle flow; (iii) a scattered-light detector for detecting light scattered, from the directed normal-mode measurement-phase beam, by the particles as they flow in the scattering zone; (iv) a receiver window, arranged between the scattering zone and the scattered-light detector, through which the scattered light to be detected passes, the receiver window being exposed to contamination by the particle flow; (v) a light source for generating a calibration-mode measurement-phase beam; (vi) a reference detector for detecting the calibration-mode measurement-phase beam and (vii) an optical system for directing the calibration-mode measurement-phase beam from the light source through the receiver window to the reference detector, wherein the optical system for directing the normal-mode measurement-phase beam and the optical system for directing the calibration-mode measurement
  • a method of monitoring particles flowing in a stack comprising: a normal-mode measurement phase in which: (i) a normal-mode measurement-phase beam is generated by a light source; (ii) the normal-mode measurement-phase beam is directed into a scattering zone in the particle flow; (iii) light is scattered, from the measurement beam, by the particles as they flow in the scattering zone, (iv) the scattered light passes through a receiver window, the receiver window being exposed to contamination by the particle flow, and (v) the scattered light is detected by a scattered-light detector; and a calibration-mode measurement-phase in which (a) a calibration-mode measurement-phase beam is generated by a light source and (b) the calibration-mode measurement-phase beam is directed through the receiver window to a reference detector; wherein, the scattered light and the calibration-mode measurement-phase beam trace the same optical path through all optical elements between the scattering zone and the scattered- light detector, such that changes in intensity detected by the reference detector provide a means to calibr
  • Such an arrangement makes possible a calibration check that provides a very good indicator of the calibration of the probe because the calibration-mode measurement-phase beam and the scattered light pass along the same optical path through all optical elements between the scattering zone and the scattered- light detector. It is particularly advantageous that this can be achieved without moving those optical elements.
  • the light source contains a means for expanding the beam (such as a diverging lens or any other means of providing a wide beam) , a converging lens and a central stop, being arranged such that the calibration-mode measurement-phase beam is expanded in diameter and passes through the converging lens and such that parts of the beam outside the radius of the stop are focused onto the scattering zone.
  • a means for expanding the beam such as a diverging lens or any other means of providing a wide beam
  • a converging lens and a central stop being arranged such that the calibration-mode measurement-phase beam is expanded in diameter and passes through the converging lens and such that parts of the beam outside the radius of the stop are focused onto the scattering zone.
  • the reference beam may be focused on the scattering zone in a beam the shape of a hollow cone and the hollow cone may be arranged such that it is a back projection of light scattered from the scattering region.
  • the light source, converging lens and central stop are preferably arranged such that the calibration-mode measurement- phase beam is brought to a focus in the scattering zone and then diverges at all angles between 1 degree and 8 degrees.
  • the monitor further comprises a light source for generating a calibration-mode compensation-phase beam and an optical system for directing the calibration-mode compensation- phase beam from the light source through a transmitter window and the receiver window to the reference detector, the optical system being arranged such that the calibration-mode compensation-phase beam and the calibration-mode measurement- phase beam pass through substantially co-incident and coextensive regions of the transmitter window and the receiver window, such that changes in intensity detected by the reference detector provide an indication of contamination of the transmitter window and/or the receiver window.
  • the method further comprises a calibration mode compensation phase in which (i) a calibration- mode compensation-phase beam is generated, (ii) the calibration- mode compensation-phase beam is directed through a transmitter window and the receiver window to the reference detector; wherein, the calibration-mode measurement-phase beam and the calibration-mode compensation-phase beam pass through substantially co-incident and co-extensive regions of the transmitter window and the receiver window, such that changes in intensity detected by the reference detector provide an indication of contamination of the transmitter window and/or the receiver window.
  • the optical system for directing the calibration-mode compensation-phase beam comprises a means for diverging the calibration-mode measurement-phase beam, such that the calibration-mode compensation-phase beam spreads across the regions of the transmitter and/or receiver window through which the scattered light passes.
  • all optical elements between the scattering zone and the scattered-light detector are sealed behind the receiver window such that those elements are safe from contamination by the particles.
  • the same light source is used to generate the measurement beam and the reference beam.
  • the scattered-light detector is also the reference detector.
  • an air buffer is provided in front of the transmitter window and/or the receiver window.
  • a circularly symmetric air curtain is provided at the windows.
  • an air buffer is provided in front of the transmitter window and/or the receiver window.
  • a moveable optics holder is provided for inserting and removing optical components to change between normal and calibration modes and/or measurement and compensation phases.
  • the optical components may be pivotally mounted such that they may be swung into the measurement beam.
  • the optical components are mounted on a rotatable carousel.
  • the insertion is controlled automatically and remotely, for example by pneumatics or electronics.
  • the reference beam will generally be of a much higher intensity than any scattered light.
  • a particle monitor for monitoring particles flowing in a stack, comprising: (i) a light source for generating a measurement beam; (ii) an optical system, for directing the measurement beam into a scattering zone in the particle flow; (iii) a transmitter window, through which the measurement beam passes before it reaches the scattering zone; (iv) a scattered-light detector for detecting light scattered, from the measurement beam, by the particles as they flow in the scattering zone; (v) an element that acts as the smallest stop aperture between the scattering zone and the scattered-light detector, that smallest-stop element and the transmitter window being in line-of-sight of each other, and (vi) an optical system that prevents light scattered by the transmitter window and passing through the smallest stop aperture from reaching the scattered-light detector.
  • a method of monitoring particles flowing in a stack comprising: (i) generating a measurement beam; (ii) passing the measurement beam through a transmitter window; (iii) directing the measurement beam into a scattering zone in the particle flow; (iv) preventing light that is scattered by the transmitter window, and that passes through the smallest stop aperture between the scattering zone and a scattered-light detector, from reaching the scattered-light detector; (v) detecting, at the scattered- light detector, light scattered from the measurement beam by the particles as they flow in the scattering zone.
  • the smallest stop aperture is the region (which may be a transparent solid or a hole) whose spatial extent limits the maximum angle at which light is scattered from the scattering zone and reaches the scattered-light detector.
  • the scattering zone is long.
  • Such an arrangement has the advantage that any inhomogeneities in the particle flow are averaged out because light is scattered from all parts of the scattering zone.
  • a long scattering zone will generally result from small scattering angles.
  • a particular problem of small scattering angles is that light scattered from contamination on the transmitter window can pass through the smallest stop aperture between the scattering zone and the scattered-light detector; indeed, it often has to be allowed to pass through, because it overlaps with (i.e., it is not resolved from) the light scattered from the particle flow. Preventing the unwanted scattered light from reaching the detector may thus improve the accuracy of monitoring.
  • the optical system that prevents light scattered by the transmitter window and passing through the smallest stop aperture from reaching the scattered-light detector is arranged behind the smallest stop aperture.
  • the optical system that prevents light scattered by the transmitter window and passing through the smallest stop aperture from reaching the scattered-light detector comprises a filter that absorbs light scattered by the transmitter window.
  • the filter is sufficiently transmitting to allow for light from a compensation or calibration phase beam to reach the scattered light detector.
  • the optical system that prevents light scattered by the transmitter window and passing through the smallest stop aperture from reaching the scattered-light detector comprises a lens that focuses scattered light on the scattered light detector, a first mirror arranged behind the scattered-light detector, a second mirror with a hole arranged in front of the scattered light detector and a filter arranged between the first and second mirrors and preferably next to the second mirror, the mirrors and filter being arranged such that scattered light from the scattering zone passes directly to the scattered-light detector through the hole in the second mirror and the light scattered by the transmitter window is reflected by at least one of the mirrors and is substantially blocked by the filter.
  • the filter may be combined with one or more mirrors, to provide "black mirrors".
  • the lens' may be any suitable means for focusing the scattered light.
  • Light scattered from contamination on the transmitter window will generally be scattered from a point further from the lens than light scattered in the scattering zone.
  • the lens may be chosen such that the light scattered from the transmitter window is focused in front of the scattered-light detector. It then diverges away from and possibly past the scattered light detector and may be reflected back by the first mirror to the filter, where it is absorbed.
  • the filter is arranged between the second mirror and the detector and has a hole through which the scattered light passes on its way to the detector.
  • the monitor further comprises a light source for generating a reference beam (for example, a compensation- phase beam) and an optical system for directing the reference beam to the scattered-light detector, the first and second mirrors and the filter being arranged such that the reference beam is reflected by at least one of the mirrors, passes through the filter and reaches the detector at an intensity level sufficiently high for detection by the detector.
  • a reference beam for example, a compensation- phase beam
  • the first and second mirrors and the filter being arranged such that the reference beam is reflected by at least one of the mirrors, passes through the filter and reaches the detector at an intensity level sufficiently high for detection by the detector.
  • Such an arrangement may be preferred when the reference beam does not follow the same optical path as light scattered from the scattering zone; for example, when it is arranged to coincide with that light at one or more optical surfaces that are exposed to contamination but not elsewhere.
  • the reference beam is much stronger than the light scattered from the transmitter window, it is able to pass through the filter where the unwanted scattered light is reduced to negligible intens
  • a particle monitor for monitoring particles flowing in a stack, comprising: (i) a light source for generating a measurement beam; (ii) an optical system, for directing the measurement beam into a scattering zone in the particle flow; (iii) a scattered- light detector for detecting light scattered, from the measurement beam, by the particles as they flow in the scattering zone; (iv) a filter having a transmission function that varies radially across the filter and is selected to alter the proportion of light intensity detected at the scattered- light detector resulting from scattering from particles of a first size within a range of sizes relative to the light intensity detected at the scattered-light detector resulting from scattering from particles of a second size within the range of sizes, such that the intensity of light detected after scattering from a set of particles of the first size having a total mass M is substantially the same as the intensity of light detected after scattering from a set of particles of the second size also having a total mass M.
  • a method of monitoring particles flowing in a stack comprising: (i) generating a measurement beam from a light source; (ii) directing the measurement beam into the particle flow; (iii) passing at least some light scattered from the particle flow through a filter having a transmission function that varies radially across the filter selected to alter the proportion of light intensity detected at a scattered-light detector resulting from scattering from particles of a first size within a range of sizes relative to the light intensity detected at the scattered- light detector resulting from scattering from particles of a second size within the range of sizes, such that the intensity of light detected after scattering from a set of particles of the first size having a total mass M is substantially the same as the intensity of light detected after scattering from a set of particles of the second size also having a total mass M; (iv) detecting the scattered light that has passed through the filter.
  • Particles of different sizes in the flow will generally scatter light at different intensities at different angles. Smaller particles generally scatter light at larger angles and lower intensities, whereas larger particles generally scatter light at smaller angles and higher intensities.
  • a filter having a transmission function that varies across its surface may be used to exploit or to reduce differences in light reaching the detector from particles of different size. The exact relationship between particle size and scattering angle (and hence the exact configuration of the filter) will generally vary according to the nature of the particles and it is expected that different filters will be used in different particular applications. Such an arrangement may be used to provide a more accurate measure of properties of the particle flow by reducing or eliminating differences in detected light intensity due to different particle sizes.
  • the intensity pattern scattered from particles will usually be circularly symmetric.
  • the filter has a transmission function selected to reduce the proportion of light intensity detected at the scattered-light detector resulting from scattering from a set of particles of a third size relative to the light intensity resulting from scattering from particles of the first size.
  • a lower intensity of light may be detected from a given weight of particles of the third size than from the same weight of particles of the first size.
  • the filter is arranged to cut off light scattered from particles that are larger or, preferably, smaller than a selected particle size, for example, 10 microns.
  • the filter blocks all scattered light reaching the filter outside an annular area of the filter.
  • the filter may block all scattered light travelling to the filter from the scattering zone at an angle of less than 1 degree and all scattered light travelling to the filter from the scattering zone at an angle of more than 8 degrees, more preferably all scattered light travelling to the filter from the scattering zone at an angle of less than 2 degrees and all scattered light travelling to the filter from the scattering zone at an angle of more than 4 degrees.
  • the filter transmits scattered light reaching an annular area of the filter but blocks all other scattered light.
  • Such an arrangement may be used, for example, to give an approximate measure of the number of particles that are present in the flow in a particular range of sizes.
  • the annular area subtends at the scattering zone all angles between 1 degree and 8 degrees, more preferably between 2 degrees and 4 degrees.
  • the light intensity detected at the scattered- light detector provides an indication of the proportion of particles in the flow that are of the first size.
  • the filter may have a transmission function selected to enhance a scattered-light signature characteristic of a particular particle size (or range of sizes) .
  • the transmission function is selected such that the intensity of light detected after scattering is substantially the same for all particle sizes in the range.
  • the filter is selected to provide a detection response that is substantially uniform across the range, i.e. that does not vary with particle size.
  • a particle monitor for monitoring particles flowing in a stack, comprising: (i) a light source for generating a measurement beam; (ii) an optical system, for directing the measurement beam into a scattering zone in the particle flow; (iii) a scattered- light detector for detecting light scattered, from the measurement beam, by the particles as they flow in the scattering zone; (iv) a filter having a transmission function selected to alter the proportion of light intensity detected at the scattered-light detector resulting from scattering from particles of a first size relative to the light intensity detected at the scattered-light detector resulting from scattering from particles of a second size.
  • a method of monitoring particles flowing in a stack comprising: (i) generating a measurement beam from a light source; (ii) directing the measurement beam into the particle flow; (iii) passing at least some light scattered from the particle flow through a filter having a transmission function selected to alter the proportion of light intensity detected at a scattered- light detector resulting from scattering from particles of a first size relative to the light intensity detected at the scattered-light detector resulting from scattering from particles of a second size and (iv) detecting the scattered light that has passed through the filter.
  • a particle monitor for monitoring particles flowing in a stack comprising: (i) a light source for generating a measurement beam; (ii) an optical system for directing the measurement beam into the particle flow; and (iii) a scattered-light detector for detecting only light scattered at angles of between 1 and 8 degrees from the direction of the measurement beam when it is incident on the particle flow.
  • a method of monitoring particles flowing in a stack comprising: (i) generating a measurement beam; (ii) directing the measurement beam into the particle flow; and (iii) detecting only light scattered at angles of between 1 and 8 degrees from the direction of the measurement beam when it is incident on the particle flow.
  • Detecting only light scattered at such a small angle has the advantage of providing a long scattering volume, which smoothes out inhomogeneities due to local variations in particle properties in the flow.
  • an optical element is inserted into the measurement beam to form the reference beam.
  • the optical element is inserted into the measurement beam upstream of the transmitter window. More preferably, the optical element is a lens, still more preferably a diverging lens.
  • a laser source for providing a laser beam having low levels of peripheral light, comprising a laser, a lens and a first reflector arranged between the laser and the lens, the first reflector defining an aperture through which light emitted from the laser passes, the aperture of the first reflector being sized so as to limit the cross-section of the light passing through that aperture, and the first reflector being arranged to reflect light not passing through that aperture, the source further comprising an absorber arranged between the first reflector and the laser such that peripheral light not passing through the aperture in the first reflector is absorbed.
  • the laser source further comprises a second reflector arranged between the laser and the lens, the second reflector defining an aperture through which light emitted from the laser passes, the first reflector being arranged to reflect light not passing through the aperture in the first reflector to the second reflector and the second reflector being arranged to reflect light reflected by the first reflector back to the first reflector, the absorber being arranged between the first reflector and the laser.
  • the unwanted peripheral light is absorbed by the absorber either directly or after one or more reflections between the first reflector and the laser.
  • the lens is a convex lens. More preferably, the lens collimates the beam.
  • the absorber is adjacent to the first or second reflector. More preferably, the first or second reflector is itself the absorber, such that it is partially reflecting and partially absorbing at the output wavelength of the laser. Still more preferably, one or both reflector is, or is associated with, an absorber.
  • one or both reflectors are planar. More preferably, one or both reflectors are parallel to each other. Still more preferably, one or both reflectors are parallel to the collimating lens.
  • the first reflector is adjacent to the collimating lens. More preferably, the second reflector is adjacent to the laser.
  • the laser is a diode laser.
  • light not absorbed is specularly reflected by the reflectors and substantially none is scattered.
  • the laser source may further comprise an aperture arranged adjacent to the laser.
  • the aperture is a pin hole, more preferably of transverse dimensions between 0.5 mm and 1 mm.
  • the pin-hole is preferably placed as close to the laser diode (which has a highly divergent beam) as possible.
  • the aperture may be comprised in the second reflector. Alternatively, the aperture may be comprised in an element other than the second reflector.
  • Fig. 1 is a particle monitor according to the invention, Fig. la being a side view and Fig. lb being a plan view;
  • Fig. 2 is a plan view of an external enclosure of the monitor of Fig. 1;
  • Fig. 3 is a plan view of an internal enclosure of the monitor of Fig. 1;
  • Fig. 4a is a diagram showing ray paths in a measurement phase of operation of the monitor of Fig. 1;
  • Fig. 4b is a diagram showing ray paths in a compensation phase of operation of the monitor of Fig. 1;
  • Fig. 5 is a diagram showing ray paths in a laser source unit in the monitor of Fig. 1;
  • Fig. 6 is a plan view of an external enclosure of a preferred version of the probe of Fig. 1;
  • Fig. 7 is a plan view of an internal enclosure of the preferred version of the probe of Fig. 1;
  • Fig. 8a is a diagram showing ray paths in a calibration- mode measurement phase of operation of the preferred version of the probe of Fig. 1;
  • Fig. 8b is a diagram showing ray paths in a calibration- mode compensation phase of operation of the preferred version of the probe of Fig. 1;
  • Fig. 9 is a diagram showing ray paths in a laser source unit, which has an alternative configuration to that of Fig. 5, in the monitor of Fig. 1.
  • Probe 10 consists of four main assemblies (Fig. 1) : the external enclosure 20, which is external to the stack, the internal enclosure 30, which is inside the stack, the receiver 40 and the body 50.
  • a laser beam 60 is projected from the external enclosure 20 down the body 50 of the probe 10.
  • the laser beam 60 is reflected back through the stack gas flow 70 by optical elements in the internal enclosure 30 at the remote end of the probe 10. Scatter produced by dust carried by the stack gas flow 70 causes light to enter the receiver 40.
  • a detector 80 in the receiver 40 generates a signal sent to the main electronics in the external enclosure 20.
  • the signal generated from the dust 70 gives an indication of particle mass concentration rates in the stack.
  • a compensation phase a reference beam is used to determine the effects of contamination on exposed optical surfaces 190, 200 of the probe 10 and that information is then used in a subsequent measurement phase to compensate for those effects on the measurement signal.
  • the external enclosure 20 (Fig. 2), mounted on the end of the probe body 50, houses a laser source unit 90, all electronics (including a printed circuit board (PCB 100)), and power supplies derived from a 24-volt input (not shown) .
  • the receiver assembly 40 mounted within the probe body 50, stops just inside the enclosure 20 (Fig. 1) .
  • the enclosure 20 is a rectangular box.
  • the width of the laser optics and depth of the PCB 100 determine the length, while the side dimension is largely dictated by the area needed for the electronics PCB 100.
  • PCB 100 can have the full area of the end of the enclosure 20.
  • the main electronics PCB 100 is mounted at right angles to the longitudinal axis of probe 10. Connections to the outside world are via connectors on the main PCB 100 with cables routed through the walls of the external enclosure 20. There is also an air supply connection 110 from an external blower unit, placed on a stub 120 between the enclosure 20 and a fixing flange 130. The stub 120 allows the enclosure 20 to stand off from the stack flange 130 permitting the flange fixing bolts to be fitted and tightened in stack wall 150.
  • External enclosure 20 also comprises a solenoid 22 which rotates a rod 23, via arm 24, which in turn rotates a swinging lens assembly 150 in internal enclosure 30 (Fig. 3) .
  • the probe internal enclosure 30 (Fig. 3) contains a reflecting prism 210, transmitter air buffer 160 (Fig. 1) and transmitter window 190, together with a swinging lens assembly 150, which is used during check-phase operation of probe 10.
  • the reflector 210 is mounted directly off the probe internal enclosure 30. It is important to note that light in the periphery of the collimated output beam is undesirable, even if it is of low intensity, because such light may lead to error in measured scattered light levels (scattered light intensities are generally very low) .
  • Tube 180 carries air to the probe body 50, internal enclosure 20, external enclosure 30 and receiver enclosure 40. It also allows passage of the laser beam 60 to the internal enclosure 30 and the reflecting prism 210 in such a manner as to avoid scattering of the laser beam 60 by particles 70.
  • a second tube 185, travelling the length of the probe parallel to tube 180, from the flange 130 to the internal enclosure baffle 390 admits air to the air buffers 160, 170 in front of both transmitter and receiver windows 190, 200. Air buffers 160, 170 are designed to reduce the contamination of windows 190, 200.
  • the buffers are designed with contoured flanges so as to increase turbulence at the end of the buffers and thus reduce accumulation of contamination at the ends of the buffers.
  • the tube 185 also carries a long rod, actuated by a solenoid, to the swinging lens holder 212.
  • the laser beam 60 enters enclosure 30 via tube 180 and is reflected back in the direction from which it came (along a displaced parallel path) by reflector 210.
  • the swinging lens assembly 150 comprises concave lens 151 and a lens holder 152. The whole is pivoted so that, by rotation of rod 23, lens 151 is swung into the path of the laser beam 60 emerging from the reflector 210 before it travels to the transmitter window 190 via exit 153. The lens is swung in place during the contamination compensation phase of measurement (holder position 152') .
  • the probe receiver 40 (shown most clearly in Fig. 4b) consists of a single tube 270. Near the front of the receiver 40 is an annular iris 280 that is clear between two diameters. Iris 280 is coupled with a radially graded neutral density filter 240. (Alternatively there may be two narrower annuli of differing radii) The function of the graded filter (or annuli) is to alter the response of the monitor 10 with respect to particle size. The two most important arrangements are a response independent of particle size and a response having a cut-off at a defined particle size. Immediately behind the annular aperture 280 is a lens 220.
  • a potential disadvantage with the arrangement of probe 10 is that the transmitter window 190 and the iris 280 (which is the limiting optical stop between window 190 and detector 80) are in line of sight with each other. Hence light scattered from the edge of the iris associated with transmitter window 190 or from contamination on that window can potentially reach detector 80, as it is not spatially distinct from the light scattered from region 230.
  • the transmitter window image is reduced in magnitude by the receiver lens 220 (the window 190 being further away than the interaction volume 230, hence giving a shorter image distance) .
  • the diameter, position, and focal length of lens 220 are chosen such that all the contamination/compensation light coming through the annular iris 280 is received by the detector 80.
  • the single centrally mounted detector 80 is arranged in an aperture in a plane mirror 290 forming the end face of the receiver 40, together with the photodiode amplifier (not shown) .
  • a neutral density filter 300 (Fig. 4b) , with a central hole to allow scattered light from the interaction volume 230 to reach the detector 80 unhindered.
  • a concave mirror 310 again with a central hole, designed to reflect both light scattered from the transmitter window 190 and compensation-phase light direct from the diverged laser beam onto the detector 80, both of which will first have been reflected from mirror 290.
  • Unwanted scattered light is reduced to a negligible level by the filter 300 while direct divergent laser light present in the compensation phase provides a readily measurable signal despite two traverses of the neutral density filter 300.
  • both light scattered from interaction-volume 230 and compensation phase light are measured by the same photodiode 80 and amplifier.
  • the position of the neutral density filter 300 and concave mirror 310 are obtained from consideration of the limiting rays from both interaction volume 230 and transmitter window 190 contamination scatter.
  • a 45-degree mirror 320 (Fig. 1) , which deflects the incident laser beam to the side.
  • a second 45-degree mirror 330 deflects this beam to the rear of the receiver 40. It passes through windows into the external enclosure 20 where it impinges on a screen 340 imprinted with a graticule.
  • Fig. 5 shows laser source 90 comprises a laser diode 91 mounted on a separate small PCB 92 having the laser drive circuits on its rear.
  • the main PCB 100 is mounted in front of the laser source 90 (viewed from the outside) but fixings for the sheet are still accessible. Both sheet and PCB mount directly off the probe body 50.
  • Laser output from laser diode 91 is collimated by lens 93.
  • laser source 90 is arranged such that light in the output from diode 91 that is too far from the centre of the output beam 60 to pass through lens 93 is blocked by black mirrors 94, 95, which specularly reflect any light that is not absorbed and which exhibit very little scatter.
  • Surface 94 is mounted directly in front of diode 91 and substantially all output light passes from the diode 91 through a hole in the centre of surface 94.
  • Lens 93 is mounted in surface 95 and some of the peripheral light is absorbed in that surface.
  • Beam 60 leaves enclosure 20 along tube 180 after reflection by a 45° mirror 21.
  • the probe body 50 is built around two tubes 180, 185 running the length of the probe 10. One carries air to pressurise the internal enclosure 20, external enclosure 30 and receiver 40, and the incident laser beam 60; the other carries the air buffer air and a rod to control the compensation lens as already described. Operation of probe 10 will now be described. Normal operation of probe 10 is a measurement phase of operation (Fig. 4a) , in which the particle concentration and/or particles sizes of flow 70 are measured. The probe 10 is switched to a compensation phase (Fig. 4b) approximately every hour; operation returns to the measurement phase after the compensation check is completed.
  • laser beam 60 is admitted to the internal enclosure 30 via tube 180 from the external enclosure 20, through body 50 to the internal enclosure 30.
  • Reflecting prism 210 turns the laser beam 60 through 180 degrees and directs it back to the receiver unit 40.
  • a proportion of the beam 60 is scattered by flow 70; the residual beam is directed to graticule 340 by mirrors 320, 330.
  • the scattered light passes through an annularly graded neutral density filter 240 and iris 280 to lens 220, which focuses it onto photodiode 80.
  • the filter 240 is transparent in an annulus of inner radius 10 mm and outer radius 20 mm and opaque elsewhere. That transparent annulus transmits light scattered by particles of size 1 micron to 10 microns and substantially blocks light scattered by particles of other sizes.
  • the signal from photodiode 80 is processed to give an indication of particle concentration.
  • Windows 190, 200 are the last and first surfaces respectively through which beam 60 and light scattered from flow 70 respectively pass between internal enclosure 30 and receiver 40.
  • Windows 190, 200 are in this embodiment glass panes arranged to protect other optical elements from contamination. As they themselves are exposed to particle flow 70, windows 190, 200 are vulnerable to contamination by a build up of particles on their surfaces.
  • Air buffers 160, 170 provide some protection but contamination is still likely to occur in many stack installations.
  • the compensation phase of operation is used to determine the level of contamination. As long as contamination levels remain reasonably low, a reduction in the intensity of a reference beam can be used to calculate true scattered-light intensity values from the values actually measured during the measurement phase; thus, the effects of contamination are compensated for.
  • a concave lens 151 is swung into the beam just prior to the transmission window 190.
  • Lens 151 causes the beam to diverge so that the annular iris 280 at the entrance to the receiver section is uniformly lit. Since the exit pupil from the transmission window 190 will be virtually unchanged from that of the measurement phase, the beam traverses just those areas of both windows which are used during the measurement phase. Thus, any obstruction to either window will cause the same attenuation of the light in both measurement and compensation phases.
  • the beam 60 is substantially identical in both phases. Thus, any disturbance or drift in either the laser diode 91 or its alignment will affect both phases of operation to the same degree.
  • the same photodetector, amplification and digital train are used in both phases of operation. Any change in those will again affect both phases of operation to the same degree.
  • the sole difference between the two phases of operation is the presence of the concave lens 151 prior to the transmitter window 190 and additional fixed optic elements encountered in the receiver. Thus, any difference observed in measurements made during the contamination-check phase can be used to correct the measurement phase values.
  • the concave lens 151 is associated with a neutral density filter with continuously radially varying neutral density. Such an arrangement enables the reference beam to illuminate the receiver window in the same manner as the measurement beam.
  • Varying the laser intensity upwards from 0 per cent should give an invariant result when likewise corrected with the value at 100 per cent.
  • a check of the calibration of the probe 10 may be carried out by varying the laser intensity.
  • the calibration check or span check is preferably carried out during the compensation phase.
  • Out-of-tolerance values can be used to flag a failure of the probe 10 to span the same range.
  • a "span-check" may be carried out.
  • An alternative to varying the laser intensity is to use neutral density filters inserted into the incident beam. The value recorded in either phase of operation when the laser diode 91 is switched off will reveal any drift in the offset or "zero" values of the electronics.
  • An iris acting on the incident beam on the inner face of the transmitter window is provided if the laser source 90 fails to generate a sufficiently clean-edged beam.
  • the iris may take the form of a "black" mirror, preferably anti-reflection coated at the appropriate wavelength. Treatment of the inner surface/baffling of the tube 180 carrying the laser beam 60 reduces grazing angle reflections.
  • the signal received at detector 80 is largely independent of changes in particle flow 70 and any significant reduction in the detected signal is attributable to contamination of windows 190, 200.
  • the alignment of the laser 90 can be checked and adjusted at any time by reference to the screen 340 in the external enclosure 20, with the probe 10 still in the stack and functioning.
  • the probe design provides a means of measuring the degree of contamination affecting both transmitter window 190 and receiver window 200 in precisely those areas through which light passes in the dust measurement process. That measurement of the effects of contamination is used to compensate for the error in dust measurement caused by window fouling. Compensation is achieved by causing the transmitted beam 60 to diverge slightly as it leaves the transmitter window 190 such that the beam subsequently strikes the receiver window 200 in that area used to receive the scattered light. Measuring the signal produced in this phase of operation gives a direct measure of the transmissivity of both transmitter and receiver windows 190, 200. That value is then used to compensate the dust reading signal.
  • the probe 10 will be of different size according to the stack size.
  • the physical dimensions of the probe 10 should be modified and the optical components (i.e. focal length of lenses etc) changed, in order to produce a probe of the required dimensions.
  • the small diverging lens 151 is replaced with a compound lens 151', which is made up of a large diameter convex lens and a small diameter concave lens of greater power.
  • the auto-calibration probe has the same features as the auto-compensation probe described above with the following modifications.
  • solenoid 29 in external enclosure 20' inserts a weak diverging lens immediately in front of the laser source 90 (Fig. 6) . That causes the laser beam 60 to widen by the time it reaches the transmitter window 190.
  • That window has associated with it a compound iris (not shown) clear in the central area, a black mirror region, a further clear region and a further black mirror region.
  • the essentially two-position swinging lens assembly 150 (in or out) is replaced by a three-position optics holder 150'.
  • the optics holder 150' presents a clear area 158 (or an iris) in the measurement phase.
  • the optics holder 150' is moved so that the beam 60 passes through a diverging lens 151' as described in the auto-compensation probe above.
  • the optics holder 150' When the calibration mode is selected (lens at laser exit) , the optics holder 150' presents a converging lens 159 in measurement mode (which may have a central stop) .
  • Lens 159 causes the calibration beam to pass through the outer annulus of the transmission window 190 and focus in the interaction volume 230 of the gas stream 70 such that the rays leaving the interaction volume 230 are travelling along paths identical to those generated by scatter from dust during the measurement phase in normal mode.
  • the optics holder 150' again presents a diverging lens 151' so that the annular iris 280 at the entrance to the receiver section 40 is uniformly lit. This position in the holder 150' is the same position as used in the compensation phase in normal mode.
  • Either a single diverging lens is used, or preferably a compound lens consisting of a diverging lens with an additional central diverging lens is used.
  • a common position in the optics holder makes the use of a central stop with the laser source exit diverging lens desirable.
  • a two-position optics holder 150 may be used if a central stop is used with the laser source exit diverging lens. That would be possible by combining the optics holder 150 positions used in both measurement phases.
  • the converging lens 151' used in calibration mode measurement phase would have a central hole. Of course, there would no longer be the possibility of an iris in the normal mode measurement phase. Provision of such an iris is preferable because the normal mode measurement phase generates extremely weak signals, orders of magnitude lower than the other three selections.
  • the analysis for the calibration mode measurement and compensation phases can be made in exactly the same way as for the normal mode measurement and compensation phases, as follows. Since the exit pupil from the transmission window in compensation phase will be virtually unchanged from that in the measurement phase, the compensation phase beam is seen to traverse just those areas of both windows which are used during the measurement phase. Thus any obstruction to either window will cause the same attenuation of the light in both measurement and compensation phase.
  • the incident beam is identical in both phases; thus any disturbance of drift in either the laser or its alignment will affect both phases to the same degree.
  • the same photodetector, amplification and digital train are used in both phases; any change in these will again affect both phases to the same degree.
  • Span and offset checks may be made in exactly the same way as for the auto-compensation probe. These checks may be made in compensation phase in normal mode and in both measurement and compensation phases in calibration mode. Making the check in measurement phase in calibration mode is particularly apposite owing to the parallel with the measurement phase in normal mode.
  • the preferred embodiment of the probe thus provides a reliable calibration mechanism whilst requiring little change to the design of probe 10 previously described.
  • a means of expanding the laser beam from the normal mode, measurement phase to a significantly greater diameter in calibration mode is provided at source. That change (Fig. 6), though requiring a mechanical motion by solenoid 29, is nevertheless entirely confined to the electronics housing external to the stack, and requires no remote linkages.
  • the central area may be stopped so that in calibration mode there is less dust-induced scattered light interfering with the measurement.
  • the absorption/reflection characteristic of the stop eliminates as far as possible off-axis light escaping from the beam generator.
  • Compensation measurements made in this mode will give a measure of contamination of the receiver window 200 and the outer area of the transmitter window 190. That gives a more accurate figure with which to correct the calibration results.
  • a more complex concave mirror is provided in the receiver with an outer region of different radius to the inner area, the central hole is wider and a different position is chosen for this mirror.
  • Fig. 9 shows an alternative embodiment of the laser source, labelled 90'.
  • the angular spread of light from diode 91 that forms beam 60 is substantially less than the maximum available spread (which is desirable, for example, to form a circular beam without using a cylindrical lens) . Consequently, absorbing surfaces 94, 95 have to absorb a significant fraction of the total output power of diode 91.
  • Lens 93' is positioned further from diode 91 than lens 93 in the first embodiment (and hence lens 93' has a larger diameter) and the shape of beam 60 is determined by an iris 99 positioned just in front of lens 93'.

Landscapes

  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

L'invention concerne un appareil de contrôle de particules s'écoulant dans une pile, comprenant : (i) une source lumineuse (90) générant un faisceau de mesure (60) sur un premier côté du flux de particules (70) ; (ii) un système optique dirigeant le faisceau de mesure (60) vers un second côté du flux de particules (70) sans que le faisceau de mesure (60) soit dispersé des particules, (iii) un réflecteur (210) agencé pour réfléchir le faisceau de mesure (60) en retour vers le premier côté du flux de particules (70), (iv) un système optique dirigeant le faisceau de mesure (60) dans le flux de particules (70), de façon que la lumière émanant du faisceau de mesure (60) soit dispersée par les particules (70) ; et (v) un détecteur de dispersion de la lumière (80), destiné à détecter la lumière dispersée sur le premier côté du flux de particules (70).
EP03764014A 2002-07-15 2003-07-15 Procede et appareil de controle de particules s'ecoulant dans une pile Withdrawn EP1535049A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB0216381A GB2390893A (en) 2002-07-15 2002-07-15 Method and apparatus for monitoring particles in a stack
GB0216381 2002-07-15
PCT/GB2003/003073 WO2004008117A2 (fr) 2002-07-15 2003-07-15 Procede et appareil de controle de particules s'ecoulant dans une pile

Publications (1)

Publication Number Publication Date
EP1535049A2 true EP1535049A2 (fr) 2005-06-01

Family

ID=9940461

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03764014A Withdrawn EP1535049A2 (fr) 2002-07-15 2003-07-15 Procede et appareil de controle de particules s'ecoulant dans une pile

Country Status (4)

Country Link
EP (1) EP1535049A2 (fr)
AU (1) AU2003251334A1 (fr)
GB (1) GB2390893A (fr)
WO (1) WO2004008117A2 (fr)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2422897A (en) 2005-02-02 2006-08-09 Pcme Ltd A monitor for monitoring particles flowing in a stack
GB2436871A (en) * 2006-04-04 2007-10-10 Pcme Ltd Optical beam dump for particle monitoring system
GB2444952A (en) * 2006-12-19 2008-06-25 Pcme Ltd Improvements in methods and apparatus for monitoring particles flowing in a stack
GB2552680B (en) 2016-08-02 2018-09-19 Pcme Ltd Apparatus and method for monitoring particle flow in a stack
CN109253702B (zh) * 2018-11-08 2023-07-28 东莞职业技术学院 一种pcb钻孔快速检修方法及设备
CN112014280B (zh) * 2020-08-27 2023-11-24 苏州亿利安机电科技有限公司 直读式粉尘浓度测量仪的在线检测方法

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU873041A1 (ru) * 1978-01-24 1981-10-15 Предприятие П/Я А-7555 Фотоэлектрический преобразователь
US4249244A (en) * 1978-05-03 1981-02-03 Ppm, Inc. Electro-optical system and method and apparatus for providing automatically-compensating, traceable calibration and zeroing for light scattering devices
US4361403A (en) * 1978-06-26 1982-11-30 Loos Hendricus G Multiple wavelength instrument for measurement of particle size distributions
US4247205A (en) * 1979-02-02 1981-01-27 Measurex Corporation Gas measuring apparatus with standardization means, and method therefor
EP0108799B1 (fr) * 1982-05-10 1990-01-03 United Technologies Corporation Detecteur au laser de particules par diffusion en avant
DE3764783D1 (de) * 1986-12-08 1990-10-11 Mitsubishi Electric Corp Laserapparat.
JPS63311144A (ja) * 1987-06-13 1988-12-19 Horiba Ltd 液体中の微粒子計測装置
EP0361770A3 (fr) * 1988-09-30 1991-03-20 Kowa Company Ltd. Procédé et appareil pour mesurer des particules
US5028790A (en) * 1990-05-07 1991-07-02 Lear Siegler Measurement Controls Corporation Apparatus for full-system zero check and window soiling measurement and correction for transmissometers
US5269937A (en) * 1990-10-23 1993-12-14 Cetus Corporation HPLC light scattering detector for biopolymers
US5305073A (en) * 1992-02-12 1994-04-19 Precision Detectors, Inc. Methods and apparatus for molecular characterization
US5418615A (en) * 1994-02-25 1995-05-23 Axiom Analytical, Inc. Probe for liquid sample analysis by light transmission
US5831730A (en) * 1996-12-06 1998-11-03 United Sciences, Inc. Method for monitoring particulates using beam-steered solid-state light source
US6137108A (en) * 1998-06-17 2000-10-24 Foss Nirsystems Incorporated Instrument and method for spectroscopic analysis by reflectance and transmittance

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2004008117A3 *

Also Published As

Publication number Publication date
WO2004008117A3 (fr) 2004-03-18
AU2003251334A8 (en) 2004-02-02
WO2004008117A2 (fr) 2004-01-22
GB2390893A (en) 2004-01-21
AU2003251334A1 (en) 2004-02-02
GB0216381D0 (en) 2002-08-21

Similar Documents

Publication Publication Date Title
US5767976A (en) Laser diode gas sensor
US3994603A (en) Detection system to determine the transmissivity of a medium with respect to radiation, particularly the light transmissivity of smoke-contaminated air, for fire detection
KR0169066B1 (ko) 표면의 광열검사장치
KR20190093121A (ko) 미세먼지를 측정하기 위한 분석 장치
US5914489A (en) Continuous optical path monitoring of optical flame and radiation detectors
US5923035A (en) Infrared absorption measuring device
US20110242535A1 (en) Cell Construction For Light Scatter Detectors Having Self-Focusing Properties
US8830473B2 (en) Device for referenced measurements of reflected light and a method for calibrating such a device
RU2385461C2 (ru) Оптический времяпролетный велосиметр
US5610400A (en) Spectroscopic measuring sensor for the analysis of mediums
JP2009531658A (ja) 媒体中の粒子物体から予め画定された散乱角からの光の測定
JP2009531660A (ja) 多数のセンサ又は多数の光源経路を有する測定システムの光学的設計
EP1866629B1 (fr) Dispositif permettant de surveiller des particules coulant dans une cheminée
GB2364378A (en) Infrared optical gas measurement
JP2009515159A (ja) レーザ放射源
JP2009531657A (ja) 粒子測定システムの光学的設計
US5131741A (en) Refractive velocimeter apparatus
US3471698A (en) Infrared detection of surface contamination
WO2004008117A2 (fr) Procede et appareil de controle de particules s'ecoulant dans une pile
JPH06331543A (ja) 浮遊粒子濃度計測装置
JP2009531659A (ja) ２重機能の測定システム
US20090086191A1 (en) Optical gas detector
KR840002359B1 (ko) 적외선 필름 두께 측정기
US5404228A (en) Misalignment detection apparatus for transmissiometer with underfilled reflector
JP2009531661A (ja) 自己校正測定システム

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20050210

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR

AX Request for extension of the european patent

Extension state: AL LT LV MK

DAX Request for extension of the european patent (deleted)
RIN1 Information on inventor provided before grant (corrected)

Inventor name: THOMAS, VICTOR, FREDERICK

Inventor name: BLACKWELL, JOHN, MICHAEL

Inventor name: WAKEFIELD, MICHAEL

Inventor name: RIGBY, MICHAEL

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

RTI1 Title (correction)

Free format text: APPARATUS AND METHOD FOR MONITORING PARTICLES FLOWING IN A STACK

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20100121

RIC1 Information provided on ipc code assigned before grant

Ipc: G01N 21/53 20060101AFI20140121BHEP