Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/10—Investigating individual particles
  • G01N15/14—Optical investigation techniques, e.g. flow cytometry
  • G01N15/1456—Optical investigation techniques, e.g. flow cytometry without spatial resolution of the texture or inner structure of the particle, e.g. processing of pulse signals
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/10—Investigating individual particles
  • G01N15/14—Optical investigation techniques, e.g. flow cytometry
  • G01N15/1434—Optical arrangements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0205—Investigating particle size or size distribution by optical means
  • G01N2015/0238—Single particle scatter
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/10—Investigating individual particles
  • G01N15/14—Optical investigation techniques, e.g. flow cytometry
  • G01N15/1404—Handling flow, e.g. hydrodynamic focusing
  • G01N2015/1413—Hydrodynamic focussing
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/10—Investigating individual particles
  • G01N15/14—Optical investigation techniques, e.g. flow cytometry
  • G01N2015/1497—Particle shape
• • 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
  • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
  • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
  • G01N21/64—Fluorescence; Phosphorescence
  • G01N21/645—Specially adapted constructive features of fluorimeters
  • G01N2021/6463—Optics
  • G01N2021/6469—Cavity, e.g. ellipsoid

Definitions

• This invention relates to a particle monitoring system, in particular a system for monitoring temporal changes in the size and population spectra of particles in a given fluidic environment.
• 'particles 1 is intended to apply to both solid bodies and drops of liquid.
• Particle analysers are known for example, as described in UK Patent Application No 2022816A in which the size and, to a certain extent, shape of the ambient particles can be determined.
• a present monitoring system is described in UK Application No GB 2132767A which employs a number of monitoring devices set at separate locations and a receiving means to respond to signals from the monitoring devices.
• the system is more specific to the measuring of water content and has the disadvantage of not giving any information as to temporal changes in the moisture content of the medium in which the monitoring devices are placed, but merely gives readings taken by the separate monitors over very short periods of time.
• a further disadvantage of this system is that the monitors themselves cannot store information and so have to be connected up separately to the central receiving unit where the information is stored.
• a particle monitoring system includes a plurality of independent particle monitors spatially separated and under the control of a master computer, wherein each particle monitor employs laser light scattering techniques for detecting and analysing individual particles in its vicinity, and stores the results over a given time period, the stores results being readable by the master computer for processing functions.
• the processing functions may include the representation of the stored results as a function of time and/or location in graphical form.
• i dividual monitors may take any suitable form but preferably each comprises a irst scatter chamber including a • first concave reflector, a sample of fluid in the form of a laminar flow intercepting at right angles a beam of radiation at the focal point of the first concave reflector, and a second chamber leading from an aperture in the first chamber. Light scattered by the individual particles in the sample is directed towards radiation collectors, converted into electrical signals, and analysed.
• Such monitors are further disclosed in co-pending Applications (applicants references P0543 0D claiming priority from UK patent application No. 8726304 -and P0544W0D claiming priority from UK patent application No. 8726305) by the same inventors.
• the system may have a present alarm capability, so that when the system detects given conditions, an audible or visual alarm is triggered.
• Fig 1 is a schematic diagram of the deployment of several Particle Monitors in communication with a Central Master Computer.
• Fig 2 is a schematic diagram of a single Monitor.
• Fig 3 is a schematic diagram of the electronic processing system.
• a number of independent monitors 1 are operated under the control of a central master microcomputer 2. If only tv/o monitors are deployed the master microcomputer is not absolutely necessary for possible processing of recorded data to reveal behavioural trends.
• the master microcomputer is typically a commercial microcomputer, such as IBM-PC or an Olivetti M24, with custom interface electronics. Unlike the monitors (which would be battery powered), the master microcomputer 2 requires mains power.
• each monitor functions under its own real-time calendar clock. The clocks are used to control the acquisition of data and can be used to initiate a synchronised start between several remote monitors, the start-time having been programmed into the monitor some time earlier.
• a synchronised start can be generated by radio-control or by fibre-optic link 3 from the master computer.
• each monitor 1 draws in ambient air by means of an electric pump, detects and measures each individual particle in the air at high throughput rates by means of laser light scattering, and records the results of each measurement in non-volatile memory.
• Each monitor 1 communicates with the central computer 2 via radio or optical fibre links 3 or by means of a removeable memory module.
• an electrically driven pump 4 draws in sample air 5 from the environment together with sheath air 6 through the filter unit 7.
• the sheath air 6 confines the sample air-stream 5 by means of lamina focussing so that it passes accurately through the scattering volume at the focus of the reflector 8.
• a laser diode 9 typically a Philips type 513 CQL
• a laser diode 9 operating at a wavelength of 850nm and a continuous wave power of 20mW produces an output beam 10 which is focussed so as to intercept orthogonally the same air-stream 5 at the scattering volume.
• the cross-section of the beam 10 at the inter ⁇ section point is approximately 30 ⁇ m deep by 4mm across. Particles carried in the sample air-stream 5 generate scattered light pulses as they pass through the laser beam 10 and the reflectors 8 converge this scattered light to light detector points. At these points are placed miniature photomultiplier tube detectors 11 (typically
• SUBSTITUTE SHEET circuits 14 which output binary values corresponding to the maximum value of the pulses. These binary values are then used as addresses to a look-up table which translates the pulse magnitudes to equivalent particle sizes.
• Each of the (probably 20) size intervals is repre- sented by a 24-bit counter (ie, 0 to 16 million) and the final output histograms, stored in the memory module, show the values of all counters at the end of each integration period.
• the memory module 15 comprises pages of random-access-memory (RAM), each of 32K bytes, and numbering up to a possible 256 pages. It is anticipated that no more than 16 pages (or 0.5 MBYTES) of RAM will be necessary.
• RAM random-access-memory
• Each monitor is equipped with a simple key-pad and display, so that operational parameters can be entered and results can be observed in the field.
• the memory module 15 of each monitor 1 is preferably removable so that the data can be returned to the master microcomputer
• Spare memory modules can be plugged into the monitor to continue data collection if required.
• each histogram representing the particle size spectrum (ie, number of particles versus size) recorded over a precise time interval or integration period.
• a time-code Associated with each histogram is a time-code and an identity-code for later post ⁇ processing use.
• This integration period is user-definable, and can vary from, say, 100ms (allowing 10 histograms to be recorded per second), to several minutes.
• the data storage capacity of the monitor would normally be sufficiently large for data to be continuously recorded for a period from minutes up to several hours, the only limit being that of the built-in memory capacity, and the battery capacity.
• the monitors are designed to detect individual particles in the range of 1 to 15 ⁇ m equivalent diameter at maximum rates in excess of 30,000 per second, and to size the particles into a number of size windows, typically of l ⁇ m intervals. Additionally there may be over- range and under-range windows. They collect data over user definable integration period which may be varied from 100ms to 5 minutes, and store the results in non-volatile memory together with elapsed time and identity codes. They can repeat the previous step continuously
• SUBSTITUTE SHEET over a defined run-time which may be varied from 1-10,000 integration periods.
• the detection run-time of the monitors may be initiated by means of a front-panel switch, a real-time operated delay switch, or, as an optional extra, by remote control using radio or fibre-optic link.
• the monitors may display on request, using a built-in LCD display, numerical graphical representations of the temporal changes in size spectra recorded over the run-time or any part of the run-time.
• the monitors are designed to accept user definable alarm conditions and generate an audible (or visual) alarm when these conditions are met. Such conditions may be, for example, a rapid increase in particle count in one or more specified size windows, a particle count which exceeds a pre-specified value, etc.
• the monitor memory could store the size spectrum of a specific aerosol and generate an alarm when the incoming ambient air produces a similar spectrum to within predetermined thresholds, Such conditions would be implemented in software and thus may be modified to suit experimental requirements.
• the monitors are also designed to display their current opera ⁇ tional status, including overall count rates, battery status, elapsed run-time, specified integration period, alarm conditions in operation etc (to users requirements).
• the system allows the transfer of recorded numerical data in the memory module 15 to an external printer and aiso allows it to be removed and interrogated using the remote master microcomputer system.
• microcomputer system and the post-processing functions it performs could vary for specific experimental conditions, but the functions performed would generally include the following:- The plotting of graphical data representing the change in recorded size spectra from a single monitor as a function of elapsed run-time; the plotting of graphical data representing the change in particle population density in one specific size interval as a function of elapsed run-time; and if data was recorded simultaneously from several monitors placed at specific locations, then graphical data could be plotted representing the change in particle spectra not only as a function of elapsed run-time but also as a function of geographical location.

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• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Physics & Mathematics (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth 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)

Applications Claiming Priority (8)

Publications (1)

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• 1988
  • 1988-11-10 AU AU26204/88A patent/AU2620488A/en not_active Abandoned
  • 1988-11-10 EP EP88310597A patent/EP0316173A1/de not_active Withdrawn
  • 1988-11-10 EP EP88909571A patent/EP0386061A1/de active Pending
  • 1988-11-10 WO PCT/GB1988/000972 patent/WO1989004470A1/en not_active Application Discontinuation
• 1990
  • 1990-04-06 GB GB9007801A patent/GB2231403A/en not_active Withdrawn

Non-Patent Citations (1)

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