Detection methods There are several methods used for detecting and measuring particle size or size distribution — light blocking (obscuration), light scattering, Coulter principle and direct imaging.   The light scattering method is capable of detecting smaller-sized particles. This technique is based upon the amount of light that is deflected by a particle passing through the detection area of the particle counter. This deflection is called light scattering. Typical detection sensitivity of the light scattering method is 0.05 micrometre or larger. However, employment of the condensation nuclei counter (CNC) technique would allow a higher detection sensitivity in particle sizes down to nanometre range. A typical application is monitoring of ultrapure water in semiconductor fabrication facilities. The light blocking method is specified for particle counters that are used for counting in hydraulic and lubricating fluids. Particle counters are used here to measure contamination of hydraulic oil, and therefore allow the user to maintain their hydraulic system, reduce breakdowns, schedule maintenance during no or slow work periods, monitor filter performance, etc. Particle counters used for this purpose typically use ISO Standard 4406:1999 as their reporting standard, and ISO 11171 as the calibration standard. Others also in use are NAS 1638 and its successor SAE AS4059D. Direct imaging is a technique that uses the light emitted by a laser as a source to illuminate a cell where particles are passing through. The technique does not measure the light blocked by the particles, but rather measures the area of the particles functioning like an automated microscope. A pulsed laser diode freezes the particle motion. The light transmitted through the fluid is imaged onto an electronic camera with macro focusing optics. The particles in the sample will block the light, and the resulting silhouettes will be imaged onto the digital camera chip. Optical counting 300px|Diagram of a particle counter 300px|Diagram of a vision-based particle counter%DIFDELCMD < %DIFDELCMD < %%% The nature of particle counting is based upon either light scattering, light obscuration, or direct imaging. A high intensity light source is used to illuminate the particle as it passes through the detection chamber. The particle passes through the light source (typically a laser or halogen light) and if light scattering is used, then the redirected light is detected by a photo detector. If direct imaging is used, a halogen light illuminates particles from the back within a cell while a high definition, high magnification camera records passing particles. Recorded video is then analyzed by computer software to measure particle attributes. If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and tabulated into standardized counting bins. The image to the right shows a light scattering particle counter diagram. More information about types of particle counters and types of particle detection follow in this article. Direct imaging particle counting employs the use of a high resolution camera and a light to detect particles. Vision based particle sizing units obtain two dimensional images that are analyzed by computer software to obtain particle size measurement in both the laboratory and online. Along with particle size, color and shape analysis can also be determined.  Other types Remote particle counters Small particle counters that are used to monitor a fixed location typically inside a cleanroom or mini-environment to continuously monitor particle levels. These smaller counters typically do not have a local display and are connected to a network of other particle counters and other types of sensors to monitoring the overall cleanroom performance. This network of sensors is typically connected to a facility monitoring system (FMS), data acquisition system or programmable logic controller. General Environments Air particle monitoring is required for ensuring the manufacturing environment is free from contamination level that will cause defects. It is performed either for the entire cleanroom areas (ballrooms, bays and chases), or specific local controlled environments (tools and minienvironments).
Detection methods 300px|Diagram of a particle counter 300px|Diagram of a vision-based particle counterThere are several methods used for detecting and measuring particle size or size distribution — light blocking (obscuration), light scattering, Coulter principle and direct imaging. A high intensity light source is used to illuminate the particle as it passes through the detection chamber. If light scattering is used, then the redirected light is detected by a photo detector. The light scattering method is capable of detecting smaller-sized particles. This technique is based upon the amount of light that is deflected by a particle passing through the detection area of the particle counter. This deflection is called light scattering. Typical detection sensitivity of the light scattering method is 0.05 micrometre or larger. However, employment of the condensation nuclei counter (CNC) technique would allow a higher detection sensitivity in particle sizes down to nanometre range. A typical application is monitoring of ultrapure water in semiconductor fabrication facilities. If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and tabulated into standardized counting bins. The light blocking method is specified for particle counters that are used for counting in hydraulic and lubricating fluids. Particle counters are used here to measure contamination of hydraulic oil, and therefore allow the user to maintain their hydraulic system, reduce breakdowns, schedule maintenance during no or slow work periods, monitor filter performance, etc. Particle counters used for this purpose typically use ISO Standard 4406:1999 as their reporting standard, and ISO 11171 as the calibration standard. Others also in use are NAS 1638 and its successor SAE AS4059D. %DIFDELCMD < %DIFDELCMD < %%% If direct imaging is used, a halogen light illuminates particles from the back within a cell while a high definition, high magnification camera records passing particles. Recorded video is then analyzed by computer software to measure particle attributes. Direct imaging particle counting employs the use of a high resolution camera and a light to detect particles. Vision based particle sizing units obtain two dimensional images that are analyzed by computer software to obtain particle size measurement in both the laboratory and online. Along with particle size, color and shape analysis can also be determined. Direct imaging is a technique that uses the light emitted by a laser as a source to illuminate a cell where particles are passing through. The technique does not measure the light blocked by the particles, but rather measures the area of the particles functioning like an automated microscope. A pulsed laser diode freezes the particle motion. The light transmitted through the fluid is imaged onto an electronic camera with macro focusing optics. The particles in the sample will block the light, and the resulting silhouettes will be imaged onto the digital camera chip. Specialized types Remote particle counters Small particle counters that are used to monitor a fixed location typically inside a cleanroom or mini-environment to continuously monitor particle levels. These smaller counters typically do not have a local display and are connected to a network of other particle counters and other types of sensors to monitoring the overall cleanroom performance. This network of sensors is typically connected to a facility monitoring system (FMS), data acquisition system or programmable logic controller. General environments Air particle monitoring is required for ensuring the manufacturing environment is free from contamination level that will cause defects. It is performed either for the entire cleanroom areas (ballrooms, bays and chases), or specific local controlled environments (tools and minienvironments).
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300px|Diagram of a particle counter 300px|Diagram of a vision-based particle counterThere
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A high intensity light source is used to illuminate the particle as it passes through the detection chamber.
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If light scattering is used, then the redirected light is detected by a photo detector.
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If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and tabulated into standardized counting bins. The light
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Direct imaging is a technique that uses the light emitted by a laser as a source to illuminate a cell where particles are passing through. The technique does not measure the light blocked by the particles, but rather measures the area of the particles functioning like an automated microscope. A pulsed laser diode freezes the particle motion. The light transmitted through the fluid is imaged onto an electronic camera with macro focusing optics. The particles in the sample will block the light, and the resulting silhouettes will be imaged onto the digital camera chip.
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Optical counting 300px|Diagram of a particle counter 300px|Diagram of a vision-based particle counter
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The nature of particle counting is based upon either light scattering, light obscuration, or direct imaging. A high intensity light source is used to illuminate the particle as it passes through the detection chamber. The particle passes through the light source (typically a laser or halogen light) and if light scattering is used, then the redirected light is detected by a photo detector.
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If light blocking (obscuration) is used the loss of light is detected. The amplitude of the light scattered or light blocked is measured and the particle is counted and tabulated into standardized counting bins. The image to the right shows a light scattering particle counter diagram. More information about types of particle counters and types of particle detection follow in this article.
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Direct imaging is a technique that uses the light emitted by a laser as a source to illuminate a cell where particles are passing through. The technique does not measure the light blocked by the particles, but rather measures the area of the particles functioning like an automated microscope. A pulsed laser diode freezes the particle motion. The light transmitted through the fluid is imaged onto an electronic camera with macro focusing optics. The particles in the sample will block the light, and the resulting silhouettes will be imaged onto the digital camera chip.
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