Optical Airborne Particle Counter Operation
For most cleanroom airborne particle measurements, an optical single particle counter (OPC) is used. An OPC measures particle size in response to the amount of light level change caused by the presence of a particle as it passes through a sensing zone within the OPC. The light level change can be positive or negative, depending upon the nature of the OPC. Three types of measurements are made with OPCs. Particles suspended in gas or liquid or on surfaces are measured. Particles can be counted and sized in ambient air or in either compressed or low-pressure gases with these devices. Particles can be measured in a variety of liquids, including those that are extremely corrosive. Particles can also be measured on surfaces that are actual product surfaces or surrogates of the product or of the cleanroom environment. The last procedure is used to indicate deposition upon critical surfaces that cannot be removed from the product area for testing purposes.
KeywordsParticle Counter Sheath Flow Sensitive Zone Illumination Wavelength Illumination Beam
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