Importance

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Abstract

Disclosed is a particle sensor of the type having (a) a light beam, (b) an air tube flowing a stream of air across the light beam at a volumetric flow rate, and (c) an air pump providing the stream of air through the tube, across the light beam and along an air flow path. In the improvement, the particle sensor includes a flow-controlling apparatus in series with the flow path for slightly trimming or adjusting the flow rate, i.e., the rate usually set at the factory before shipping. Such flow-controlling apparatus is selected from a group of apparatus including a choke valve (preferably an adjustable choke valve), a slip clutch, a speed-adjustable blower drive motor and a plurality of conduits. The conduits may have the same passage cross-sectional area and differing lengths, the same length and differing cross-sectional area or a combination of such conduits. A new method for assaying an airborne particle is also disclosed.

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First Claim