Patent ID: 6401553
Filing Date: 2002-06-11
Classification: G01N

Abstract:
A method for measuring particle size distribution with an electrical impactor, comprising the steps of:directing a flow transporting particles through an inlet to a chamber having side walls which comprise a stage, which is electrically connected to a current measurement unit, and an insulator which electrically insulates the stage from at least one of a frame section and from other stages; directing in the chamber the flow through holes of a nozzle part which is essentially perpendicular to the flow and electrically connected to the stage; deviating sharply the flow direction of the flow which has passed through the holes of the nozzle part by placing a collector surface, solid at the locations of the holes of the nozzle part, near the nozzle part after the nozzle part in the direction of the flow; measuring an electrical current with the help of a current measurement unit which is electrically connected to the collector surface, said current being produced when out of the particles transported in the flow, particles which are larger than a desired size become detached from the flow as the flow direction changes sharply and impinge on the collector surface, thus transferring their charge to the collector surface; and direction the flow out of the chamber through at least one outlet, situated on the collector surface, wherein an electric field formed by charge accumulated on the insulator to the chamber on the route of the flow is minimized to minimize Coulombic losses of the charged particles.