The United States of America As Represented by the Administrator of the

Harvard College

Msp Corporation

Harvard Corporation

Robert M Burton

Petros Koutrakis

Costas Sioutas

Virgil Alan Marple

Steven M Behm

A virtual impactor that can remove essentially all of the particles from an airstream is disclosed. Disclosed are a method of separating particles from the airstream using this virtual impactor, a method of concentrating the particulate matter in an airstream, and the concentrated airstream.

Virtual impactor process for removing particles from an air stream

A virtual impactor that can remove essentially all of the particles from an airstream is disclosed. Also disclosed are a method of separating particles from the airstream using this virtual impactor, a method of concentrating the particulate matter in an airstream, and the concentrated airstream.

Virtual impactor for removing particles from an airstream and method for

A volumetric flow controller is used in connection with a virtual impactor classifier to control two separate flows in separate lines from an air pump. Each line has a flow control valve controlled in response to flow signals that are obtained from a pressure transducer that provides an electrical signal proportional to pressure. Pressure changes are sensed and the provided electrical signal is compared with a reference and will actuate a damper motor and move a flow control butterfly valve in the flow line for adjusting the flow when the pressure signal is different from the reference. The circuitry used provides for a dead band, so that changes in the butterfly valve setting will not occur unless the flow varies a selected amount, and also a timer control is used so that the motor operating the damper will be operated only at selected time intervals to prevent 'hunting' or continuous operation of the valves. Further, temperature compensation signals can be provided as desired. The ability to control the flow volume provides for more accurate aerosol sampling and cut off points for the size of particles being sampled.

Volumetric flow controller for aerosol classifier

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Raleigh, NC, United States of America

Robert M Burton