A bipolar charge measurement system for aerosol characterization

This paper reports the development of a bipolar charge measurement system for aerosol characterisation. The system incorporates a front-end cylindrical arrangement consisting of two "D" shaped precipitation sections. Each of these sections incorporate wire electrodes maintained at a high potential of opposite polarity. The interface between the two "D" sections is a thin wedge, the front-end of which acts as a bifurcation for the incoming aerosol. The test aerosol is drawn through the bifurcation separator using a suction pump, and subject to an appropriate electric field. Depending on the electric field distribution and air flow characteristics, a particle of opposite polarity to that of the potential applied to the wire electrodes will exit the separator. This separation section is connected to a series of five "D" shaped Faraday chambers to collect the unipolary charged aerosol of different charge to mass ratio. Both analytical and numerical calculations were performed to optimize the design of the manufactured system. Preliminary tests were carried out with an aerosol of known size and charge distribution. The results obtained are in good agreement with the theoretical predictions.