An Electrical Detector for Nanometer-Sized Aerosol Particles Detection: Development of the Equipment and Preliminary Results
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An electrical detection system for measuring number concentration of nanometer-sized aerosol particles in the size range between 1 nm – 1 µm using electrostatic charge measurement technique was developed in this study. It consists of a size selective inlet, a particle charging system, an ion trap, a Faraday cup electrometer, a signal conditioning and processing system, and an I/O control and human-computer interface. In this system, an aerosol sample first passes through the size selective inlet to remove particles outside the measurement size range based on their aerodynamic diameter, and then pass through the unipolar corona charger that sets a charge on the particles and enter the ion trap to remove the free ions. After the ion trap, the charged particles then enter the Faraday cup electrometer for measuring ultra low current about 10-12 A induced by charged particles collected on the filter in Faraday cup corresponding to the number concentration of particles. Signal current is then recorded and processed by a data acquisition system. The performance of the prototype electrometer circuit used in this work was evaluated and compared with a commercial electrometer and good agreement was found from the comparison. Finally, the preliminary experimental testing results were also shown and discussed.
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