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A Novel Technology for the Measurement of Nanoparticle Number Concentration
by Hiroshi Okuda1
(Received July 3, 2018）
We have developed a new technology to measure the nanoparticle number concentration in the air, where there are concerns about health effects. This is a kind of diffusion charge method that charges the particles, uses electrostatic force to attract them to the measuring electrode, and then obtains the particle concentration by measuring their charge. In conventional diffusion charge methods, the sensitivity has a large dependency on particle size because particles with larger particle diameters tend to become multiply charged. By making the sample gas flow and the electric field for capturing the sample gas at the measurement electrodes orthogonal, and by combining a new classifier/detector, where multiple measuring electrodes are arranged in the direction of the sample gas flow, with a new charge adjustment device that can control the particle charge amount by controlling the corona discharge current, it was possible to greatly reduce particle size sensitivity dependence compared with the conventional diffusion charge type. It was also confirmed that the linearity and reproducibility of the sensitivity is sufficient for automobile exhaust gas measurement and atmospheric environmental measurement and that it maintains good performance even at a pressure equivalent to an altitude of 5000 m.
Keywords: Nano aerosol, Electrical mobility, Diffusion charge
1Research & Development Department, Analytical & Measuring Instruments Division, Shimadzu Corporation, Kyoto, Japan
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