Patent ID: 7471076

Claim:
An apparatus for measuring a number of particles comprising: a particle charging means for charging particles to a monopolarity; an inner guide duct into which clean air is introduced; an electrode to which a high voltage is applied, the electrode being installed in the inner guide duct in a lengthwise direction of the inner guide duct; a power supplying means for supplying power to the electrode; an outer guide duct positioned outside the inner guide duct and being longer than the inner guide duct, the particles charged by the particle charging means being introduced between the inner guide duct and the outer guide duct; a particle separating means having an upper end positioned at an inner lower side of the outer guide duct and including a plurality of particle separating ducts that are spaced apart from a lower end of the electrode, wherein an empty space is formed between the lower end of the electrode and an upper end of the particle separating ducts and the particle separating means separates the charged particles according to size when the charged particles flow down in the empty space; and a particle counting means connected to the particle separating means for counting the particles separated according to size by the particle separating means.