Abstract：Taking the concentration of NaCl electrolyte, gain and current as experimental factors and the noise level as an experimental indicator, an orthogonal experiment was designed. By employing the mathematical statistical software SPSS17.0, the range analysis and variance analysis were conducted on the experiment and tendency charts about factors and indicators were drawn. The results show that the current and gain have significantly effect on noise level, and the effect of the NaCl concentration on noise level is not significant. The order of factors according to their significance from great to small is current, gain, NaCl concentration.According to the range analysis and tendency chart, the optimum conditions to control noise level of Coulter Multisizer 3 particle size meter are as follows. The concentration of electrolyte NaCl is 4%, the gain is set to 32, the current is set to-800 μA. Based on the optimal conditions, the noise level can be reduced to 0.404 μm.

Keywords: particle size meter; noise level; orthogonal design; SPSS software