利用飞行时间气溶胶粒子束光谱技术对大气气溶胶粒子粒谱分布进行监测是精确测量大气气溶胶粒子粒径大小及浓度的典型方法。而精确测量气溶胶粒子飞行时间是实现粒径谱精确监测的关键。利用微分法对门限电平比较法进行优化改进，利用信号微分后的零点对应信号最大值的特点，将飞行时间提取中变化的门限电平的比较转换成零电平的比较，设计了一种精确测量气溶胶粒子飞行时间的方法。该方法不但可以忽略因气溶胶粒子大小而引起的散射光强弱变化，而且，即使散射光双峰信号并非理想的对称信号，该方法也能精确地测得飞行时间。

Time-of-flight aerosol beams spectrometry is a typical method of accurate size and concentration measurement in aerosol particles' size distribution monitoring. Accurate measurement of aerosol particles' time-of-flight is the key to monitor the distribution of particles' size. A method of accurate measurement of aerosol particles' time-of-flight is designed by improving the threshold level comparison method, and the comparison of zero-level instead of the changing threshold level is realized based on differentiation since the maximum value of the original singal is corresponding to zero-level of the differential singal. By using this method, the time-of-flight can be accurately measured when the strength of the scattered light changes, or when the two peaks of the scattered light are not symmetrical.