A grain-size analyzer with settling tube system was established．A personal computer controls this system and process data．
We measured the grain-size distribution of same samples by three kinds of measuring method； the sieving method，sedimentation method with Emery tube，and sedimentation method with this analyzer．Samples are standard glass spheres（0.177-0.250mm）and beach sand．Analyzing grain size distribution is the moment method．No significant difference among three measuring methods recognized on standard glass spheres．However，the arithmetric mean of beach sand given by this analyzer is approximately 0.4 phi，which is finer than that by the other methods．On sieving method，platy particle may readily pass diagonally through mesh．The other hand，concentrated sample may accelerate settling velocity in Emery tube．Thus size determination by these two methods is coarser．The analyzer in the present study is less susceptible to these factors．Further，this analyzer has high possibilities to connect with the hydrometer technique，and its measurement time is short in comparison with the other methods．