Sedimentation particle size analyzer combines particle differential sedimentation with photometric detection. Particle sizes can be measured over a wide range because sample particles are settled in any of three modes: The Gravitational sedimentation mode, the Centrifugal sedimentation mode, the Multi mode (Combining gravitational sedimentation and centrifugal sedimentation). Operation in any mode is quite easy through a dialogue. All of the data is calculated by the built-in microcomputer. Various types of data are available, including cumulative distribution graphs, differential distribution graphs, median diameter, and modal diameter. The instruments are designed and engineered to deliver high accuracy and high precision. This is ensured by the use of a sample cell that has a stabilizing plate which prevents the irregular movement of particles, an inverter that controls the centrifuge unit, programming which compensates for the effect of particle diffusion and concentration, and programming that corrects for the extinction coefficient. Various safety devices and self-diagnostic functions are also incorporated.