Disdrometer
From Glossary of Meteorology
disdrometer
An instrument that measures and records the sizes of raindrops.
A common type of disdrometer consists of a sensitive transponder that measures the momentum of individual drops as they fall onto an exposed horizontal surface. Size is determined from momentum through calibration, and the drop-size distribution is obtained by keeping a tally of the number of drops in different size categories that fall onto the surface in a given period of time.
