Extech 461830 StroboTach Digital Stroboscope and Tachometer can freeze readings, without contact, from rotating objects so they can be analyzed. It examines motion and speed by simply targeting and synchronizing its flash rate (fpm) with a rotating object. RPMs are displayed on a 4 digit LED screen. The StroboTach provides high accuracy over a wide, dynamic range via exclusive microcomputer LSI circuits and crystal control time-bases.