Extech 461830-NIST - NIST Calibration Certificate - Digital Strobo Tachometer features: Freeze motion and analyze rotating objects without contact; Checks and analyzes motion and speed by simply aiming and synchronizing its flash rate (fpm) with a rotating object; rpms on 4 digit LED display; High accuracy over a wide, dynamic range via exclusive microcomputer LSI circuit and crystal control time-base, etc.