Extech 461891 High Precision Contact TachometerExtech 461891 Contact Tachometer Contact Tachometer For Contact rpm measurements Plus Linear surface speed measurements in ft min or m min Key Features: Large 5 digit LCD display is easy to read Built in memory recalls last MAX MIN value stored Autoranging with 0. 05% accuracy Contact measurements from 0. 5 to 19,999rpm plus linear surface speed measures in ft min or m min Simply contact rotating object with sensor tip and read Accessory wheels enable