TACHOMETER The Extech PocketTach Mini Photo Tachometer is ergonomically designed and pocket sized to measure rpm and surface speed up to 99,999 rpm. The meter is easy to operate by simply contacting the rotating object with the sensor tip and read the data. Model 461700 is a non-contact instrument that features an integral light beam with an ideal measurement range of 6 inches distance. Model 461750 is a contact instrument with surface wheels that enable the tachometer to measure linear surface speeds in ft/min, m/min, and yd/min. Specifications:  Display counts: 99,999 count LCD rpm range: 10 to 99,999rpm Basic accuracy: ±(0.1%rdg + 2d) Sampling time: 1sec>60rpm, >1sec>10 to 60rpm Maximum rpm resolution: 0.001 Dimensions: 4.88 x 1.97 x 1.3" (124 x 50 x 33mm) Weight: 4oz (114g)