Features of Contact Tachometer Lutron DT-2235B : This contact tachometer features a bright 5-digit display with a 10 mm LCD for clear visibility. It operates using four AA 1.5V batteries, ensuring consistent and reliable performance. This device offers a wide speed range from 5 to 19,999 RPM for accurate rotational measurements. It can also measure surface speed from 0.05 to 1,999.9 meters per minute, providing precise results across various applications.