The 461891 is a digital contact tachometer designed for direct measurement of rotational speed and linear surface velocity in industrial and maintenance applications. It features a large 5-digit LCD display with autoranging capability, delivering measurements from 0.5 to 19,999 rpm with ±(0.05% reading + 1 digit) accuracy, and can also measure linear surface speeds in feet per minute (0.2 to 6560 ft/min) or meters per minute (0.05 to 1999.9 m/min) using interchangeable accessory wheels. The instrument includes a 1-second sampling time for speeds above 6 rpm, built-in memory for MAX/MIN value recall, and comes equipped with cone tip, flat tip, and spare wheel attachments. Typical applications include motor speed verification, conveyor belt monitoring, spindle speed checking, and maintenance diagnostics where quick, non-contact or light-contact measurements are required.