The tachometer is one of the instruments commonly used in the machinery industry to determine the speed and linear speed of the motor. It can accurately measure the speed of impeller blade, drum and rotating shaft, and is widely used in motor, fan, washing machine, textile, automobile, aircraft, ship and other industries. Function description: Test range: 2.5RPM ~ 99,999RPM(RPM) Resolution: 0.1RPM (2.5 ~ 999.9RPM) 1RPM (1000RPM or more) Measurement accuracy: ± (0.05% +1 word) Sampling time: 0.8 seconds (above 60 RPM) Effective measuring distance: 50mm ~ 500mm (laser light source) Time base: 6MHz quartz crystal oscillator Memory function Range selection: Automatic switching Power source: Single 6F22 9V battery (not included) Power consumption: about 35mA