Runs on 12 volts DC.
Simply place a piece of photoreflective material on your spinning part 3 centimeters from the sensor, and the infrared beam will bounce off of it and back to the sensor.
This is how it measures the rpm of a rotating object with no contact.
There is an output of 4.4 volts as well, for either high or low revolutions.

- Display dimension : 3.43x1.59 inch.
- PCB dimension : 3.43x3.22 inch.
- Recommended Housing : FB05
- Power supply : 12 VDC.
- Can measure rpm. in a 100-60,000 revolutions/minute range.
- 5 digit LED display.
- Distance between the photo reflective infra-red sensor and reflector = 3 cm.