The tachometer has three functions:

* optical measurement of rotational speed. Paste a piece of reflecting foil on the shaft, then measure from a distance of up to 60 cm (2 feet).
* contact measurement of rpm. Fit on a contact cone and hold it against the end of the shaft.
* contact measurement of peripheral speed. Fit on a contact professional wheel and hold it against the moving surface.

Measuring range 50 to 19999 rpm, 5 to 1999 m/minute.