IF THE SPEED IS MORE THAN UPPER LIMIT, YOU MAY STILL DETERMINE THE SPEED BY FIRST MAKING MEASUREMENTS WITH A LOWER FLICKER FREQUENCY AND THEN MAKING A SIMPLE CALCULATION (AS EXPLAINED IN THE APPENDIX).
It can also be used for measuring medium rotation speeds (up to 2,700 RPM), but at such speeds there is a risk of spontaneous tearing away of the magnet and strong vibration due to center-of-gravity shift.
Changing the frequency of the flicker of light may help detect the rotation speed.
When the flicker frequency of light coincides with the speed of any object, such as a fan, the rotating fan may appear to be stationary.
The magnetic tachometer is best suited for measuring low rotation speeds (from 6 revolutions per minute).