Bora

Different types of RPM counter meters are available in the market and are quite inexpensive, buy one.

Thanks

The most reliable inexpensive method is if you have something protruding from a shaft that can be sensed by an inductive proximity sensor as it passes by, then fed into a counter / rate meter. That could be a shaft key, gear teeth, a cam lobe anything metal that is at a different diameter from the axis of rotation than the main shaft.

Next would be an optical sensor looking for a specific mark on the shaft, but these are subject to dirt causing misreads.

Less reliable but simpler if you only want to measure once is a hand held rubber wheel tachometer.

Thanks,,, all of them seems quite practical,, will try the optical one.