Hello Old School.
One suggestion for a simple rig might be to drive a permanent magnet DC motor and measure the voltage that is produced.
I take it the actual numbers of rpm are not in themselves important, you are more likely to be interested in orders rather than precise numbers and with imagination you could establish some calibration points to draw a graph for the system.
A fancy non contact method would be to use a strobe light shining on a segmented disc for 'stopped motion' calibrations if the graph is not sufficiently linear; it might even be possible to hire something for that stage.
Smiths Instruments made rev counters in the past, hand held devices that had different operating ranges which went up to the speeds you are expecting, but finding one of those today is a bit of a lottery.
Regards
Brian
Edited By Brian Wood on 03/09/2016 10:40:03