On Friday, August 30, 2013 10:00:54 AM UTC+1, AnthonyL wrote:
I'd like to know/measure the speed (rpm) of a small electric 3 blade

fan. Any easy ideas?



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AnthonyL

Have you got a multimeter that measures AC frequency ?
If so, you might be able to cobble together something with a battery, photocell and a light source.
Or you could rig it so it just clips a piece of card or something and compare by ear the pitch with comparison tones from the internet.
Simon.