900 - 1000 RPM sensor

I would like to start a little project with arduino. This projec aim to accounting about 900 or 1000 rpm What kind of sensor I must use .... What is your opinion ?

http://hizliresim.com/ZMdX0Z

It all rather depends on how big the thing doing 15 to 17 Hz is, doesn't it?

You need to do a better job of defining the requirements - what is the environment? Is this out in the weather or on an engine of some sort? Does it have to be waterproof? What power are you using? What access do you have to whatever is rotating? What are you doing with the data? Display, log or ?