Hi,
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html
What is the rotational speed of the rotor?
If the rotor has any length, what makes you sure the out of balance is going to be in phase?
Do you have a device to measure rotational position?
If so, then measure continuously one sensor and plot it against rotational position, then measure the other sensor the same way.
You can then plot the two together using the position information.
That is how wheel and spindle balancing machines do it.
Tom... 