Converting 3-Axis MEMS Accelerometer Data to Motor RPM for Speed Comparison

I installed a MEMS sensor on a motor that I can control the motor speed. I'm recording the information from the sensor (x, y, z)I'm trying to compare if the MEMS sensor reading is ad the same as my motor speed. But I don't know how to convert the data from the 3 Axis MEMSFor example I set my motor speed to 28.84 RPM, I have the data from the MEMS sensor (as a X,Y,Z array)How i can convert the data to RPM or vice versa to be able to compare the reading to the actual motor speed .thanks

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Hi Mike
Thank you for your replay.

What I'm trying to do is to measure the delta between the motor and the accelerometer  measurement.I assume that my motor is very accurate so if ill set the motor to rotate in a defined speed  he will to it.I have a list of different speed in RPM (from 20 to 500) each time I set the motor to rotate in a specific speed, then I'm recording the accelometer data (acc_x, acc_y, acc_z) .
i want to convert (by calculation) my motor speed to acceleration data that I'm  getting from the accelometer ( in m/s^2) . By  that I can find the delta between the motor acceleration  to the accelometer meserment.
What I don't know is how to calculate from motor speed ( in RPM) to the same units that the accelerometer  gives me ( m/s^2) - I know that I need only to calculate only one axis from  the accelerometer  data.

thank you

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