accelerometer for position detection

Forum 2005-2010 (read only) Hardware Interfacing
1

i need some help
i have accelerometer MMA7260Q for detection position
i have some problems..

  1. is it normal that the distance result always have error until 10 %?
  2. is the difference in acceleration can give different result??(altough the real distance is the same one)
    thx
2

is it normal that the distance result always have error until 10 %

No the error is dependent on the implementation.

is the difference in acceleration can give different result?

No it shoudn't but in many practical implementations it might appear to be so.

There are many problems in using an accelerometer for inertial position sensing. The first is that you need to get the acceleration vector from the three axis, if the sensor is tilted in any way taking one axis will give a lower reading than is actually the case.
Next you need to integrate the acceleration, limited precision arithmetic will introduce errors.
Finally there is the noise from the sensor, this will tend to accumulate errors the longer the time between the measurement and the calibrating reference.

This is not the best way of determining position over short distances.