Android :: Low Accuracy Of The Accelerometer Sensor?

We are writing an application that uses acceleration sensor data to plot phone's movement in 3D. We are finding gross inconsistencies in the actual data output by the sensor. Also, sampling rates vary greatly from 8 to 200 millis. (using System.currentTimeMillis())

Specifically, when we try to draw a circle with G1 flat on the table all the time (filtering out gravity accel 9.8), most of the time we would get a plot of phone's position that is not a circle at all. Lots of times, it would be close to a straight line. Sometimes, it would start drawing an arc, but would not close the circle shooting off in a random direction.

We tried to eliminate the time variable, by substituting a constant time sampling rate (10 millis) to calculate phones position, but the result was very close to what we had before (shapewise). Also, the acceleration in Z direction when the phone is displaced lying flat on a table (XY plane) varies too by +/- 2 units which is a lot.

I do not think it is an error in our code, as we have checked it many times. If there were an error indeed and the accelerometer worked properly, we would see a consistently wrong depiction of the phone's movement. Unfortunately, repeating the same movement (circle) would produce sometimes wildly differently shaped plots.

It all comes down to us wanting to know if that is indeed the case that the G1 accelerometer is very unreliable and inconsistent device when used for more or less precise measurements? Is there some documentation/facts paper that would tell us just how reliable accelerometer is?