range of accelerometer?

I've been playing with an app that show the accelerometer readout. I noticed that when I shake the device as hard as I can, it only reads a max of 2.0

I guess this is 2.0 G forces or something. It hit's 2.0 no matter how hard I move it.

I'm digging into the code now, and looking to show the graph in greater detail, but was just wondering if there is a limit to what the accelerometer will read or is there a range setting?