Impossibility to change the rate of the accelerometer

Question

I have to collect accelerometer data from my Android phone, so I have made a little program to do that.

After some tests, I have found that my Nexus S accelerometer\

Answer 1

Don't connect your phone to a PC via USB while taking data because during collection data is logged in the SD card only. When the phone is connected to PC via USB no file can be saved in SD card.

So try disconnecting the USB while collecting the data.