Noisy Accelerometer

[jee7s]

You may have neither.

If there is a lot of vibration, you could expect there to be added interference (it isn't strictly speaking noise) from the vibrations. You can limit this by isolating the chip using some foam.

You will certainly have noise, simply because you have a wire in the open. The source of that noise could be from your environment, or it could be from your motors if you have mounted it on the robot. Again, the interference from the motor PWM signal isn't strictly noise, but it will look like noise. To isolate this, you can use a shielded cable, like coax.

Another potentially more likely problem is that your sample rate is improper. If you are sampling too slowly without band limiting (filtering) the input signal, you'll run into a phenomenon called aliasing. So, make sure your sample rate is set to match the rate that you are actually gathering data. There is an analog filter on the board, but you may want to build one of your own. The cutoff of that filter will go a long way to determining your sample rate.

-Jeff Erickson, FRC 41