Sounds like an inherent characteristic of analog sensors (unless it's a smart sensor with built in logic). One way for you to control the output is to, at some point between sensor and animation, reduce the precision - i.e. deliver a more inaccurate, but more even, value to your animation.

There's probably better way to do it though, like adding resitors or capacitors, or whatnot (I have no clue myself...) to your circuit which will even the current a bit.

A link to get you started: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1255301852

a__g, thanks for your reply. I tried to add resistors, but no change. I found this Arduino smoothing code, but will need to add it to Firmata.  http://arduino.cc/en/Tutorial/Smoothing 

I used smooth function that works. code and description is available on my blog  http://www.arturjanas.co.uk/archives/412 

having the similar problem with pressuresensors to analog inputs. thx for posting this, will try it!

polklemme