Servo feedback hacking

One of the big problems with the first run of my user study was that the base rotation joint on the arm had some backlash, so the servo was almost never where it claimed to be.  So I decided to do a little electronics hacking to get actual noisy feedback from the servo.  It's about like the quality of a baby monitor... you can tell that someone's saying something, but you can't quite make out what it is they're saying.  (Ok fine, it's not quite that bad, but anything less extreme just doesn't sound funny).

Anyway, the idea wasn't mine... I used some guidance posted here:
http://www.lynxmotion.net/viewtopic.php?t=3182

Here's a shot of what it looks like:

I struggled in thought for a few minutes about how to get a 2V power source with materials on hand, because our lab isn't really designed for electronics hacking.  After a few minutes I remembered that months ago I fried a servo and the pot wiper was still intact.  So I removed it and wired it up to my trusty servo controller.  I hooked it up to a volt meter and twisted the dial until it read 2V, then followed the rest of the guide and poof! 

I got it all in place, and even added some simple windowed running average software filtering to get rid of the major jitter in the voltages.  For 180 degrees of motion I get about 170 values... so almost-degree resolution isn't so bad.  Unfortunately, I still don't get a good enough alignment between the virtual arm display and the real world.  Something's still amiss.  I decided to wait until our stereo camera comes in (just a few weeks now) to do more work in this space of things.