@larryd
I will switch to the digital pins instead of Analog pins. Though I am not sure why this is better. Is it because the sampling will happen at fixed intervals ? Thanks 
@wvmarle
Thanks. Your second advice to keep all data and do a post processing to get the actual contact time, seems to be a great approach - without loosing any of the accuracy.
Where is this project headed? What are you actually trying to measure? Do you need to record the time the foot touches and the length of time it remains on the cylinder? Are you wanting to measure all 4 feet?
Yes we need to record the time the foot touches and the length of time it remains on the cylinder.
We are measuring only on the two hind feet. One of the feet would be injected with a medicine, while the other would serve as a control feet.
I have attached a PDF with a similar experiment setup (see page 3-4 for the instrumentation detail). However, while this experiment uses 6 rats at a time, we do it on one rat at a time.
Where is the 5v source, and how are the electrode and the metal cylinder wired. What goes to 5v, what goes to ground and what goes to the Arduino.
The attached PDF gives a schematic for 6 rats but we will simplify it to work only for a single rat.
04DDR28(NewM)93.pdf (285 KB)