You definitely should connect Vdd and Vss the same way on all pots. The drawing has it wrong. I think the best way to go would be that: Vdd (+) is at the clockwise extreme of the pot's travel, and Vss (-) is at the Anti-clockwise extreme. You can get it to work the other way, but you'll need to use scaling, and it's just not the right way to do it!! - I've seen that drawing a few times in the past, and it seems it is a hasty sketch, intended mostly to show the star pattern, but generally ends up creating confusion about Vdd and Vss polarity!! The second one is correct. Vdd is Positive (+5 Volts), Vss is negative. (0 Volts) The terms themselves relate to their use with FET devices. (Perkaps a wiki entry would help?)