Hi. The pot is working as a voltage divider. Say, You have GND at left side of the pot and Vcc (+5VDC) on the right = the pot turned to left (end position), the left pin and the center pin = 0V, pot turned to right (end position), the left pin and the center pin = 5V.. should be around 2,5V at the middle of the turn. Bye, Moebius p.s. Hmm.. just started to think.. are you sure you have a linear potentiometer?