A string potentiometer attached between spans of an irrigation system. The string potentiometer is mounted on a first span with the measuring cable of the string potentiometer wrapped around a hitch socket or another structural element of an adjacent span. When the two spans move out of alignment, the measuring cable extends out from the potentiometer to wrap around the hitch socket or other structural element of the adjacent span. When the two spans move closer into alignment, the measuring cable retracts within the potentiometer and unwraps from around the hitch socket or other element of the adjacent span.