A plurality of twine tensioner arms are mounted at evenly spaced locations across the baling chamber of a large square baler for pivoting vertically, against a yieldable bias, between upper and lower extreme positions. Each tensioner arm carries a tensioned twine strand associated with a double-knot tying device. A rotary potentiometer is coupled, by a follower arm, for sensing pivotal movement of each tensioner arm and sends out a corresponding electrical signal to an electronic controller which processes the sensed arm position together with other stored information and sends out a signal for energizing a display showing the relative positions of the arms and/or for energizing a warning device for apprising an operator that a mistie has occurred, is about to occur or that a twine tensioner setting has to be changed.
