A sensor assembly and method is described for determining the position of a reciprocating plunger of a baler. A first sensor may detect at least one location of a crank arm driving the plunger as the crank arm rotates. A second sensor may detect a rotation of a crank gear that drives the rotation of the crank arm. A controller may determine a position of the reciprocating plunger relative to a baling chamber based upon, at least in part, the detected crank arm location and the detected rotation of the crank gear.
