A sensor assembly and a computer-implemented method is described for determining the position of a reciprocating plunger (54) of a baler (12). A first sensor (64) may detect at least one location of a crank arm (30, 30a) driving the plunger (54) as the crank arm (30, 30a) rotates. A second sensor (70) may detect a rotation of a crank gear (60) that drives the rotation of the crank arm (30, 30a). A controller (34) may determine a position of the reciprocating plunger (54) relative to a baling chamber (38) based upon, at least in part, the detected crank arm location and the detected rotation of the crank gear (60).
