Abstract: A stylus (15) for contacting a workpiece (13) to sense its position is suspended on a movable member (16) within a fixed housing (10). The suspension is by means of three connecting units (20, 30, 40). Taking the connecting unit (20)as an example, the movable member (16) is connected to an intermediate member (22) by a first pair of links (21), while the intermediate member (22) is connected to the fixed housing by a second pair of links (23). The pairs of links are rigid in tension and compression so as to prevent rotation of the stylus about a respective one of the three orthogonal axes X, Y, Z. Nevertheless, the links permit translational movement along all three axes. The similar connecting units (30, 40) likewise permit translation on all three axes, while preventing rotation about a respective one of the axes.