Abstract: Devices for verifying the dimensional accuracy of a measuring instrument are provided. In one embodiment, a verification block has a substantially planar surface and a known nonplanar surface adjacent thereto. During verification, a probe attached to the CMM moves along the nonplanar surface while simultaneously contacting the planar surface and measures the features of the nonplanar surface. Any difference between the measured features and the known features of the nonplanar surface is an indication of inaccuracies in the CMM. Other embodiments of the invention include structures which compare CMM measured readings with known readings by an encoder as it moves along a linear scale. In another embodiment, the measured readings are compared to readings provided by opto-electric switches. In still another embodiment, a cam is rotatably mounted to the end of the probe of the CMM and moves the probe along the z axis as the cam moves along a surface.

Abstract: A coordinate measuring machine includes a support structure, an articulated arm having a first end pivotally connected to the support structure and a second end that is movable in a horizontal plane. A Z-ram assembly is mounted to the second end of the articulated arm. The Z-ram assembly includes a Z-ram housing and a probe that is vertically movable with respect to the Z-ram housing. The probe is movable within a measurement volume defined by the articulated arm and the Z-ram assembly. The coordinate measuring machine further includes a measuring assembly for determining coordinates of the probe in the measurement volume. The articulated arm preferably includes first and second arm assemblies that have a parallelogram configuration to prevent substantial rotation of the Z-ram assembly as the articulated arm is moved in the horizontal plane. The angles of the articulated arm are preferably measured using a sensor which includes a pattern of parallel, straight grating lines.