| 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. A predicted period based on the known cam geometry is compared to the period of motion measured by the CMM. Any difference between the measured period and the actual period is an indication of inaccuracies in the CMM. |