The NIST M48 coordinate measuring machine (CMM) was used to measure the average diameter of two precision, silicon spheres of nominal diameter near 93.6 mm. A measurement technique was devised that took advantage of the specific strengths of the machine and the artifacts while restricting the influences derived from the machine's few weaknesses. This effect resulted in measurements with unprecedented uncertainty levels for CMM style instruments. The results were confirmed through a blind comparison with another national measurement institute (NMI) that used special apparatus specifically designed for the measurement of these silicon spheres and employed very different measurement techniques. The standard uncertainty of the average diameter measurements was less than 20 nanometers. This paper will describe the measurement techniques along with the decision-making processes used to develop these specific methods. The measurement uncertainty of the measurements will also be rigorously examined.
Proceedings Title: Proceedings of SPIE on Recent Developments in Traceable Dimensional Measurements II, Jennifer E. Decker, Nicholas Brown, Editors November 2003
Conference Dates: August 4, 2003
Conference Location: San Diego, CA
Conference Title: Coordinate Measurements
Pub Type: Conferences
accuracy, CMM, comparison, silicon sphere, uncertainty