Uncertainty due to experimental conditions in co-ordinate measuring machines

Any measurement method of a physical quantity cannot provide an exact unequivocal result owing to the infinite amount of information necessary to characterize fully both the physical quantity to be measured and the measuring process. Therefore, a quantitative indication of the quality of a measurement result needs to be given to enable its reliable use. Uncertainty is one such indication. Provision of incorrect uncertainty statements for measurements performed by a co-ordinate measuring machine (CMM) may lead to very serious economic implications. In this study, the uncertainty of CMM measurements is estimated by a single parameter accounting for both systematic and random errors. The effects that environmental conditions (temperature), discretionary set-up parameters (probe extension, stylus length), and measuring plan decisions (number of points) have on uncertainty of measurements are then investigated. Interactions between such factors are also shown to be significant.