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Unformatted text preview: )2 with p = n ∑ pk n −1 The standard uncertainty uws caused by the dispersion of the influences roughness uRZ, form deviation uF, temperature uT and elasticity uE between series workpiece and calibrated workpiece can be calculated by s( p k ) =
2 2 2 2 u ws = u RZ + u F + uT + u E (4) with the assumption that the influences do not correlate. For rigid workpieces the influence uE can be disregarded. For expansion of the series of observations (p1, p2....pk) with un-calibrated workpieces the factors uF and uRz can be disregarded, too. In coordinate metrology measurement results are also related to the reference temperature of 20 °C according to ISO 1. If the temperature of the workpiece differs from the reference temperature the workpiece expands and causes geometrical deviations. Current CMMs are capable to record the workpiece temperature and to compensate the thermally caused expansion of the workpiece, if the expansion coefficient αWS is known. Beside the deviation of the workpiece temperature (∆TWS) and the uncertainty of the temperature measurement (u(∆T)) the measurement uncertainty is caused by the uncertain...
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