In the three-coordinate calibration results of PC-DMIS software, the effective diameter d and stdDev values of the probe will appear. Generally, we require stdDev≤0.003. My humble opinion on the significance of this stdDev requirement is as follows, please advise:

Personally, when measuring the standard sphere at five points, due to the influence of precision and delay error, the actual radius from the fitting center of the measured five points to the five points is different. In order to express the dispersion degree of radius data from the fitting center to each point, the standard deviation stdDev (algorithm omitted) is used. The smaller stdDev is, the better the consistency of the radius data from the fitting center to each point is and the higher the accuracy is.

According to the training manual, stdDev means the calibrated shape error, which is probably the measurement of the outline of the standard sphere, which is consistent with the fitting radius in the sense.