To get traceability of the uncertainty claimed, the calibrations were performed by the Dutch National Metrology Institute (NMi VSL).
TOTAL GEOMETRIC ERROR VECTOR
The errors in the total geometric error vector of the NanoCMM are position dependent and can be calibrated and compensated by software. The standard uncertainties (expanded uncertainty = k x standard uncertainty) of these errors result from calibration measurements and contribute to the NanoCMM's standard uncertainty of a volumetric length measurement.
CALIBRATION MEASUREMENTS
Some pictures of calibration measurements are shown below.
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| Calibration measurements of the NanoCMM | |
UNCERTAINTY ESTIMATION
An overview of the standard uncertainties (in worst- and best case) that contribute to the total error vector of the NanoCMM is shown in the table below.
With these data the NanoCMM's standard uncertainty of a volumetric length measurement, due to geometric errors, will be 38 nm (2 x 38 = 76 nm expanded uncertainty (k=2)) in worst case and 13 nm (2 x 13 = 26 nm expanded uncertainty (k=2)) in best case.
These values apply to 3D objects with dimensions of the measuring volume. For the intended small products, the expanded uncertainty (k = 2) in nanometers is about 11 + 0.3×L in best case and 19 + 1.2×L in worst case, with L the measured length in mm. A typical L of 4 mm results in an expanded uncertainty (k = 2) of 12 nm in best case and 24 nm in worst case.
