tailieunhanh - Uncertainty and Dimensional Calibration Episode 3

Tham khảo tài liệu 'uncertainty and dimensional calibration episode 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Volume 102 Number 6 November-December 1997 Journal of Research of the National Institute of Standards and Technology Customer Artifact Geometry Ring gages have a marked diameter and we measure only this diameter. The roundness of the ring does not affect the measurement. We do provide roundness traces of the ring on customer request. Summary The uncertainty budget for ring gage calibration is shown in Table 8. The expanded uncertainty U for ring gages up to 100 mm diameter k 2 is U rnm L. 8. Gage Balls Diameter Gage balls are measured directly by interferometry or by comparison to master balls using a precision micrometer. The interferometric measurement is made by having the ball act as the spacer between two coated optical flats or an optical flat and a steel platen. The flats are fixtured so that they can be adjusted nearly parallel forming a wedge. The fringe fraction is read at the center of the ball for each of four colors and analyzed in the same manner as multi-color interferometry of gage blocks. A correction is applied for the deformation of the flats in contact with the balls and when the steel platen is used and for the phase change of light on reflection from the platen. Master Artifact Calibration Master balls are calibrated by interferometry using the ball as a spacer in a Fizeau interferometer or by comparison to gage blocks. The master ball historical data covers a number of calibration methods over the last 30 years. An analysis of this data gives a standard deviation of mm with 240 degrees of freedom. Since these measurements span a number of different types of sensors multiple sensor calibrations systematic corrections and environmental corrections there are very few sources of variation to list separately. The only significant remaining sources are the uncertainties of the frequencies of the cadmium spectra which are negligible for the typical balls 30 mm calibrated by interferometry. We take the standard .