Study in determining of junction point value for shifting measurement method on line scale calibration in SNSU BSN

Abstract

Abstract Calibration of line scale in the National Standards Measurement-National Standardization Agency in Indonesia (SNSU-BSN) is carried out by using one dimensional measuring machine (SIP machine) which traceable to the laser interferometer or laser interferometer itself. Although line scale calibrated using laser interferometer, the system needs SIP machine as linear movable carriage and SIP table as the base on line scale. Length measurement of the SIP machine covers only up to 400 mm and for line scale above 400 mm, measurement can be extended to 1000 mm using shifting methods. When the scale is shifted, the position of the last point of previous measurement might not be on the same position, even though it has been well alignment for the second measurement. There is an error due to a junction between position scale on the first measurement to the second measurement. This error is added to the uncertainty budget as a junction point error because of the shifting. This paper described how to determine an appropriate value that should be attached on the uncertainty budget. It was found the error value of junction point due to shifting method in line scale calibration is 0.42 µm and the expanded uncertainty of line scale calibration for 1000 mm is 2.5 µm.