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Measurements are of paramount importance in industry and other areas of importance to society. They are used to determine the characteristics of processes and products, to control and regulate processes, to decide on the acceptable quality of products, etc. To ensure the quality of measurements, we have to calibrate measuring devices regularly. In our laboratory - the holder of the national length standard, we mainly calibrate high-precision standards from accredited laboratories. As the demands on the accuracy of measurements are constantly increasing, we are also forced to continuously improve the accuracy of our calibration procedures. This article presents the development of methods for calibrating the diameter of ring gauges, which represent an important standard for calibrating measuring instruments for measuring internal dimensions. The main objective of this development is to reduce the measurement uncertainty based on a scientific investigation of all influencing parameters. The presented study focuses in particular on the control and reduction of the influence of geometric anomalies of the calibrated rings on the measurement uncertainty during calibration. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the measurement capability of laser interferometry for calibrating high-resolution measuring systems, focusing on potential errors that need to be carefully controlled to ensure adequate metrological traceability. The primary scientific research focus of our National Dimensional Metrology Laboratory is the development of metrological applications for industry, with ongoing improvements in calibration procedures for measuring machines and tools. Through a review of possible error sources, an innovative approach to reducing the most significant factors is proposed. This is specifically applied to the following calibration cases: field calibration of coordinate measuring machines, and laboratory calibration of precision probes and line scales. Instrumental and environmental errors can be effectively mitigated by using periodically calibrated laser interferometers in well-controlled air conditions, ensuring an uncertainty of 0.2 μm/m. Most geometrical errors can be minimized by precise adjustments to the interferometry and positioning systems, achieving an uncertainty of 0.3 μm/m. However, errors caused by temperature differences in the material along the measuring path remain the most influential. These arise due to the high expansion coefficient of the material and some uncertainty in its properties. After several hours of temperature stabilization, using three temperature sensors along the displacement range for software compensation, temperature differences still contribute significantly to measurement uncertainty. For example, the error is 0.5 μm/min in the case of line scale calibration and 1.1 μm/m for coordinate measuring machine calibration. [ABSTRACT FROM AUTHOR]

Highest-level traceability of dimensional measurements in the Laboratory for Production Measurement (LTM) at University of Maribor (a nationally designated metrology institute), consistent with the Mutual Recognition Arrangement by the International Committee for Weights and Measure, is presented. A reliable primary laser frequency standard is important for national chains of industrial calibrations and measurements. Laser stabilization technique and calibration procedure for investigating the stability and reproducibility of HeNe lasers, used for interferometry length measurements, are described. Along the international interlaboratory comparisons, the calibration accuracy is periodically verified using a highly stable interferometer laser, by a simple method presented in this contribution. [ABSTRACT FROM AUTHOR]

Precise calibration of quartz line scales is very important for assuring traceability of microscopic measurements. Very significant influence in calibration uncertainty budget is represented by uncertainty of line centre detection. Line centre is usually detected through video signal processing using different types of algorithms. This paper is presenting calibration procedure that was developed in the Laboratory for Production Measurement at the Faculty of Mechanical Engineering in Maribor. It is focused in uncertainty analysis and especially in the influence of line scale contamination on determination of line centre position. Different types of line scale contamination like dirt spots, scratches, line edge incorrectness, and line intensity were simulated in order to test the ability of the line centre detection algorithm to eliminate such influences from the measurement results. [ABSTRACT FROM AUTHOR]