Uncertainty Evaluation in calibration of Engineer’s Steel Rulers and Measuring Tapes; GUM and Monte Carlo Methods

Engineer’s steel rulers and measuring tapes are considered versatile dimensional measuring tools for many industrial applications. Calibrations of these tools are carried out by comparing their scales with reference length standards. The reference standards can be geodetic baselines provided by a laser interferometer system or linear encoder that integrated in well-designed guideway. This work aims to study not only the calibration process for steel rulers and measuring tapes but also the affecting parameters on this process and the assessment of associated uncertainty by different evaluation methods. In this paper, a 1000 mm engineer’s steel ruler and 5000 mm measuring tape are calibrated. A calibration system of precise guideway provided by linear encoder of 1 µm resolution are used. Associated uncertainties have been estimated based on GUM and Monte Carlo Simulation (MCS) methods. The parameters that may affect the calibration processes are carefully studied through the uncertainty evaluation. Expanded uncertainties of about 20 µm and 80 µm for calibration of 1000 mm engineer’s steel ruler and 5000 mm measuring tape respectively are achieved. This study presents two issues. (1) it is first documented work in the study of uncertainty assessment and related parameters in this calibration type. (2) application of Monte Carlo Simulation (MCS) method in uncertainty evaluation in calibration of these tools.