ORIGINAL PAPER Measurement Uncertainty Evaluation Using Monte Carlo Simulation for Newly Established Line Scale Calibration Facility at CSIR-NPLI G. Moona 1 *, V. Kumar 1 , M. Jewariya 1 , R. Sharma 1 and H. Kumar 2 1 CSIR – National Physical Laboratory, New Delhi 110012, India 2 National Institute of Technology Delhi, Delhi, India Received: 26 December 2018 / Accepted: 31 May 2019 Ó Metrology Society of India 2019 Abstract: High-precision line scales are probably the most common physical standards for length measurements. They are used as reference standards, transfer standards, direct length measurement devices and ordinary measures for adjustments in length measuring machines etc. Hence, in the current scenario, a robust and reliable line scale calibration infrastructure with high precision and flexibility is of indispensable need. Keeping this in view, an improved calibration facility for line scales, ranging from 300 to 1000 mm, has been established at CSIR-NPL India by combining coordinate measuring machines, vision metrology and displacement measuring laser interferometer. The present article describes line scale (400 mm) calibration setup, measurement procedure and measurement uncertainty evaluation. Here measurement uncer- tainty evaluation is carried out by using two different approaches, law of propagation of uncertainties (LPU/GUM) and Monte Carlo simulation. The measured mean values and expanded uncertainties obtained by using the above two approaches are found to be in good agreement. Keywords: Line scale; Calibration; CMM; Vision metrology; Laser interferometer; Measurement uncertainty 1. Introduction Precise dimensional measurements play a significant role in quality control, resulting in fair trade across the globe [1]. Being the National Metrology Institute (NMI) of our country, CSIR-NPL India unceasingly aims to reconnoiter the opportunities to provide accurate, precise and traceable dimensional measurements to our customers through apex level calibration services. In addition to this, continuous upgradation of existing calibration facilities and estab- lishment of new calibration facilities is also an integral part of CSIR-NPL’s mandate. To fulfill these objectives, we established a new line scale (ranging from 300 to 1000 mm) calibration facility at CSIR-NPL India. It has been evidently observed that on finalization of a mea- surement process, there are always some doubts associated with measurement results due to a lot of assumptions in measurements such as patchy measurement procedure, unknown environmental conditions influences on mea- surement and incomplete measurand information [2]. In order to provide quantitative and qualitative assurance in the measurement process, measurement uncertainty eval- uation for calibration of line scale using this arrangement has been done by using two approaches LPU and MCS. The law of propagation of uncertainties (LPU) approach for uncertainty evaluation is described by guide to uncer- tainty for measurement (GUM). In LPU approach, it is assumed that first of all the systematic errors are redressed and standard uncertainty associated with measurement result is described as a parameter. In this approach, a model equation is formulated by using input quantities and uncertainty components associated with each of them. It is assumed that the uncertainty of measurement output will be evaluated depending upon input quantities [2, 3]. The order of steps followed in measurement uncertainty evaluation using LPU/GUM is as mentioned below. • Establish a mathematical relationship between output and input quantities in the form of model function • Compute the estimated value of input quantity • For each input estimate, compute the standard uncertainty • Covariance evaluation associated with input estimates *Corresponding author, E-mail: moonag@nplindia.org M  APAN-Journal of Metrology Society of India https://doi.org/10.1007/s12647-019-00327-7 123