Traceability enhancement in angle measurements

Traceability of angle measurements is based mainly on the standard of the plane angle – prism (polygon) calibrated at appropriate accuracy. Nevertheless, the standard (etalon) of flat angle – polygon has many restrictions for the transfer of angle unit – radian (rad) and other units of angle. It depends on number of angles formed by the flat sides of the polygon. Here is proposed a possibility to create the standard of the plane angle equal to π rad using the circular scale with the rotation axis of very high accuracy and two opposite placed precision reading instruments with appropriate alignment. Proposed method permits an implementation of π rad as primary standard angle and enables to assure a traceability of flat angle measurements at laboratory environment. Short information about the multipurpose angle measurement test bench developed is presented.     

Comparison of measurements in co-ordinate metrology

The primary output from a co-ordinate metrology system is a set of measured co-ordinates representing the locations of targets. This paper is concerned with the following issues: (a) how do we express the uncertainty associated with a set of measured co-ordinates and how can we summarise the uncertainty characteristics of a co-ordinate measuring system, (b) if two co-ordinate measuring systems measure the same set of targets, how do we assess whether the two sets of measured co-ordinates are consistent with each other, and (c) given two sets of measurements of the same set of targets, how can we obtain a combined estimate of the target locations. Any concept of traceability of co-ordinate measurements will need to provide a way of answering these questions. We show that multivariate probabilistic techniques, multivariate counterparts to those described in the Guide to the Expression of Uncertainty in Measurement, can give useful answers to these questions. We illustrate their application to laser tracker and theodolite systems.     

Traceability of DC high voltage measurements using the Josephson voltage standard

This paper introduces a new methodology for obtaining high voltage DC measurements traceability to the International System of Units (SI) at the Egyptian National Institute for Standards (NIS). The traceability has been achieved via the NIS automated 10 V DC Josephson Voltage Standard (JVS). A 100 kV DC voltage divider with a nominal voltage ratio of 10,000:1 is being used with its display in parallel with a high sensitive digital voltmeter. The traceability has been realized by calibrating this digital voltmeter via the JVS system and then it has been used to calibrate the divider display readings. Moreover, the divider ratio has been accurately calibrated using a traceable calibrator source on its high voltage side and the calibrated digital voltmeter on its low voltage side. Accurate and traceable high voltage values have been obtained associated with their expanded uncertainties. Highly improved uncertainties have been achieved using this new calibration technique.     

Development and metrological characterization of a precision force transducer for static force measurement related applications

The present paper discusses design and development of a force transducer of octagonal ring shape, which is a modified version of ring shaped force transducer. Nominal capacity of the force transducer designed and developed is 25 kN. This force transducer has been investigated for its utilization as force transfer standard for static force measurement and related applications. This force transducer is studied using dial gauge and strain gauges for its metrological characterization according to the calibration procedure based on standard ISO 376:2011/IS 4169:1988 (reaffirmed 2003) and is found to have good metrological results as compared to the existing ring shaped force transducers.     

Traceability of mass measurements in Estonia

Realization of the national mass scale for the optimal coverage of the industrial need for the mass calibrations at the Estonian national metrology institute, AS Metrosert, is described. The cost effective technical solutions to meet the calibration requirements of the advised OIML class E1 weights have been established. The traceability to the International Prototype Kilogram, the measurement capability achieved, and the results of participation in international comparisons are described in detail. The actual need for the mass calibrations in Estonia with respect to the measurement capability of the laboratory is estimated.     

Traceability and correlation in roundness measurement

A new method for the calibration of Flick standards for roundness measuring instruments has been developed through the use of a Form Talysurf stylus instrument. The method incorporates circular fits and the convolution of the standardized probe geometry over the fitted arcs using the “Kilroy's Cat” function. The method yields stable results, and an error budget documents the low uncertainty of the method. Major uncertainty contributors are the traceability of the Form Talysurf and the roughness of the Flick standard. It is shown that the tip radius has a significant effect on the results obtained in roundness measurement, even on such simple artifacts as the Flick standard. This underlines the importance of implementing a standardized tip radius. The influence of Gaussian versus 2RC filters is also documented.     

Traceability for ballistics signature measurements in forensic science

The National Institute of Standards and Technology (NIST) in collaboration with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) has developed the Standard Reference Material (SRM) 2460 Bullets and 2461 Casings. NIST has also developed a 2D and 3D Topography Measurement and Correlation System for ballistics signature measurements. This system includes stylus instruments and a confocal microscope for 2D and 3D topography measurements, and a 2D and 3D topography correlation program developed by NIST. NIST and ATF are proposing to establish a National Ballistics Measurement Traceability and Quality System using these materials. In this paper, basic concepts and specific requirements for establishing ballistics measurement traceability are introduced; three key issues are discussed that include: (1) establishing a reference standard; (2) establishing an unbroken chain of calibrations; and (3) evaluating measurement uncertainty for both the geometrical topography measurements and the optical image correlations of the ballistics signatures.     

Design and experimental evaluation of a simple and robust control setup for measurement optimization in industrial applications

Theoretical and experimental aspects are discussed concerning design and experimental setup of a simple and robust controller for optimization of on-line measurement of coating thickness, using a PC-based approach. Solutions assumed for a feedback control system are described in order to satisfy the main requirements set by this application: accuracy of operation, dynamic bandwidth, modularity of settings depending on the specific coating, handiness of using and modifying when necessary, robustness of control, and global operating reliability. Experimental results confirm that an acceptable measurement uncertainty can be achieved in tin plate coating thickness measurements by this simple displacement control system of the fiber optic measuring head.     

Realization and dissemination of units in a revised SI

The General Conference of Weight and Measures (CGPM) with its Resolution 12 has officially prospected the adoption, possibly at the next General Conference of 2011, of new definitions for kilogram, ampere, kelvin and mole using fundamental constants as reference quantities. Thus, the outlines and features of the SI after that date are worthy to be considered and a general afterthought of the metrological activity in the new situation to be attempted.The future realisations of units will greatly benefit from the accelerated endeavour to determine the relevant fundamental constants with the minimum possible uncertainty before their values are fixed by definition. In fact, many of those experiments will become realisations of units when the new definitions are adopted.To define the units by reference to fundamental constants implies to abandon the identification of the unit with its primary standard, as in the old metrological tradition. To realise a unit will definitely consist in assigning a value to a primary standard, consistent with the fixed values of the reference constants, by means of an experimental procedure, independent of a specific definition, which could even not exist. The primary standard should be suitable to dissemination by direct comparison, thus essentially stable and accessible with the highest precision, while the role of the realisation experiment would be mainly related to indirect measurements, typical of scientific activity, which involves the coherence of the unit system. The two distinct roles, of unit realisation and primary standard, correspond to different uncertainty components, of which only one is implied in dissemination activity, just aiming at compatibility of measurements of a specific quantity. Each of the two uncertainty components has a different evolution from the time of the unit redefinition.These last considerations could validly contribute in critical issues, such as deciding whether the time for a unit redefinition has come or it should be preferable to wait for new and better experiments before fixing the value of a constant. This could be the case for the kilogram redefinition.     

Some issues of traceability in the field of surface topography measurement

This paper highlights some of the reasons that surface topography measurements can have an ill-defined traceability route. Whereas the most common instruments on the shop floor are two-dimensional (2D) or profiling systems, there is a clear industrial trend towards three-dimensional (3D) surface topography instruments. Currently, there is no clear traceability route for three-dimensional measurements, and recent comparisons show alarming discrepancies between the various commercial instruments. This paper reviews these instrumental problems and highlights the need for unambiguous mathematical definitions for surface texture parameters and rigorous uncertainty evaluations. This paper also reviews some of the metrology issues that will be encountered when using three-dimensional surface texture measuring instruments to measure complex features on microsystems.     

An automatic bridge for the comparison of the impedance standards

The paper describes an automatic autotransformer bridge for comparison of the impedances (capacitance, resistance, inductance, etc.) over a wide range of values. The proposed bridge structure, algorithm and processing of two unbalance signals eliminates the influence of the cable impedance on the measurement results. The autotransformer bridge uses only one inductive divider for a wide range of measurement. Automation of the measurement is based on a variational method of the precise bridge unbalance determination. This simplifies the bridge inductive divider and twice reduces the number of its digits without decreasing of the automatic bridge accuracy. The bridge measurement uncertainty on main ranges is better than 1 ppm; the sensitivity is better than 0.01 ppm.     

A new mass & time primary standard for natural gas in China and the uncertainty evaluation

A new mass-time primary standard for high pressure natural gas, which is based on electromagnetic balance and hydraulic fast-acting valves, was set up at the beginning of 2017 in Chengdu, China. The full load of the electromagnetic balance is 3 tons and the measurement uncertainty of mass is better than 1.0g(k = 2). The opening and closing time of the hydraulic fast-acting valves can achieve 33 ms±3 ms.The operation pressure and flowrate range of the facility is (4–60)bar.a and (5–410)m³/h respectively. In accordance with the preliminary tests, the estimate uncertainty of sonic nozzles calibration is between 0.10% and 0.12%(k = 2). The operation principle, testing results and the uncertainty evaluation are presented in the paper as well as some improving ideas.     

Uncertainty of measurement by Monte-Carlo simulation and metrological reliability in the evaluation of electric variables of PEMFC and SOFC fuel cells

The aim of this work is presenting results of uncertainty of measurement calculations applied to both a low temperature PEMFC (proton exchange membrane fuel cell) and a high temperature SOFC (solid oxide fuel cell) by using Monte Carlo method simulations. The intention is correlating electric voltage, obtained in the technical literature, and energetic efficiency of the fuel cells studied in this work. In order to validate the Monte Carlo results achieved a comparison with the procedure for the evaluation of the uncertainty of measurement existing in the GUM 95 ”Guide to the Expression of Uncertainty in Measurement” (by BIPM, IEC, IFCC, ISO, IUPAC, IUPAP and OIML) is made. A reasoning of the balancing of the sources of uncertainty is presented as well. In last, it is discussed why the calibration process and traceability of the voltmeter are key factors in providing reliable metrological results in the production of electricity by fuel cell technology. This work is the first part of a broader study from which the next steps will be the validation of these presented simulations by fuel cell bench tests and the planning and development of Brazilian Conformity Assessment programs for PEMFC and SOFC fuel cells afterwards.     

Uncertainty analysis for a phase-detector based phase noise measurement system

Phase noise is an important parameter to characterise the frequency stability of oscillators and synthesised signal generators. Accurate measurement of phase noise is required for various applications in radar, communication and navigation systems. A single-channel phase-detector based phase noise measurement system is described. The system’s measurement errors and uncertainties have been analysed in details. The expanded uncertainty is about 2.7 dB for calibrating phase noise of a signal generator at 0.001–1.6 GHz for frequency offsets from 1 Hz to 100 kHz. The uncertainty budget for measuring a signal generator’s phase noise at 640 MHz is also presented.     

Newly developed standard conductance element for in situ calibration of high vacuum gauges

A new leak element, which is named as “standard conductance element (SCE)”, has been developed for in situ calibration of ionization gauges (IGs) and quadrupole mass spectrometers (QMSs). The SCE is made of a stainless-steel sintered filter with the pore size of less than 1 μm. Since the gas flow through the SCE satisfies the molecular flow condition even at the pressure up to 10⁴ Pa, some useful characteristics of molecular flow are available. The SCE is supplied to users with a calibration certificate described its molecular conductance. Users can introduce optional test gases with the known flow rate to their vacuum chamber through the SCE in their laboratories. The overview of the SCE, the calibration method and recommended practices are introduced.     

Evaluating a task-specific measurement uncertainty for gear measuring instruments via Monte Carlo simulation

Evaluating the measurement uncertainty for gears with analytical or experimental methods is usually very time- and cost-consuming. In this paper we therefore present a Monte Carlo based method for evaluating the measurement uncertainty of gear measurements on gear measuring instruments, the VCMM-Gear, which is based on the method of the VCMM for coordinate measuring machines. Necessary extensions of the mathematical model of the measurement process in order to consider the significant uncertainty influences from rotary tables, workpiece clamping and scanning are described. Additionally the statistical reliability of the evaluated measurement uncertainty and the consideration of systematic error contributions to the measurement uncertainty are discussed. Finally the results of some first verification measurements are presented, giving a reliable impression of the capability and suitability of the VCMM-Gear.     

A new vacuum interferometric comparator for calibrating the fine linear encoders and scales

A new one-dimensional laser interferometric comparator has been developed for the calibration of the fine linear encoders and scales up to 1600 mm. In the comparator, the interferometer is fully arranged in vacuum and the calibration objects are mounted under atmospheric conditions. The Abbe’s principle on the alignment of workpiece with the measuring beam is satisfied in the structure of a long measuring range. A travelling slide table, on which the calibration objects are mounted, is supported on guide rails by the air bearing and is driven through a recirculating ballscrew. The exhaust of the air bearing is guided to the exterior of the booth in which the comparator is placed. The travel of the table is measured by a reference interferometer with a beam path in vacuum shielded by an evacuated metal bellow, so that the effect of refractive index is eliminated. The laser beam is led by a polarization plane maintaining glass fiber from a self-designed stabilised He–Ne laser, which is placed in an adjacency room, to the beam inlet of the main unit. The measurement system can input the interferometer signal by the encoder signal or the scale signal, and input the encoder or scale data by the interferometer signal. The system resolution is approximately 0.8 nm and maximum travelling measurement speed is 20 mm/s at continuous measurement. The uncertainly (k=2) of measurement is approximately 30 nm in linear encoders of 500 mm length and, approximately 40 nm in scales of 500 mm, although it depends on the length and the characteristics of encoders and scales. It is successful such a high accuracy that the uncertainty of measurement system is smaller than 40 nm in encoders of 1 m length.     

Uncertainty analysis in a novel method for transformer power losses measurement

The uncertainties obtained with a novel method for measuring power losses in transformers are examined. These uncertainties are compared with those obtained by measuring power losses as the difference between input power absorbed and output power delivered and it appears that the new method does offer certain advantages with a suitable choice of instruments. Uncertainties are evaluated in compliance with the relevant CIPM recommendation adopted in 1981 and reaffirmed in 1986.     

Stereo vision for 3D measurement: accuracy analysis, calibration and industrial applications

This paper evaluates the accuracy of different camera calibration and measurement methods used in 3D stereo vision with CCD cameras. These methods are evaluated by means of several precision tests, determining their error limits under specified conditions of operation. To check the precision of such systems, a CMM and some calibration objects, such as grids, plates, spheres, etc. are used. Two practical applications are described: a cost-effective system for the measurement of free-form surfaces, able to generate CAD models and measuring programs for CMMs. The system aims to reduce some difficulties associated with stereo vision and to speed up the traditional digitizing process. The other application involves car frame measurement. A new automatic measuring system has been developed, allowing contactless car frame measurement through two rotating CCD cameras.