Traceable Calibration Method Research Articles

Application of traceable calibration for gaseous oxidized mercury in air

BackgroundThe current speciation methods for mercury (Hg) measurements are fraught with considerable uncertainty, from sample collection to calibration. High reactivity of gaseous oxidized Hg (GOM) species and their ultra-trace level presence makes them difficult to sample and calibrate. Given that improper calibration may lead to measurement biases, reliable and metrologically traceable calibration methods are required for accurately quantifying GOM in air. In the present study, we applied the recently developed calibration method based on non-thermal plasma oxidation of elemental Hg, to a commercially available Hg air speciation system for actual environmental measurements of GOM for the first time. ResultsHg species such as HgO, HgCl2, and HgBr2 were produced with trace amounts of reactant gases (oxygen and electrolytically produced chlorine and bromine) and the production was driven by plasma-assisted oxidation. The plasma oxidation efficiency of elemental Hg with oxygen was 98.5 ± 7.5 % (k = 2), while that for chlorine and bromine was 96.8 ± 6.9 % (k = 2) and 97.4 ± 9.6 % (k = 2), respectively. The calibration method was tested against the internal permeation (Hg0) source of the Tekran 2537B Hg analyzer on-field by loading HgO to different KCl-coated denuders using the plasma. GOM concentrations were measured using the Tekran speciation system. With internal calibration, concentrations were up to 9.1 % lower than those in plasma calibration, thereby emphasizing the importance of the calibration strategy. Measurement uncertainty (k = 2) further emphasizes this distinction. Internal calibration measurement uncertainty was 36.8 %, while plasma calibration boasted lower uncertainty at 13.8 %. SignificanceThe non-thermal plasma calibration strategy, as a unique and discrete calibration method traceable to the NIST SRM 3133 for ambient air GOM measurements, provide a higher level of confidence in the accuracy of GOM measurements with several advantages over other methods. Calibrations at extreme low concentrations (<100 pg) are possible with this method relevant to ambient air GOM concentrations.

Magneto-Optical Indicator Films: Fabrication, Principles of Operation, Calibration, and Applications.

Magneto-optical indicator films (MOIFs) are a very useful tool for direct studies of the spatial distribution of magnetic fields and the magnetization processes in magnetic materials and industrial devices such as magnetic sensors, microelectronic components, micro-electromechanical systems (MEMS), and others. The ease of application and the possibility for direct quantitative measurements in combination with a straightforward calibration approach make them an indispensable tool for a wide spectrum of magnetic measurements. The basic sensor parameters of MOIFs, such as a high spatial resolution down to below 1 μm combined with a large spatial imaging range of up to several cm and a wide dynamic range from 10 μT to over 100 mT, also foster their application in various areas of scientific research and industry. The history of MOIF development totals approximately 30 years, and only recently have the underlying physics been completely described and detailed calibration approaches been developed. The present review first summarizes the history of MOIF development and applications and then presents the recent advances in MOIF measurement techniques, including the theoretical developments and traceable calibration methods. The latter make MOIFs a quantitative tool capable of measuring the complete vectorial value of a stray field. Furthermore, various scientific and industrial application areas of MOIFs are described in detail.

Metrology Challenges in Quantum Key Distribution

The metrology of the QKD devices and systems grows increasingly important in recent years not only because of the needs for conformance and performance testing in the standardization, but more importantly, imperfect implementation of the devices and systems or deviations from the theoretical models, which could be exploited by eavesdropper, should be carefully characterised to avoid the so-called side channel attack. In this paper, we review the recent advances in many aspects of the QKD metrology in both fibre based QKD and free space QKD systems, including a cutting edge metrology facility development and application, traceable calibration methods, and practical device characterising technologies, all of which have been contributed by the metrology communities and relative institutions.

Developments and Progress in Non-contact Eye Tonometer Calibration

Abstract This paper focuses on the problematic of intraocular pressure (IOP) measurements, performed by non-invasive methods. More specifically, the devices that are connected with the presented finding are non-contact tonometers that use concentrated air stream and optical sensors to determine the IOP within a human’s eye. The paper analyzes various influential factors that have an effect on the determination of the IOP values originating from the patients themselves and from the non-contact tonometer devices. The paper furthermore elaborates on the lack of independent methods of calibration and control of these devices. In order to fill this gap a measurement standard device that is capable of calibrating and testing these devices with traceability to the basic SI unit is presented. A detailed characterization and the determination of the expected uncertainty of the device are provided. By introducing an independent and traceable calibration method and control of non-contact tonometers into the clinical practice, the reliability of the measured IOP that is the primary indicator of glaucoma can be improved.

Novel Broadband Calibration Method of Current Shunts Based on VNA

Usually high wideband ac current and harmonics measurements are accurately achieved in industry and laboratories by using high accuracy shunts or standard shunts. For particular applications, such as power and transient measurements, it is mandatory to evaluate the shunt impedance phase and magnitude according to the frequency bandwidth of interest before to measure the current with such sensors. High electrical current shunt beyond 1 A is calibrated in magnitude up to 100 kHz and in phase angle up to 200 kHz only by a few National Metrology Institutes. The existing traceable measurement methods to characterize these sensors are limited in frequency to 100 kHz, with expanded uncertainties of the ac–dc difference (magnitude) and the phase angle of more than $5 \times 10^{-6}$ and $62~\mu $ rad at 100 kHz, respectively. A new traceable calibration method to measure and characterize current shunts at high frequencies is presented in this paper. This measurement method is based on the use of a vector network analyzer. The measurements are presented up to 60 MHz, but theoretically, the presented method does not exhibit a specific frequency limitation. Only the characteristics of the shunt under study can impose limitation in practice. While uncertainties are higher than those provided by the existing methods, the method presented in this paper is the only method able to perform in one step a broadband and simultaneous measurement of the magnitude and phase of current shunts up to few megahertz with acceptable uncertainties.

Estimating dynamic mechanical quantities and their associated uncertainties: application guidance

Recently several European National Measurement Institutes have established traceable calibration methods for dynamic mechanical quantities, e.g. dynamic force, torque and pressure. However, the use in industry and elsewhere of dynamic calibration information provided on certificates is not straightforward. Typically it is necessary to employ deconvolution techniques to obtain estimates of measurands, and the deconvolution method itself and the associated algorithms are sources of uncertainty that must be included in uncertainty budgets. There is a need for practical guidance for end users on how to use the newly-available dynamic calibration information. To this end we set out an approach to the evaluation of uncertainties associated with dynamic measurements that we believe covers the most relevant cases. The methods have been embodied in publicly-available software and we show how they can be used to tackle some example problems. We believe that the methods lead to more reliable estimates of the relevant measurands and their associated uncertainties.

Traceable Size and Size Distribution Calibrations of Nanoparticles

Quality control of nanoparticle production processes requires traceable calibration methods for size and size distribution which are presented and discussed in this article. The main focus is on the one hand the application of small-angle X-ray scattering for an integral measurement of nanoparticles in liquid suspension and on the other hand scanning electron microscopy in transmission for a microscopic measurement method of nanoparticles prepared on a substrate. In addition, characterization by scanning probe microscopy is covered.

Traceable calibration of impedance heads and artificial mastoids

Artificial mastoids are devices which simulate the mechanical characteristics of the human head, and in particular of the bony structure behind the ear. They are an essential tool in the calibration of bone-conduction hearing aids and audiometers. With the emergence of different types of artificial mastoids in the market, and the realisation that the visco-elastic part of these instruments changes over time, the development of a method of traceable calibration of these devices without relying on commercial software has become important for national metrology institutes. This paper describes commercially available calibration methods, and the development of a traceable calibration method including the traceable calibration of the impedance head used to measure the mechanical impedance of the artificial mastoid.

A traceable calibration method for spectroscopic ellipsometry

A method for calibrating the spectroscopic ellipsometry by X-ray reflectivity is presented. As an indirect method，spectroscopic ellipsometry does not have the traceability because the measured film thickness is dependent on its optical constant. In contrast，at the grazing angle，the X-ray reflectivity can be used to measure the absolute thickness of thin film with sub-nanometer precision，and is independent of the optical constant. Five SiO2 films were deposited on the substrate of single crystal silicon with the thickness of 2 nm，18 nm，34 nm，61 nm，and 170 nm，respectively. The results of spectroscopic ellipsometry and X-ray reflectivity were well fitted by a liner equation with slope of 1013±0013 and its intercept was set to zero，which means this calibration method is valid for spectroscopic ellipsometry in the determination of the thickness of thin films.

Traceability and Verification of Interharmonic Generators in Support of Low-Frequency Immunity Testing (IEC61000-4-13)

A description of the interference immunity testing of electrical products is given, and the need for traceable calibration methods of the associated testing generators is described. A presentation of three analysis techniques to verify the respective testing modes of immunity testing generators is given, together with typical uncertainties. A deconvolution method developed for the phase characterization of the analog-to-digital converter (ADC) used in this work is reported. A least squares algorithm for the piecewise analysis of the International Electrotechnical Committee (IEC) flat-top waveform is presented in the Appendix.

Cryogenic ultrasonic flow measurement—an enabling technology for LNG production, storage and transportation

Liquefied natural gas (LNG) is becoming an increasingly important energy commodity with the declines in conventional oil reserves. The economics of LNG depend on the use of cost effective production, storage and transportation systems, which can involve use of shared facilities. For example, shared storage and berthing facilities can result in massive cost savings for LNG producers. The potential cost savings associated with shared storage or transportation of LNG can only be realised if each partner can be assured that they are getting their fair share of the final revenue, i.e. reliable systems for production allocation and custody transfer are required. Previously, tank level based volumetric measurement has been the standard in LNG measurement; however, such systems are dependent on the very infrastructure that can be eliminated in shared transportation and storage systems. What is needed for shared facilities is a reliable method of in-line LNG metering. Up until recently, in-line metering of LNG had not been used for allocation or custody transfer owing to a lack of qualified technologies capable of accurate measurement. The two major challenges are to produce a metering technology capable of reliable operation at cryogenic temperatures and to devise a traceable calibration method appropriate for the conditions of operation. This paper describes the development of reliable ultrasonic meters designed for high accuracy measurement of LNG and addresses the issues that could arise as a result of the differences between calibration and field conditions. Data is presented demonstrating the performance and robustness of transducers specially designed for cryogenic operation. Details are provided of a method for transferring laboratory calibration using water to LNG application conditions with minimal uncertainty. The paper includes a case study related to the use of these meters for allocation into shared storage at the Qatar Gas common facilities project. Prior to selection of the meters for this application the project partners undertook an evaluation of the ultrasonic technology at the Kenai LNG plant in Alaska alongside Coriolis flow metering technology. The aims of this field qualification testing are described and results presented.

Comparison of traceable calibration methods for primary photovoltaic reference cells

The calibration of photovoltaic reference cells used as primary laboratory standards for the calibration of photovoltaic devices needs to be traceable to international radiometric standards and SI units. As a contribution to the development of an international standard this paper describes three methods for the calibration of primary photovoltaic reference cells, establishing two independent traceability chains. The solar simulator method is traceable via a standard lamp to the international irradiance scale whereas the global sunlight method and the modified global sunlight method are traceable to the world radiometric reference. The calibration values obtained by the three methods agree with each other within their respective uncertainties and with the world photovoltaic scale within ± 0·8%. Copyright © 2005 John Wiley & Sons, Ltd.