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Abstract: According to documentary standards for the performance evaluation of laser trackers (LT), long length reference artifacts are required. In this paper, we discuss the design, construction, and calibration of a long length artifact
called a step gauge of nests (SGN). The SGN has several nests in line in which to place the LT probe; the two extreme nests of the SGN are at a distance of 3 m, approximately. The documentary standards establishes that the gauge’s length shall be
known no matter the orientations it takes. However, for long gauges, factors like gravitational force, fixturing forces, change in the environmental conditions, among others, deform the gauge, and its length changes when its orientation changes. To
evaluate these factors, we use a finite element simulation of the SGN in the design stage to predict such deformations (mainly length variations between the two extreme nests). The simulation takes into account the used material, its stiffness, straightness,
distribution of the nest’s weight, and geometry’s change of the SGN to reduce the variations in its length. For the construction stage, we describe how the SGN was manufactured and how using high module carbon fiber reduces the influence of the temperature
factor. The results of the finite element simulation show a length variation of around 20 μm between the horizontal and vertical SGN positions. That variation was validated with the calibration results of two different methods. The first uses
the line of sight (LOS) method, which involves the same LT under evaluation. The second uses an accurate CMM, using the overlap method for calibration. The traceability of the LOS method is accomplished with the wavelength calibration of the LT interferometer
while the overlap method uses a CMM evaluated with a laser interferometer with calibrated wavelength.
References:
[1] ASME B89.4.19-2006 Performance Evaluation of Laser-Based Spherical Coordinate Measurement Systems, ASME International. [2] ISO 10360-10:2016 Geometrical product specifications (GPS) - Acceptance and reverification tests for coordinate measuring systems (CMS) - Part 10: Laser trackers for measuring point-to-point distances. [3] VDI/VDE 2617-10:2011 Accuracy of Coordinate Measuring Machines - Characteristics and Their Checking - Acceptance and Reverification Tests of Laser Trackers. [4] Sawyer D, Parry B, Phillips S, Blackburn C, Muralikrishnan B., “A model for geometry-dependent errors in length artifacts”, J Res Natl Inst Stand Techno, 117:216, 2012. [5] Icasio-Hernandez O, Trapet E, Arizmendi-Reyes E, Valenzuela-Galvan M and Brau A, “Overlap method for performance evaluation of coordinate measurement systems and the calibration of one-dimensional artifacts,” Meas Sci Technol, 2020. [6] Wang L, Muralikrishnan B, Lee V, Rachakonda P, Sawyer D, Gleason J, “Methods to calibrate a three-sphere scale bar for laser scanner performance evaluation per the ASTM E3125-17”, https://doi.org/10.1016/j.measurement.2019.107274 [7] Muralikrishnan B, Sawyer D, Blackburn C, Phillips S, Borchardt B, Estler WT, “ASME B89.4.19 2009 Performance Evaluation Tests and Geometric Misalignments in Laser Trackers,” J Res Natl Inst Stand Technol, 114(1):2135, 2009 Feb 1. doi:10.6028/jres.114.003 [8] Loser R, Kyle S, “Alignment and field check procedures for the Leica Laser Tracker LTD 500,” In: Boeing Large Scale Optical Metrology Seminar, 1999. [9] Hudlemeyer A, Meuret M, Sawyer DS, Blackburn CJ, Lee VD, Shakarji CM, “Considerations for design and in-situ calibration of high-accuracy length artifacts for field testing of laser trackers,” Journal of the Coordinate Metrology Society Conference, 10(1):26-32, 2015. [10] ISO 15530-3 2011, Geometrical Product Specifications (GPS) coordinate measuring machines (CMM): Technique for determining the uncertainty of measurements Part3: Use of calibrated workpieces or measurement standards, ISO, 2011.
Abstract:
The physical model of the spectral responsivity of trap detectors consists of multiple parameters such as the internal quantum efficiency and the spectral reflectance. In some measurement models, the spectral reflectance of trap detectors
is approximated by fitting a wavelength dependence equation which does not consider the effect of the oxide thickness of the silicon photodiode. To analyze the uncertainty due to the oxide thickness variation, a thin film reflectance model is set
up in the Standards and Calibration Laboratory (SCL) for the evaluation of the spectral reflectance of trap detectors. The model is based on the Fresnel coefficients of a three-layer thin-film structure which consists of air and a thin-film oxide
layer on a silicon substrate. The reflectance model was implemented as user-defined functions to calculate the spectral reflectance at different oxide thicknesses. It was also integrated with the SCL’s MCM program to evaluate the uncertainty of the
spectral responsivity of trap detectors.
References:
[1] C.M. Tsui, Brenda H. S. Lam, Brain H. T. Lee “Interpolation of Spectral Responsivity of Trap Detectors and Evaluation of Measurement Uncertainties Using Monte Carlo Method”, to be published in NEWRAD2020 conference proceedings. [2] L. Werner, J. Fisher, U. Johannsen and J. Hartmann, “Accurate determination of the spectral responsivity of silicon trap detectors between 238 nm and 1015 nm using a laser-based cryogenic radiometer”, Metrologia, 2000, 37, 279-284. [3] I. H. Malitson, “Interspecimen Comparison of the Refractive Index of Fused Silica”, Journal of the Optical Society of America, Vol. 55, Issue 10, pp. 1205-1209 (1965). [4] G.E.Jellison Jr., “Optical functions of silicon determined by two-channel polarization modulation ellipsometry”, Optical Materials, Volume 1, Issue 1, January 1992, pp 41-47. [5] E. Hecht, Optics, Fourth Edition, Addison-Wesley. [6] T.R. Gentile, J.M. Houston and C.L. Cromer, “Realization of a scale of absolute spectral response using the National Institute of Standards and Technology high-accuracy cryogenic radiometer”, Applied Optics, 35, 4392-4403, 1996.
Abstract: This paper presents the procedure developed at SXL for the calibration of loop antennas for test frequencies from 9kHz to 30MHz in accordance with CISPR 16-1-6:2014+AMS1:2017. The background, measurement modal and uncertainty components are
introduced and discussed. The expanded measurement uncertainty is estimated as 1.2 dB.
References:
[1] International Standard CISPR 16-1-6:2014+AMD1:2017: Specification for radio disturbance and immunity measuring apparatus and methods—Part 1-6: Radio disturbance and immunity measuring apparatus—EMC antenna calibration. [2] F. Pythoud, M. Borsero, D. Bownds, S. Çakir, M. Çetintas, K. Dražil, D. Gentle, D. Giordano., S. Harmon, J. Kupec, Y. Le Sage, B. Mühlemann, M. Ulvr, G. Vizio and D. Zhao, “EURAMET Supplementary Comparison: EURAMET.EM.RF-S27 Antenna factor for Loop Antennas,” Metrologia, vol. 51 (1A) 01007, Jan 2014. [3] M. J. Alexander, M. J. Salter, D. G. Gentle, D. A. Knight, B. G. Loader, K. P. Holland, “Calibration and use of antennas, focusing on EMC applications”, Measurement Good Practice Guide No. 73, National Physical Laboratory, December 2004. [4] M. L. Crawford, “Generation of Standard EM Fields Using TEM Transmission Cell”, IEEE Transaction on Electromagnetic Compatibility, vol. EMC-16, No. 4, Nov 1974. [5] J. C. Tippet, D. C. Chang, “Radiation Characteristics of Dipole Sources Located Inside a Rectangular, Coaxial Transmission Line,” NBSIR 75-829, Jan 1976. [6] JCGM, “Evaluation of measurement data — Guide to the expression of uncertainty in measurement,” JCGM 100:2008.
Abstract: The Standards and Calibration Laboratory (SCL) in Hong Kong has developed a system for calibration of quarter- inch working standard (WS3) microphones which automates the measurement process and generates digital calibration
certificates (DCCs) to meet the growing demand for microphone calibration services in Hong Kong. This paper describes (i) the method of determining the pressure sensitivity of a microphone combination unit from 20 Hz to 20 kHz by the comparison technique
in accordance with the International Standard IEC 61094-5, (ii) the measurement model and uncertainty evaluation, and (iii) the automatic system which facilitates the calibration process and generation of a digital calibration certificate.
References:
[1] IEC, “Electroacoustics – Measurement Microphones, Part 5: Methods for Pressure Calibration of Working Standard Microphones by Comparison”, IEC 61094-5:2016. [2] IEC, “Electroacoustics – Octave-band and Fractional-octave- band Filters, Part 1: Specifications”, 61260-1:2014. [3] JCGM, “Evaluation of Measurement Data – Guide to the Expression of Uncertainty in Measurement”, JCGM 100:2008. [4] Knud Rasmussen, “The Influence of Environmental Conditions on the Pressure Sensitivity of Measurement Microphones”, B&K Technical Review No. 1, 2001. [5] Siegfried Hackel, Frank Härtig, Julia Hornig, Thomas Wiedenhöfer, “The Digital Calibration Certificate”, PTB-Mitteilungen 127 (2017), Heft 4, doi: 10.7795/310.20170403. [6] Digital Calibration Certificate — v2.4.0, https://www.ptb.de/dcc/v2.4.0/en. (Last accessed: 19.05.2021).
Abstract: This paper presents the ultrasonic flaw detectors calibration system at Standards and Calibration Laboratory (SCL) developed in accordance with the Group 2 tests of ISO 22232-1:2020. The calibration system contains a delay-pulse generator, a function
generator, an amplifier, an oscilloscope and a set of tunable attenuators. The measurement setup, model and uncertainty components for each tests are presented. The difference in test parameters from the preceding international standard EN 12668-1:2010
are also reviewed and compared.
References:
[1] Chuck Hellier, Handbook of Nondestructive Evaluation 3nd edition, McGraw-Hill, 2020 [2] ISO, “Non-destructive testing – Characterization and verification of ultrasonic test equipment, Part 1: Instruments,” ISO 22232-1, 2020. [3] BSI, “Non-destructive testing – Characterization and verification of ultrasonic examination equipment, Part 1: Instruments,” BS EN 12668-1, 2010. [4] Samuel C. K. Ko, Aaron Y. K. Yan and Hing-wah Li, “Calibration of Ultrasonic Flaw Detectors,” NCSLI Measure, Vol. 9, pages 62-69, 2014. [5] JCGM, “Evaluation of measurement data – Guide to the expression of uncertainty in measurement,” JCGM 100, 2008.
An Accurate RF Reference Signal for Testing Power Measuring Instruments
Blair Hall
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.4
Publisher: NCSL International | Published 2022 | Pages 14-17
Abstract: Power is a fundamental quantity in radio and microwave frequency systems, so it is important to measure it properly. Measuring instruments, such as power sensors, spectrum analysers, measurement receivers, etc, need to be calibrated using an accurately
known reference signal. Providing an accurate reference signal for such calibration work is not always easy. The output characteristics of a signal generator are difficult to measure and the cable, or network, used to connect the device under test
to a generator will also affect the power level seen at the device. If these effects cannot be accounted for properly, the accuracy of the reference level will be limited. This guide describes a simple way to produce an accurate reference signal that
uses a resistive power splitter and a pair of power sensors to improve the raw performance of a signal generator and remove the effects of an arbitrary connecting network.
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.5
Publisher: NCSL International | Published 2022 | Pages 18-22
Abstract: The information in this paper comes from some research done into the performance of thermistors calibrated at Fluke’s American Fork Primary Temperature Laboratory [1]. The laboratory does a large number of calibrations of thermistors using two
processes which will be covered later in this paper. This investigation was done to determine the feasibility of using thermistors in various processes around typical ambient temperature. It was desired that the devices under investigation remain
stable over time.
Utilizing the SI Redefinition and “NIST on a Chip” to Develop and Insert Quantum-Based, Intrinsically Accurate Technology across the Air Force, Army, and Navy
Jeremy Latsko, Rusty Kauffman, Bob Fritzsche
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.6
Publisher: NCSL International | Published 2022 | Pages 24-28
Abstract: The Air Force, Army, and Navy Metrology and Calibration program offices (henceforth, “Services”) are responsible to ensure that every measurement from a physician’s scale to those employed on end-use systems (e.g., aircraft) are accurate and traceable
to the International System of Units (SI) through the National Institute of Standards and Technology (NIST). At the core of achieving this mission is the periodic calibration of countless assets, which requires a large, global calibration chain that
must run smoothly in perpetuity. This calibration chain is like a worldwide network of interconnected airports with assets constantly arriving and departing where one hiccup might cause massive delays and the disruption of important plans (or missions).
This complex approach to ensuring accuracy and traceability has persisted for well over 100 years with only modest improvements over time. However, the 2019 SI redefinition and the “NIST on a Chip” (NOAC) program offer a path to quantum-based intrinsically
accurate technology (QB-IAT) that may be inserted further and further downstream into the calibration chain.
Measurement of Voltage Transformer Errors using a Self-Calibrating Multi-Ratio Capacitive Divider System
Frederick Emms
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.7
Publisher: NCSL International | Published 2022 | Pages 30-40
Abstract: Since 1957, the National Measurement Institute Australia (NMIA) has measured voltage transformer (VT) errors, namely voltage error (VE) and phase displacement (PD), using a self-calibrating multi-ratio capacitive divider system [1]. It utilizes
a high voltage (HV) compressed-gas capacitor in the upper arm of a voltage divider, and a range of precision air capacitors in the lower arm, some of which may be switched into the upper arm to facilitate the mathematical build-up process. The VT
errors are balanced against the capacitive divider via the use of inductive voltage dividers (IVD). This system would test VTs with primary voltages up to 100 kV and ratios from 0.1 to 1100 with a least uncertainty of 0.000 3 % for VE and 0.000 3
crad for PD. However, the equipment associated with this system occupies a large amount of space and is not portable. Over the years the demand for onsite testing has increased so there emerged a motivation to develop a new portable VT testing system.
Discovery and Rectification of an Error in High-Resistance Traceability at NPL: A Case Study in How Metrology Works
Stephen P. Giblin, Nick E. Fletcher and Colin H. Porter
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.8
Publisher: NCSL International | Published 2022 | Pages 47-55
Abstract: How are measurement errors found and remedied? This is a pertinent question for practitioners of metrology at all levels. The process of accreditation should ensure that measurement services are performed according to technically sound procedures,
and at the level of National Metrology Institutes (NMIs), intercomparisons demonstrate equivalence between laboratories. These two processes, accreditation and intercomparison, are the bedrock on which we build trust in our measurements. These systems
are not infallible though. An audit by an accrediting body may not be comprehensive enough to pick up subtle errors in a measurement procedure.
The Value of Subjective Information: An Empirical Assessment
Dr. Steven R. Dwyer
NCSLI Measure | Vol. 14 No. 2 (2022) | https://doi.org/10.51843/measure.14.2.9
Publisher: NCSL International | Published 2022 | Pages 42-46
Abstract: Metrology engineers want technically correct answers. Managers want to make decisions that trade off cost against product value. Calibration personnel want their work to count. Calibration intervals drive measurement reliability, the calibration
budget, and the value of every calibration. We affect the value of our entire calibration program when we decide how often to calibrate. Unfortunately, we don’t always have enough historical calibration results data to predict the best calibration
interval with a high degree of confidence. Although Bayesian statistical theory provides a method for including independent data sources to supplement calibration results data, limited empirical evidence exists to assess how well Bayesian statistics
predicts measurement reliability. The literature has no example that measures how well subjective information estimates measurement reliability. This paper attempts to fill that gap.
