Standards And Calibration Laboratory Research Articles

Force sensitivity calibration of artificial mastoids

The Standards and Calibration Laboratory (SCL) has set up a system for calibration of artificial mastoids to meet the growing demand for calibration of bone-conduction hearing aids and audiometers in the audiology industry of Hong Kong. An artificial mastoid (or mechanical coupler, as specified in IEC 60318-6) is a device that mimics the mechanical characteristics of the human mastoid (one of the bones of the skull behind the ear). It is basically composed of a dome-shaped structure and a force transducer. This paper mainly illustrates the method for measuring the force sensitivity level (in unit of dB re 1 pC/N) of an artificial mastoid in the frequency range of 125 Hz to 8 kHz. The calibration system has been automated to meet the demand for artificial mastoid calibration services in Hong Kong. This paper describes (i) the method of determining the force sensitivity level of an artificial mastoid, (ii) the measurement model and uncertainty evaluation, and (iii) the measurement results and details of the calibration system.

Implementation of instantaneous comparison methods in temperature gradient evaluation of stirred liquid temperature baths

Temperature gradient is an important performance indicator of a stirred liquid bath. Its evaluation requires measuring the temperature differences between different bath positions. A common way to do that is to place two SPRTs at two positions and measure their resistances against a standard resistor (R SPRT1/R S and R SPRT2/R S) sequentially (the sequential method). A drawback of this method is the existence of a time gap between the two measurements rendering the results susceptible to temporal temperature variation. The instantaneous comparisons method offers a better solution by measuring the resistance ratio of two SPRTs directly (R SPRT1/R SPRT2) and deriving their temperature difference at the same moment eliminating the time gap. To implement this method at the Standards and Calibration Laboratory (SCL) of Hong Kong, the resistance ratio of SPRT1 to a standard resistor (R SPRT1/R s) is firstly measured to determine the initial bath temperature. After that, the resistance ratios of SPRT1 to SPRT2 (R SPRT1/R SPRT2) are measured with the two SPRTs placed at different positions and immersion depths in the bath. This paper describes the derivation of the temperature difference from the SPRT resistance ratio using the ITS-90 reference equations and the estimation of the measurement uncertainties. The potential of reducing the uncertainties of measured temperature gradient by leveraging the correlation of the two SPRTs calibrated at the same set of temperature fixed points is discussed. The paper also compares the calibration results obtained by the instantaneous comparisons method and the sequential method.

Calibration of Loop Antennas in Accordance with CISPR 16-1-6:2014+AMD1:2017 at SCL

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.

Implementing a Thin-Film Reflectance Model for Trap Detectors at the SCL

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.

Pressure Calibration of Quarter-Inch Working Standard Microphones by Comparison

The Standards and Calibration Laboratory (SCL) in Hong Kong has developed a system for calibration of quar-ter-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.

Calibration of Ultrasonic Flaw Detectors in Accordance with ISO 22232-1:2020

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.

Calibration of Line Impedance Stabilization Networks / Artificial Mains Networks in Accordance with CISPR 16-1-2 Ed 2.1 2017-11

This paper describes a measurement procedure developed by the Standards and Calibration Laboratory (SCL) for measuring the parameters of single phase 50 Ω//(50 μH + 5 Ω) V-network type line impedance stabilization networks (LISN) or artificial mains networks (AMN) specified in the international standard CISPR 16-1-2, which are the impedance at the equipment-under-test (EUT) port, the isolation between the power port and the receiver port, and the voltage division factor between the EUT port and the receiver port. The corresponding measurement models and evaluation of measurement uncertainties are presented. The characterization method of in-house developed adapters for BS1363 type plug and socket is also presented.

Calibration of Timing Parameters of Still Image Cameras and Video Cameras by a Two Dimensional LED Array

This paper presents a t wo-dimensional 10 x 10 LED array system developed in-house at t he Standards and Calibration Laboratory (SCL) for the calibration of timing parameters of still image cameras and video cameras. In this paper, the circuit design and the calibration methods for cameras of different shutter types (rolling shutter or global shutter) are presented. This LED array may also be used to verify the shutter type of cameras. The frequency of the clock signal applied in the calibration is traceable to the SI through the cesium beam frequency standard maintained at SCL.

Computer Aided Verification of Voltage Dips and Short Interruption Generators for Electromagnetic Compatibility Immunity Test in Accordance with IEC 61000-4-11: 2004 + AMD: 2017

This paper describes a procedure and a computer-aided system developed by the Standards and Calibration Laboratory (SCL) for verification of voltage dip and short interruption generators in accordance with the international standard IEC 61000-4-11:2004+AMD1:2017. The verification is done by calibrating the specified parameters and comparing with the requirements stated in the standard. The parameters that should be calibrated are the ratios of the residual voltages to the rated voltage, the accuracy of the phase angle at switching, and the rise time, fall time, overshoot and undershoot of the switching waveform. A specially built adapter is used to convert the high voltage output waveforms of the generators to lower level signals to be acquired by a digital oscilloscope. The other circuits required for the testing are also provided. In addition, the paper discusses the uncertainty evaluations for the measured parameters.

Full Issue Download Vol. 13 No. 1 2021 The Importance of the Measurement Infrastructure in Economic Recovery from the COVID-19 Pandemic Richard J. C. Brown , Fiona Auty, Eugenio Renedo, Mike King NCSLI Measure | Vol. 13 No. 1 (2021) | doi.org/10.51843/measure.13.1.1 Publisher NCSL International | Published February 2021 | Pages 18-21 Abstract: This paper describes the many, evidenced-based benefits

Facilitating the uptake of established methodologies for risk-based decision-making in product conformity assessment taking into account measurement uncertainty by providing dedicated software is the aim of the European project EMPIR CASoft(2018–2020), involving the National Measurement Institutes from France, Sweden and the UK, and industrial partner Trescal (FR) as primary supporter. The freely available software helps end-users perform the required risk calculations in accordance with current practice and regulations and extends that current practice to include bivariate cases. The software is also aimed at supporting testing and calibration laboratories in the application of the latest version of the ISO/IEC 17025:2017 standard, which requires that“…the laboratory shall document the decision rule employed, taking into account the level of risk […] associated with the decision rule and apply the decision rule.” Initial experiences following launch of the new software in Spring 2020 are reported.

Developing an Integrated Approach for the Performance Verification for Large Coordinate Measuring Machines (CMM) at the Standards and Calibration Laboratory (SCL)

To support local industries, the Standards and Calibration Laboratory (SCL) in Hong Kong has developed a performance verification service for Coordinate Measuring Machines (CMM) meeting the require...

Calibration of the Frame Rate of High-Speed Digital Video Recorders by Stationary Counting Method: Application of the Stroboscopic Effect

AbstractBy leveraging the stroboscopic effect, a new method, namely the Stationary Counting Method, has been developed at the Standards and Calibration Laboratory (SCL) of Hong Kong for calibrating...

Calibration of Optical Fiber Time Domain Reflectometers in Accordance with IEC 61746-1:2009

This article describes the calibration system developed by the Standards and Calibration Laboratory (SCL) for calibrating single mode optical time domain reflectometers (OTDR) fitted with FC connec...

Calibration of Electrocardiograph (ECG) Simulators

The Standards and Calibration Laboratory (SCL) in Hong Kong has set up a calibration facility for electrocardiograph (ECG) simulators. ECGs are medical devices designed to measure the electrical si...

A Multi-Purpose, Detector-Based Photometric Calibration System for Luminous Intensity, Illuminance and Luminance

A multi-purpose detector based calibration system for luminous intensity, illuminance and luminance has been developed at the Government of the Hong Kong Special Administrative Region, Standards and Calibration Laboratory (SCL). In this paper, the measurement system and methods are described. The measurement models and contributory uncertainties were validated using the Guide to the Expression of Uncertainty in Measurement (GUM) framework and Supplement 1 to the GUM – Propagation of distributions using a Monte Carlo method in accordance with the JCGM 100:2008 and JCGM 101:2008 at the intended precision level.

Calibration of Defibrillator Analyzers

Abstract:The Standards and Calibration Laboratory (SCL) in Hong Kong has set up a calibration facility for defibrillators and defibrillator analyzers. Defibrillators are medical devices designed to resume the normal heart pulse of a patient by discharging energy pulses to a person who is suffering from an emergency cardiac attack. They are commonly used in hospitals and medical institutes. At the SCL, the energy delivered by a defibrillator is measured using a high quality digital sampling system. The system includes a high voltage divider, a sampling voltmeter, an impedance analyzer, and a control computer. The sampled voltage waveform is digitally processed to derive the delivered energy. The system can also be used to check the accuracy of a defibrillator analyzer. The sampling system and its signal processing are described in this paper. To ensure the accuracy of the sampling system, it is calibrated against the laboratory's voltage and time reference standards. A standard waveform with calculable ene...

Calibration of Optical Fiber Laser Sources

Abstract:A calibration system for optical fiber laser sources has been developed at the Government of the Hong Kong Special Administrative Region Standards and Calibration Laboratory (SCL). The measurements of wavelength, output power level and output power stability of optical fiber laser sources fitted with fiber channel/angled physical contact (FC/APC) connectors are detailed. The wavelength is directly measured by the laboratory wavelength meter. The standard measurement uncertainty obtainable by this calibration method is less than 1 picometer (pm). The output power is the summation of the measured power by the laboratory's electrically calibrated pyroelectric radiometer (ECPR), and the insertion loss between the source and the ECPR with a standard measurement uncertainty of about 3.7 %. The output power stability is evaluated by measuring the maximum and minimum fluctuation of the measured optical power using the laboratory ECPR which has three significant digits of resolution.

Calibration of Ultrasonic Flaw Detectors

Abstract:A calibration system for ultrasonic flaw detectors has been developed at the Government of the Hong Kong Special Administrative Region Standards and Calibration Laboratory (SCL) in accordance with the international standard EN12668-1:2010. The calibration covers all the periodic and repair tests (the Group 2 tests) required in the standard for checking the performance of ultrasonic instruments, including their stability, transmitter pulse parameters, receiver response parameters, and time-base linearity. During the calibration, the ultrasonic flaw detector's transmitter is connected to a combination of a delay generator and function generator which simulates a delayed version of the transmitted signal as the reflected signal. The simulated reflected signal is then fed to the receiver of the ultrasonic flaw detector. The stabilities over time and voltage variation of the received waves are measured and the receiver frequency response is obtained. Other performance parameters of the receiver such a...

Final report on APMP.M.H-S3: Comparison on hardness measurement Rockwell scale A and B

The APMP.M.H-S3 Rockwell hardness intercomparison was initiated by NIMT, Thailand and the required protocol was prepared by NIMT and checked by Dr John Man, MNIA, Australia, in 2009. PTB, Germany, Standards and Calibration Laboratory (SCL), Hong Kong, National Physical Laboratory (NPLI), India, and Korea Research Institute of Standards and Science (KRISS), Korea, participated in this comparison.This comparison exercise was focused on the measurement range of 25 to 100 HRBW scale and 35 to 85 HRA scale. The round robin test was done during the period from April 2010 to October 2010. The participating laboratories have demonstrated the capability of the machine and the operating conditions according to ISO 6508 Part 3 to perform the measurements. However, SCL, Hong Kong, could demonstrate their capability to perform the measurements only according to ISO 6508 Part 2.The CMCs declared by the different laboratories lie in the range of 0.30 HRA to 0.40 HRA and 0.40 HRBW to 0.75 HRBW. The CMC declared by SCL for the Rockwell B scale is 1.5 HRBW for the reason described above. It is observed from the results that the measurement uncertainty is estimated not less than the CMCs declared by the laboratories.From the measurement results provided by all the participating laboratories, the En ratio was determined to establish the degrees of equivalence. The En ratio was calculated by including as well as by excluding the results of the laboratory which has performed the test according to ISO 6508 Part 2 in order to make sure that it does not affect the overall results. It is noticed that the En ratio was still found to remain less than 1.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Calibration of Stopwatches by Utilizing High Speed Video Recordings and a Synchronous Counter

Abstract:A new method for the calibration of stopwatches, called video totalize method, has been developed at the Hong Kong Standards and Calibration Laboratory (SCL). The method starts with the taking of two short video clips of the display of the stopwatch under test, together with the reading of an in-house designed synchronous counter, with the two clips separated by an interval of six to seven hours. The 10-digit synchronous counter is driven by a 1 kHz clock which is phase locked to the cesium frequency standard of SCL. The elapsed times measured by the stopwatch and the synchronous counter are obtained by viewing the recorded video to search frame-by-frame for the instant at which the reading of the stopwatch changes. Using this method, the measurement uncertainty is no longer constrained by the display resolution of the stopwatch, but instead is limited only by the frame rate of the video recording. Digital cameras that can record video at 420 frames per second with usable image quality are commer...