Standardisation of pressure measurement using pressure balance as transfer standard

This paper describes the results of the interlaboratory comparison for pressure measurements of 9 laboratories that are accredited by the National Accreditation Board for Testing and Calibration of Laboratories (NABL). The artifact used for the comparison was a pressure balance covering the pressure range (7 to 70) MPa. The primary objective of this comparison was to assess the laboratory’s technical competence to perform measurements and also to assess the compatibility of the results submitted by the laboratories. The comparison began during March 2008 and ended during April 2010. For assigning the reference values, the pilot laboratory (NPLI) carried out 3 calibrations of the transfer standard; the first one at the beginning, the second at the middle and the last one at the end of the programme. The comparison was carried out at 10 pressure points i.e. (7, 10, 15, 20, 25, 30, 40, 50, 60 and 70) MPa throughout the entire pressure range of (7 to 70) MPa. The measurements were carried out by each laboratory with their own resources (personnel, calibration systems, environmental conditions in their installations). The deviations for each laboratory were compared against the reference values and the compatibility of the results was calculated using the normalized error value method. Out of the total 87 measurement results reported, 68 (78.2%) results are found in good agreement with the results of the reference laboratory. The normalized error (E_n) values of 5 laboratories out of the total 9 were found well within ± 1 over the entire pressure range. However, 2 other laboratories had shown good agreement with the reference values except one pressure point each. The E_n values of one of the participating laboratory were found beyond acceptable limits at all measurements points. Another laboratory had acceptable results only at 3 pressure points. The laboratories with unacceptable results have been advised to review their pressure measurement process. The deviations between laboratory values and of the reference values were found well within the uncertainty band of the reference values for 37% measurement results. The relative deviations for 82 measurement results were found well within 0.05%.     

Comparison of Meteorological Service Calibration Laboratories in Southeastern Europe

Interlaboratory comparisons serve as tools for assessment of measurement results performed by calibration laboratories in the relevant field of measurement. They are effective means to demonstrate technical competence of the participant and are used as a technical base for accreditation. However, in the network of meteorological services calibration laboratories, comparisons among laboratories are still rare. Some laboratories are still not evaluating measurement uncertainty, thus causing problems when comparing meteorological data from different countries. The Environmental Agency of the Republic of Slovenia (EARS), serving in the frame of the World Meteorological Organization as a Regional Instrument Centre, has organized a round-robin comparison of calibration laboratories of meteorological services in the southeastern part of Europe using instruments for temperature, relative humidity, and barometric pressure. Each participant laboratory had to calibrate a set of instruments at defined calibration points, to evaluate the measurement uncertainty (if possible), and to report the results. EARS RIC invited the National Hydrometeorological Services in the southeastern part of Europe to take part in the intercomparison. In addition, the Laboratory of Metrology and Quality (MIRS/UL-FE/LMK), which holds the Slovenian national standard for temperature and relative humidity, was also invited to participate in the comparison and in the data analysis. Results from MIRS/UL-FE/LMK and EARS were used to calculate the temperature and humidity comparison reference values, while the EARS results were taken as reference values for barometric pressure.     

Validation of RF power standard in the frequency range of 100 MHz to 18 GHz by an inter laboratory data comparison

Radio frequency (RF) power is one of the most important quantities in RF metrology. An inter laboratory data comparison of RF power for the validation of a coaxial microcalorimeter has been carried out between Physikalisch-Technische Bundesanstalt (PTB-Germany) and National Physical Laboratory India (NPLI). A coaxial thermistor mount equipped with type N connector is used for this intercomparison. The results show good agreement in measuring the effective efficiency of the coaxial thermistor mount between the two laboratories within their claimed expanded uncertainty. It confirms the equivalence of national standards for RF power in the frequency range of 100 MHz to 18 GHz.     

高压环道气体流量标准装置

介绍了中国计量科学研究院2014年建成的高压环道气体流量装置,并对其不确定度进行了分析。高压环道气体流量工作标准装置采用4台涡轮流量计作为标准表,具备2.5MPa、1600m3/h的测量能力。涡轮流量计标准表使用原位校准及“绝压+差压”的压力测量方式。装置的扩展不确定度为0.21%(k=2)。     

Assigning RF/DC Transfer Difference to High Frequency Voltage Primary Standard up to 1 GHz at NPLI

National Physical Laboratory (NPLI) India is the premier research and development center and the National Metrology Institute, which provides traceability in measurements by calibration throughout the country. High frequency (HF) voltage is one of the important parameter in electrical metrology. At NPLI the primary standard of HF voltage at frequencies from 1 to 1,000 MHz is a twin resistance coaxial power mount. The calibration technique and establishing the traceability by assigning the RF/DC transfer difference to HF voltage primary standard are described in this paper. The HF voltage primary standard has been characterized by assigning RF/DC transfer differences to it in terms of effective efficiency, RF impedance and DC resistance. The calibration results of the primary standard have been discussed in this paper. The assigned RF/DC transfer difference (δ) and the expanded uncertainty of HF voltage primary standard at 1.0 GHz is (?5.2 ± 5.4) mV/V.     

微风速标准装置的建立和热线风速仪校准方法的实验研究

中国计量科学研究院建立了微风速标准装置,基于该标准装置对热线风速仪的校准展开了实验研究。微风速标准装置基于相对法测量原理,实验通过气浮滑车搭载热线风速仪运动,由激光干涉仪测得的距离对时间微分得到标准速度,通过这种方式实现了热线风速仪的校准。滑车的运动速度可以溯源到国家计量院的时间和长度基准;此外,根据热线风速仪传感器的理论模型计算得到了热线风速仪的静态特性方程,比较理论模型与校准结果,发现二者具有良好的一致性。实验结果和不确定度分析表明:微风速标准装置的扩展不确定度U=0.82%（k=2）;热线风速仪校准结果的扩展不确定度U=2.42%（k=2）。     

A novel multiple reflections technique to calibrate polygons and evaluation of its uncertainty of measurement

In the field of angle metrology, angle gauges and polygons are the material artefact standards. Conventionally, autocollimator along with indexing table, are used for the calibration of angle gauges and polygons. A novel multiple reflections method is devised at NPLI to improve the uncertainty of measurements during calibrations. A polygon under calibration is fixed at the centre of a Moore’s indexing table within eccentricity offset ± 20μm. A reference autocollimator is aligned to one of the face of the polygon. A flat reflector is fixed in the centre of a rotatable table. The rotatable table is arranged to collect the optical beam on to the flat reflector then deflected to same face of the polygon, wherefrom the light beam is received at the autocollimator. Thus the optical beam strikes the same face of the polygon twice. Therefore the resolution of the reference autocollimator is virtually doubled. In this experimental setup, two set of readings are obtained simultaneously. One set of the readings corresponds to conventional method and the second set of the readings belongs to the proposed novel method. The readings of the autocollimator are analysed and the results are discussed in the article. The results thus obtained by conventional method are compared with the results obtained using the proposed method. Using this novel calibration method, the uncertainty of measurement is improved from ± 0.39″ to ± 0.23″.     

Coordinate-Based Evaluation of Two Dimensional Artefact Calibration Value as the Reference Standards for Coordinate Measuring Machines

Two dimensional standards are important materials which are used in the calibration and the verification of coordinate measuring machines. In several countries, the national metrology institutes or accredit laboratories provide the calibration services of the two dimensional standards such as ball plates, hole plates and grid plates. The metrological equivalence of the measurement standards among the calibration providers is validated through the key comparison program. In the previous key comparison for a ball plate and a hole plate, the equivalences among the participants’ calibration results were verified on the distances between the No. 1 ball/hole (i.e., the origins of the workpiece coordinates) and other balls/holes on the plates respectively. The essential measurands of the two dimensional standards are the coordinates of the feature points, however, the measurement equivalences on them have not been verified. In this study, the authors propose the coordinates-based evaluation of the reference values and their uncertainty in two dimensional standard calibration comparison.     

Static expansion primary vacuum standard — Part 1: Determination of the volume ratio of the expansion stage

Measurement of volume ratio forms an essential part of the characterization of a static expansion system (SES) for the generation of pressures in the medium and high vacuum region. Because of the complexity of the vacuum chambers, it is not possible to determine the absolute volumes of the chambers involved. Hence an expansion process is resorted to, in which the gas enclosed in the small volume at a known pressure is allowed to expand, under isothermal conditions, into the large volume. The accuracy of the volume ratio thus determined depends on the stability of the vacuum gauges used for the measurement of initial and the final pressures and the ambient temperature. High accuracy resonant silicon gauges (RSGs) of two different ranges, one 130 kPa full scale and the other 1 kPa full scale for measurement of the initial and final pressures are found to be useful. This paper reports the results obtained with these RSGs for the measurement of the volume ratio of the National Physical Laboratory, India (NPLI) SES which is nominally 2820. With the use of the RSGs, and calibrated platinum resistance thermometers (PRTs) mounted inside the vacuum chambers, it has been possible to measure the volume ratio within the relative expanded uncertainty (k = 2) of 0.0014. The results of the volume ratio determination exercise are given in this paper while the Part 2 of this paper will discuss the procedure for the calibration of spinning rotor gauges on the Static expansion primary standard.     

荧光量子效率绝对法测量系统校准及不确定度评定

荧光量子效率是发射与吸收的光子数之比,是表征荧光材料发光性能的关键参数。然而,用于绝对法测量荧光量子效率的光路和探测器未经校准溯源或是校准方法不当,会造成测量光谱的不准确,进一步影响荧光量子效率计算结果的不准确。采用汞氩灯对单色仪进行校准,保证了激发波长和发射波长的准确性,利用标准辐射源对光路、发射单元单色仪和探测器进行光谱相对强度校准,保证了激发波段和发射波段光谱相对强度的准确性;最后从测量模型出发,对测量不确定度进行了分析,得到在300~360nm的激发光波段和370~900nm的发射光波段内相对合成标准不确定度为3.58%,相对扩展不确定度为7.16%,k=2。通过对单色仪波长校准以及对光谱相对强度进行校准,为荧光量子效率的准确测量提供了参考。     

A Nickel–Carbon Eutectic Cell for Contact and Non-contact Thermometry

The highest-temperature, defining fixed point of the International Temperature Scale of 1990 (ITS-90) is the copper freezing point (1,084.62°C). Many international metrology institutes are investigating the use of transition temperatures of metal–carbon alloys as references for the calibration of temperature measuring instruments above the copper point, making it possible to reduce the calibration uncertainty of pyrometers in radiation thermometry and thermocouples in contact thermometry. This research is being performed mainly by radiation thermometry laboratories that have developed specific cells with blackbody cavities containing relatively small quantities of metal–carbon alloys. Parallel to this, some laboratories have also developed cells with these same alloys, but of a different design, suitable for the calibration of thermocouples. This report concerns the development of a nickel–carbon eutectic cell (≅1,329°C) at Inmetro, with which either a radiation thermometer or thermocouple can be calibrated. The measurements of the temperature of this cell were performed using the reference radiation thermometer of the Pyrometry Laboratory and Pt/Pd thermocouples that were constructed, stabilized, and calibrated at the Thermometry Laboratory. Details of the cell fabrication, as well as the instrumentation used for the measurements are given. The results of a comparison between the two different types of measurement are reported, including the uncertainty budgets of both methods.     

Improving the Traceability of Meteorological Measurements at Automatic Weather Stations in Thailand

A joint project between the National Institute of Metrology Thailand (NIMT) and the Thai Meteorology Department (TMD) was established for improving the traceability of meteorology measurements at automatic weather stations (AWSs) in Thailand. The project aimed to improve traceability of air temperature, relative humidity and atmospheric pressure by implementing on-site calibration facilities and developing of new calibration procedures. First, new portable calibration facilities for air temperature, humidity and pressure were set up as working standard of the TMD. A portable humidity calibrator was applied as a uniform and stable source for calibration of thermo-hygrometers. A dew-point hygrometer was employed as reference hygrometer and a platinum resistance thermometer (PRT) traceable to NIMT was used as reference thermometer. The uniformity and stability in both temperature and relative humidity were characterized at NIMT. A transportable pressure calibrator was used for calibration of air pressure sensor. The estimate overall uncertainty of the calibration setup is 0.2 K for air temperature, 1.0 % for relative humidity and 0.2 hPa for atmospheric pressure, respectively. Second, on-site calibration procedures were developed and four AWSs in the central part and the northern of Thailand were chosen as pilot stations for on-site calibration using the new calibration setups and developed calibration procedures. At each station, the calibration was done at the minimum temperature, average temperature and maximum temperature of the year, for air temperature, 20 %, 55 % and 90 % for relative humidity at the average air temperature of that station and at a one-year statistics pressure range for atmospheric pressure at ambient temperature. Additional in-field uncertainty contributions such as the temperature dependence on relative humidity measurement were evaluated and included in the overall uncertainty budget. Preliminary calibration results showed that using a separate PRT probe at these AWSs would be recommended for improving the accuracy of air temperature measurement. In case of relative humidity measurement, the data logger software is needed to be upgraded for achieving higher accuracy of less than 3 %. For atmospheric pressure measurement, a higher accuracy barometer traceable to NIMT could be used to reduce the calibration uncertainty to below 0.2 hPa.     

一种纯水机内置在线监测仪表的现场校准方法

为满足实验室纯水机内置在线监测仪表的现场校准需求,建立了一套由高精度电导率仪、总有机碳分析仪和可调流速缓冲装置组成的标准测量装置。通过将纯水机在线监测仪表的测量结果与标准测量装置的测量结果进行比较,实现了纯水机在线电导率/电阻率和总有机碳监测仪表的现场校准。对11家实验室纯水机进行现场试验和分析。结果表明:纯水机在线电导率仪器相对示值误差在-2.4%～15%,测量扩展不确定度为1.7%(k=2);总有机碳仪器相对示值误差为-98%～125%,测量扩展不确定度为4.8%(k=2)。     

Introduction of the guide to theExpression of Uncertainty in Measurement in Russia

It is shown that the differences between the concept of measurement uncertainty and traditional error theory are mainly terminological. Thus, introduction of the Guide to the Expression of Uncertainty in Measurement does not involve a transition to new methods of measurement-accuracy evaluation or a total revision of the archive of metrological reference documents. It will be sufficient to make the transition to the language of uncertainty in compiling verification and calibration certificates and measurement reports. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 31–32, May, 2000.     

Preparation and Certification of Novel Reference Material for Smoke Density Measurements

A novel type of reference material has been prepared and characterized for smoke density chamber calibration in the flame condition by Fire Protection Laboratory, National Institute of Standards, Egypt. The new reference material was fabricated by mixing modified magnesium hydroxide nanoparticles (MH-NP-OP) with acrylonitrile–butadiene–styrene copolymer (ABS). The reference material was certified for the physical properties of maximum specific optical density (D_m) and corrected maximum specific optical density (D_m·corr) using the analysis of two different competent laboratories. Preparation, characterization, homogeneity testing and certified value assignment for the developed reference material have been studied. It was clearly demonstrated that the smoke measurement of the two laboratories are harmonic which is an obvious prerequisite for the confidence assessment of the reference material. A metrological approach was followed to detect the statistical biases between different laboratories data to achieve an appropriate accuracy in smoke measurements. The obtained measurement results were statistically analyzed and the certified values of D_m and D_m·corr for reference material were estimated as 510.35 and 472.95, respectively as well as their expanded relative uncertainties at confidence level 95% were recorded 2.78 and 2.7%, respectively. The developed reference material are expected to be used to assist in validating smoke measurements of different materials to realize their fire hazard when be used in building.     

用锌凝固点和水沸点检定二等标准铂电阻温度计的扩展不确定度评定

按时规范,ＪＪＦ１０５９－１９９９,对二等标准铂电阻温度计在锌凝固点及水沸点检定的不确定度进行了评定,通过建立测量数学模型确定各标准各不确定度分量,并按不确定度传播公式给出固定点间各温度点的扩展不确定度及包含因子。     

变温变压环境中大面积水听器灵敏度低频校准方法

针对在变温变压环境中缺少低频大面积水听器灵敏度校准手段的问题,提出了在行波管中校准水听器的半行波管法:将待校准水听器放置于行波管中,通过控制行波管两边的有源终端,在待校准水听器与辅助换能器之间形成行波场,与主发射换能器之间形成驻波场。推导了水听器灵敏度的校准公式。在常温常压环境下,通过与传统低频校准方法的比对,校准结果具有良好的一致性,证明该方法可以有效校准大面积水听器的灵敏度;在不同温度与压力环境下对水听器灵敏度的校准结果,说明了该方法在变温变压条件下校准水听器的可行性,为大面积水听器灵敏度的校准提供了一种方法;对该方法进行了测量不确定度评定,其扩展测量不确定度为3dB。     

毛细管黏度计校准能力验证

针对毛细管黏度计校准在能力验证中存在的问题,详细分析了校准过程中的影响因素,给出了测量不确定度来源及不确定度评定,有助于提高相关实验室黏度计校准结果的准确度。     

Report of the Proficiency Testing in the Pneumatic Pressure Region up to 5 MPa

We report the performance of calibration laboratories in the pneumatic pressure region (0 to 5) MPa through a recently conducted inter-laboratory comparison. Six NABL (National Accreditation Board for Testing and Calibration Laboratories) accredited laboratories participated in the program. The proficiency testing program was organized and piloted by CSIR-National Physical Laboratory. The program started in June 2010 and was completed in October 2011. The artifact used was a high precision pressure dial gauge. The reference values were generated by the pilot laboratory. The deviations for each participating laboratory were estimated against the reference pressure values and the compatibility of the results was calculated using the conventional method. Out of the total measurements made, all but two were found to be in good agreement with the reference values. The normalized error values (E _n) of five laboratories out of the total six were found well within ± 1 over the entire pressure range.