Analysis of calibration errors of a standard capacitance comparator

Translated from Izmeritel'naya Tekhnika, No. 4, pp. 49–51, April, 1990.     

Uncertainties in calibration using capacitance diaphragm gauges as reference standard

A study of the uncertainties in calibration using capacitance diaphragm gauges as reference standard in the range from 1000 mbar to 10⁻³ mbar is presented. The contributions to the expanded uncertainty are: (i) Uncertainty from the calibration certify of the reference standard; (ii) Long-term stability or shift; (iii) Uncertainties inherent to the reference standard; (iv) Uncertainties derived from the calibration chamber; and (v) Uncertainties derived from the calibration procedure. These contributions have been determined for four reference standard capacitance diaphragm gauges of 1.3 mbar, 13 mbar, 130 mbar and 1300 mbar full scale used in routine calibration. Long-term stability or shift jointly with the uncertainty displayed in the calibration certifies issued by a National Metrological Laboratory are the main contributions to the expanded uncertainty. Values of the shift for each of the reference standard for a period of several years are presented and discussed. Best-expanded uncertainties obtained from calibration of a gauge of similar characteristics to the reference standards are:

10−3-1 mbar	4-0.2% of the reading
1-13 mbar	0.2% of the reading
13-130 mbar	0.2-0.08% of the reading
130-1300 mbar	0.2-0.06% of the reading

Full-size table

     

Watt and voltampere transfer standard

A new instrument which will be used as a transfer device between the national watt and VA standards of the National Research Council of Canada and the standards maintained by Canadian electrical utilities and electricity meter manufacturers is described. The relative error of this instrument is less than 50 ppm for power or energy and 100 PPM for voltampere measurements. The stability of the instrument during a field test cycle of about two weeks was on the order of 20 ppm. A dedicated pulse-frequency counter and a stable phantom power source were supplied to utilities to achieve high-accuracy on-site measurements     

A high frequency stray-immune capacitance transducer based on thecharge transfer principle

A stray-immune capacitance measuring instrument based on the charge transfer principle is described. It has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip. The effects of stray capacitances, including those of the switching components, have been eliminated by using a special switching arrangement, resulting in a baseline drift of 0.02 pF (at 1-MHz measurement frequency) over a 12-h period     

毫瓦级超声功率传递标准的研制

针对各类毫瓦级超声功率计的量值溯源问题,选用压电陶瓷材料,根据其压电效应原理,设计为厚度伸缩振动模式,采用能陷技术及真空镀膜等技术工艺,制作了一系列1MHz、3MHz、5MHz的园片形单元超声换能器,并研制与之配套的阻抗匹配器,与功率信号源等,组成一套毫瓦级超声功率传递标准。该套标准经济实用、性能可靠稳定,重复性好,有效地解决了毫瓦级超声功率计的量值溯源问题。     

Calibration of a low-voltage AC-DC transfer standard

The paper describes improvements in the determination of the ac-dc transfer difference of an electronic low-voltage transfer standard (LVTS). Expanded calibration uncertainty in the 10 Hz-1 MHz frequency range and 2 mV-100 mV voltage range has been estimated to be less than 100 μV/V. Improvements have been achieved by modification of the step-down procedure that does not require loading error corrections and careful examination of the error sources     

Tests on the IEN electrometric AC-DC transfer standard

Tests on the electrometric AC-DC transfer standard built at IEN have been performed. The instrument was shown to work correctly, and comparison with thermal converters showed a short-term repeatability (1σ) of about 2 parts in 10⁶. Mechanical effects such as deformations and vibrations have been analyzed, both theoretically and experimentally. Direct determinations of the transfer difference made using thermal converters have shown results almost comparable with those obtained by the step-up procedure. The long-term stability of the instrument has also been investigated     

10MN叠加式力标准机的研制

简述10MN叠加式力标准机的工作原理,通过对横梁、加载系统、液压系统、控制系统以及测试系统进行创新设计,并采用新的力值加载结构和满足称重传感器、标准测力仪的测试系统,成功研制高精度10MN叠加式力标准机。该10MN叠加式力标准机示值重复性不大于0．02％,力值误差在±O．05％内,相对扩展不确定度优于0．1％（k=2）。     

Both active and reactive power and energy transfer standard

A thermal converter to DC voltage, with 10-ppm accuracy and a frequency range of 0-200 kHz, which can be used for active power measurements, has been developed using an infrared thermal converter. Moreover, a proposal for implementing, with lower accuracy, the converter for energy and reactive power is also illustrated     

Evaluation of ADC testing systems using ADC transfer standard

A transportable high-stability reference AD device was designed and built to compare the systems for testing the dynamic quality of analog-to-digital converters (ADCs) or analog-to-digital (AD) modules. Three different input modules can be used in the frequency range up to 5 MHz. First, this paper refers to the results of an AD device application in the frequency range of the testing signal up to 100 kHz, where four ADC testing systems were compared in different laboratories, and a short time amplitude and/or frequency instability of testing signal generators was evaluated. Second, it describes the first experience of its application in the frequency range from 100-5 MHz.     

Traceability of the 10-kΩ standard at IEN

The traditional scaling method used at the Istituto Elettrotecnico Nazionale (IEN) for the calibration of the 10-kΩ standard is compared with more straightforward techniques: one based on the linearity of a DVM and the other on a commercial current comparator bridge. For the three methods, the measurement results and the uncertainty budgets are reported. The agreement is better than 1×10^-7     

742A-1及742A-10k型传递标准电阻值测量结果不确定度的评定

742A标准电阻是供精密电阻校准使用的高准确度工作标准。随标准电阻提供校准修正数据表,表中的修正值以0.5℃的温度间隔给出,其优异的温度稳定性使之可以工作在18~28℃的温度范围之内。742A小巧坚固、使用方便,大大减小因温度和机械振动而导致的电阻变化。根据QJ55宽量程直流比较仪式电桥的测量原理,采用直接比较法,用一等标准电阻器和QJ55型直流电流比较仪式电桥,对742A标准电阻进行检测,对测量结果的不确定度评定,分析测量过程中不确定度的来源,并量化分析,得到合成标准不确定度和扩展不确定度。     

Development of a new transfer standard for high UV irradiances

Source-based radiometry requires reliable transfer standards which are easy to handle. For low irradiances in the UV spectral range, 30 W deuterium lamps are commonly used. However, for the growing field of high UV irradiance applications, new high power standards are required. Here we report on a Xe-Hg lamp system which has been characterised and improved to match the high requirements of a working standard. For this purpose, several parameters of the system such as lamp stability, re-ignition reproducibility, irradiance uniformity and usability have been investigated. Components for the customised light guide-based output optics have been selected with the help of extensive characterisations. The resulting lamp system can be used for a high-grade instrument calibration at high UV irradiance levels.     

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%.     

电容传感器新型电容测量电路设计

提出了一种基于V／T变换的用于电容传感器的电容测量电路。它将被测微小电容变化量转换成时间信号并由单片机进行处理，电路结构简单，电路中没有影响测量稳定性和产生零点漂移的元器件，大幅度地降低了测量过程中的噪声。     

Two capacitance dilatometers

Two different dilatometric devices designed for magneto-strictive strain measurements at low temperatures are described. Their sensitivity is of the order of 10^?10 for relative length changes. They are provided with an adjustable gap system which makes it possible to change the gap between the capacitor plates at helium temperature.     

A calorimeter for μW level optical power transfer standard

A calorimeter which can measure microwatt-level optical power has been developed for an optical power transfer standard. It can measure the optical power of a light beam and can be used with optical fiber simply by attaching an adapter. This calorimeter sensor uses a compensative absorber to reduce the influence of pressure fluctuation and temperature variation in the measurement room and an ultra-low-noise preamplifier. With this calorimeter, the standard deviation of the measured value is in the range of 0.02-0.4% in 20-mW to 10-μW optical power measurements. An error evaluation for an optical power level of 10 μW yielded a two-sigma (two standard deviation) total uncertainty of 0.9%     

Towards accurate measurement of the frequency dependence of capacitance and resistance standards up to 10 MHz

Progress toward an understanding of the frequency dependence of capacitance and resistance standards at frequencies up to 10 MHz is presented. A qualitative comparison is also made for capacitance and dissipation factor measurements between the National Physical Laboratory (NPL) high-frequency four terminal-pair (4TP) bridge and a commercial impedance analyzer for the first time. A set of novel high-frequency calculable coaxial resistance standards, of nominal 100 /spl Omega/ and 1 k/spl Omega/ values, have been developed and their calculated frequency dependence up to 1 MHz is given.