Primary Power Standard Research Articles

Identification of RF&MW Microcalorimeter Weak Points by Means of Uncertainty Analysis

Microcalorimeters are used by National Metrology Institutes (NMI) for the realization of the Radiofrequency and Microwaves (RF&MW) primary power standard. Since they are not available on the market, NMIs have to design their own systems. It involves the design of complex mechanical structures and of low noise data acquisition systems. Resulting setups allow precision measurements of RF&MW power by applying difficult and time consuming measurement techniques. Weaknesses to be addressed in order to improve the performance, whether in the mechanical structure or in the data acquisition electronics, are not easy to identify. Anyway, they can be found by analyzing the microcalorimeter measurement uncertainty. In recent years, several improvements have been made on the INRIM (Istituto Nazionale di Ricerca Metrologica, Italy) coaxial microcalorimeter with the aim of making its operation more stable and to reduce the measurement uncertainty. Its weak points are here analyzed by means of a comprehensive uncertainty budget. Details are also given on how uncertainty contributions have been determined. The method here applied is general and can be conveniently used in many other fields or applications provided that the analytical model is known. It is useful while designing an experiment and/or a posteriori, to identify the parts of the apparatus and of the measurement set-up that need to be optimized.

Proposal of a Super-Symmetric Microcalorimeter for Single Step Realization of RF Primary Power Standard

The realization of RF primary power standards by means of microcalorimeter technique requires huge measurement times because the necessity of performing in completely separated steps the standard measurement and the system calibration. This procedure is very detrimental for the final measurement accuracy, therefore, in the paper, a new design is proposed of broadband microcalorimeter, which with an improved hardware and convenient new algorithms allows a self-calibration of the system without dismounting/mounting operation. A four times shorter measurement time, without accuracy loss, together with the improvements of the thermal noise rejection and in the measured data correlation, are the most significant results obtainable.

RF/MW Power Standard Realization Without Unitary Efficiency Assumption at DC/LF

Thermoelectric power sensors are widely used in commercial power meters at RF and microwaves, due to their superior robustness, stability, and accuracy if compared with other types of power sensors. Furthermore, their electrical architecture and related performance turned out to be very useful in the realization of the broadband primary power standards as alternative to resistive power sensors, i.e. bolometers. Hereby we present a comparison in term of effective efficiency of a thermoelectric sensor calibrated by applying two different methods of power substitution when used as thermal load in a coaxial microcalorimeter at RF and microwaves. The aim is to test a technology that could enable the realization of a primary RF/MW power standard independently of the assumption of unitary efficiency at the dc (or LF) reference power.

AC Power at Power Frequencies: Bilateral comparison between SASO NMCC and TÜBİTAK UME

A supplementary bilateral comparison measurement on AC Power at 50/60 Hz between SASO NMCC (GULFMET) and TÜBİTAK UME (EURAMET) was performed with the primary power standards of each partner. Measurement methods and setups which are very similar of the participants, measurement results, calculation of differences in the results, evaluation of uncertainties are given within this report.Main textTo 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 CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

$V$ -Band Waveguide Microcalorimeter for Millimeter-Wave Power Standards

This paper describes a recently developed V-band waveguide microcalorimeter that serves as primary power standards at the Korea Research Institute of Standards and Science (KRISS). The design scheme of the waveguide microcalorimeter is presented, and its basic performance is evaluated. The stability of the thermopile module of the microcalorimeter at ambient temperature is measured, and appropriate parameters obtained from a linear modeling are employed to compensate the temperature drift. The thermal performance of an adiabatic waveguide is simulated using a finite-element-method-based tool. A dedicated high-power V-band source module is developed, and its stability and repeatability are evaluated. In order to determine the correction factor of the microcalorimeter, the offset-short method was used and the results are presented. The uncertainty budget of a V-band reference standard at selected frequencies is presented.

Development of an extremely precise buffer amplifier for AC shunt standards at audio frequencies

AbstractThe National Metrology Institute of Japan (AIST, NMIJ) launched a project for the development of AC shunt standards. AC shunts allow the most precise measurement of current. A high‐precision AC shunt is an important component of nonsinusoidal power standards. The AC shunt calibration system helps improve the uncertainty assessments of the national primary power standards. The calibration system design with uncertainties of up to 10 ppm requires a precise buffer amplifier which has uncertainties of up to 1 ppm in the frequency range from 10 Hz to 10 kHz, with other uncertainty components taken care of. The two buffer amplifiers dealt with in this paper were verified to have errors within 2 ppm and uncertainties within 1 ppm in in‐phase and quadrature error in the frequency range from 10 Hz to 10 kHz. This also implies a possibility of reducing both in‐phase and quadrature error at 10 kHz within 1 ppm, by taking advantage of both features. This paper describes the circuit design and evaluation results of two different buffer amplifiers. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(4): 24–31, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21218

Realization and dissemination of high frequency power standard at INRIM

In the High Frequency (HF) field, the primary power standard is maintained through reference sensors calibrated in terms of effective efficiency ηe. These devices are in turn used to transfer the power standard by means of direct comparison on the same matched generator. For this kind of operation, the only knowledge of the effective efficiency of the device is not enough and additional parameters of the reference sensor are necessary.The paper describes the methods and techniques used at INRIM to disseminate the “HF power standard”, with emphasis to all the technical aspects involved, in order to provide a thorough explanation of the procedures implemented.

Improvement of primary power standard through international comparison feedback

The high frequency primary power standard is univocally realized by means of a coaxial microcalorimeter, at least up to 40 GHz. The coaxial microcalorimeter is a broadband measurement system adjusted for effective efficiency measurement of power sensors both of bolometric and thermoelectric type. The critical point in the power standard realization is in the determination of the calibration constant g of the microcalorimeter, a frequency dependent parameter that has huge impact on the accuracy assessment of the standard. The paper proposes a simple but powerful way for improving this accuracy by using the reference values provided by international key-comparisons which the microcalorimeter was involved in.

Development of an Extremely Precision Buffer Amplifier for AC Shunt Standards at Audio Frequencies

The National Metrology Institute of Japan (AIST, NMIJ) has launched the project for the development of AC shunt standards since 2007. AC shunts allow the most precise masurement of current. A high precision AC shunt is an important component of non-sinusoidal power standards which is in progress. The AC shunt calibration system helps improve the uncertainty assesments of the national primary power standards. The calibration system design with uncertainties up to 10 ppm requires a precise buffer amplifier which has uncertainties up to 1 ppm in the frequency range from 10 Hz to 10 kHz with other uncertainty components taken care of. The two buffer amplifiers dealt with in this paper were verified to have accuracies within 2 ppm and uncertainties within 1 ppm in in-phase and quadrature error in the frequency range from 10 Hz to 10 kHz. It also implies that there is possibilities to reduce both in-phase and quadrature error at 10 kHz within 1 ppm, by taking advantage of the both features. This paper describes the circuit designs and the evaluation results of two different buffer amplifiers.

On coaxial microcalorimeter calibration

Primary power standards in the microwave domain are realized using a calorimetric technique, usually identified with the used measurement system, i.e., the microcalorimeter. It is adjusted for measurement of power ratios with a relative accuracy that, after an appropriate system calibration, is of order of 10^-3, at least in the microwave domain (1 GHz-18 GHz). Hereby we describe the calibration process implemented at the Istituto Nazionale di Ricerca Metrologica (Italy) for realizing a coaxial power standard based on indirect heating thermocouples. Particular regard is devoted to describe the nearly ideal thermal load used for determining the microcalorimeter losses and their influence on the measurand accuracy.

Linking Primary Power Standards and Programmable Josephson Arrays

Recently, precision waveforms with accuracies better than 1 part in 107 at power frequencies have been available from series arrays of shunted Josephson junctions operated as digital to analog conv...