Krzysztof Musiol, Andrzej Met, Marian Kampik
A Study on the Potential Use of Commercial Digital Two-Phase Generators

Two commercial two-phase digital AC voltage sources, WW2572A from Tabor Electronics and SYS-2722 from Audio Precision, were tested for their potential use in impedance comparator bridges. The mutual relative stability of magnitudes and phase shifts of their output voltages were evaluated. Results of relative amplitude and phase shift stability measurements prove that it is possible to obtain uncertainty of impedance comparison at 10^-5 level?using the WW2572A or SYS-2722 as the two-phase AC voltage source in the balanced comparator bridge.

Martin Parker, Andrei Pokatilov, Toomas Kübarsepp, Olev Märtens, Andrei Kolyshkin
Investigation of planar coil for eddy current conductivity measurements in wide frequency range

Several planar coil designs have been investigated for the application in accurate AC conductivity measurements in the wide frequency range. The measurement method is based on the eddy-current probe-coils solutions proposed by Dodd and Deeds. The coil parameters affecting the performance of the model in the specified frequency range from 30 kHz to 720 kHz have been investigated.
Different designs have been used including coils on a printed circuit board (PCB), coils on a flexible substrate and on-site manufactured coils winded from a copper wire. The goal was to reach the inductance of the different coils to match the best-accuracy of the measuring instrument. Amongst the others, the important factor was to keep the diameter of the coils suitable for the practical applications.

Luca Oberto, Luciano Brunetti, Claudio Calosso
Study and characterization of a microcalorimeter thermostat

A high-accuracy adiabatic microcalorimeter has been developed at Istituto Nazionale di Ricerca Metrologica (INRIM, Torino, Italy) for the realization of the radio frequency and microwave power primary power standard. The apparatus is intended to evaluate the efficiency of proper power sensors of thermoelectric or bolometric type by measuring their losses in terms of heat produced. These kind of measurements require a good thermal stabilization of the measurement chamber, therefore a dedicated thermostat has been designed, assembled and characterized at INRIM in order to obtain a thermal stability of 1 mK on a daily basis.

Tomaz Lusin, Dusan Agrez
Estimation of the Amplitude Quotient of Signals with Common Frequency

The paper presents simple single-step algorithms for fast measurement and estimation of the amplitude ratio of the sinusoidal signals with the same frequency from two channels. The idea of the systematic error reduction with the weighted amplitude DFT coefficients around the component peaks is used in the comparative measurement procedure. Paper analyses and compares the systematic bias errors and noise error behaviors of the amplitude quotient estimation changing the order of Rife-Vincent windows class I, which are designed for maximization of the window spectrum side-lobes fall-off. The minimal bias errors are shown in relation to the number of signal cycles in the measurement interval.

Jaroslav Bohacek
Measurement of Frequency Dependences of Low-Value Four-Terminal Resistance Standards

A 10 Ω quadrifilar resistor with calculable frequency dependence served as a reference in measurement of frequency dependences of resistance standards ranging from 1 Ω to 0.01 Ω in a frequency range up to 10 kHz. In this measurement, a step-down method based on successive 10:1 comparisons of the standards by means of a transformer bridge was used. Ratio arms of this bridge being formed by an eight-decade, two-stage inductive voltage divider, a small variable voltage injected into one connecting lead of the ratio winding of the divider serves for quadrature balancing.