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.
In this paper, the new system developed at CEM for the calibration of electric charge meters is presented. Two different approaches are adopted. The first one is based on the charge of a standard capacitor, the other one in the generation of a known current during a specific time.
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...
The most accurate generation of dc currents in the lower ranges is performed with the capacitance-charging technique. Implementations of the method are typically limited to an upper current in the 100 pA range. Here we present a range extender which can be employed as plug-in in existing setups. The extender permits to scale the current of a ×10 factor and reach the nA range. Results of calibration of low-current meters with and without the use of the extender are reported.
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...
The paper describes the evaluation of the uncertainty and calibration results three phase high precision comparator of the electrical power which is one of the main parts of the Secondary Standard of Ukraine of the unit of the electrical power with using of the State Standard of Ukraine of the unit of the electrical power.
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...
The paper discusses the problem of cumulative averaging (CAV) of digital signals after the analog to digital conversion with dither signal. The CAV algorithm performs three operations: division of the signal into a set of repetitions, synchronization of sectors of each repetition and cophasal averaging of samples. The influence of non-ideal synchronization of digital sectors on the value of samples of signal being a result of CAV was assessed. A dependence determining the variance of the signal value after averaging was given because of synchronization error. In the case of sinusoidal...
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.
This paper presents a calibration method with a special search coil used at the Czech Metrology Institute (CMI) for calibration of AC magnetic field meters in the range of frequencies up to 50 kHz. Special attention is given a) to the construction of magnetic flux density standards, which are used for generating the AC magnetic flux density for frequencies up to 3 kHz and for the frequency range from 3 kHz up to 50 kHz, b) to a description of special search coils used for precise measurements of the generated AC magnetic flux density, and c) to the analysis of sources of uncertainty....