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N. Hlupic
A SAMPLING METHOD FOR HIGH ACCURACY AC MEASUREMENT

The method presented here is intended for high accuracy measurement of all parameters of a low frequency (method was tested up to 500 Hz) sine wave. It is relatively simple and, because of its exceptional resistivity to the random errors of samples, applicable for use similarly in calibration laboratories and less demanding measurements. Uncertainty of 10 ppm for all parameters of a sine wave is an ordinary result obtainable with this method, so it can be used for calibration of almost all AC calibrators and insurance of traceability. The only notable disadvantage of this method is relatively long duration of sampling (about 45 s), what makes this method suitable only for measurement of signals with time-invariant parameters.

Valery A. Granovsky, Tatiana N. Siraya
NOISE CHARACTERISTICS IN ELECTRICAL MEASUREMENTS: METROLOGICAL APPROACH

Metrological approach to the analysis of noise is presented. It is based on the time-domain approach for random processes, which is valid both for stationary and non-stationary cases. The asic functional model is proposed as reproducing kernel (RK) Hilbert space H(R), produced by the correlation function R(s, t) of random process x (t). This space with the specific inner product provides an isomorphic representation of the random process x (t). Several typical models of noise are suggested, including White noise, Brownian motion, Markovian, and 1/f – type processes. The corresponding RK-Hilbert spaces are studed. These RK-norms are recommended as the main characteristics for the noises, which are subordinated to the corresponding typical processes. In particular, the set of the norms and estimates includes both well-known characteristics, such as sample variance and Allan variance, and some new characteristics, such as “Markovian” norms. The case is also considered when several norms (characteristics) from this set are valid. Thus one can employ several norms simultaneously.

Alexandru Salceanu, Valeriu David, Liviu Breniuc
STUDY ON CERTAIN PARAMETERS INFLUENCING REPEATABILITY AND COUPLING IN ESD TESTS

The main target of our approach is to store (using a good 500 MHz scope with connectivity facilities and a complex experiment set-up recommended by IEC) more than 100 ESD discharge waveform, in order to be compared and to identify the basic factor of influence for the so much disturbing rising slope, important for modelling, prediction, repeatability and timesaving experiments.

Alexandru Salceanu, Mihai Cretu, Liviu Breniuc
CONSIDERATIONS ON THE INFLUENCE OF THE GROUNDING SET-UP CONFIGURATION ON ESD SUSCEPTIBILITY

Some unexpected failures during ESD tests upon a sensitive fluxgate magnetometer leaded to measurements of the ground potential of the three PCBs, composing our DUT. A significant improvement of the minimum discharge voltage causing errors was obtained only after reducing the impedance of the shielded internal ground lead and equalizing the lengths of the grounding cables connecting the three “shelves” to the “ESD common point ground”. RF measurements techniques and results, graphics, models and equivalent circuits are presented.

Kresimir Malaric, Roman Malaric, Antonio Sarolic
TEM-CELL FOR ELECTROMAGNETIC MEASUREMENTS

Use and application of the TEM-cell has been described. The cell can be used for calibrating small antennas, for immunity and emission testing. It has frequency response up to the first cut-off frequency, which in our case is 485 MHz, but can still have useful areas at higher frequencies (900 MHz). Laboratory experiments as well as commercial testing of the equipment such as cellular phone, IC boards, or small electronic devices up to 5 cm in height are possible. It provides homogenous electromagnetic fields with TEM (transversal electromagnetic mode) distribution, similar to the free space. It has a shield to prevent radiation from the outside, which would interfere with the measurement. Electric and magnetic field inside the cell can be accurately predicted using numerical methods. The measurements of TEM-cell, designed and made at the University of Zagreb, Croatia, of return loss and standing voltage ratio were done. Measurement setup and the method have been explained.

Marinel Temneanu, Traian Balan, Dana Balan, Cristina Temneanu
FUZZY VERSUS NEURAL NETWORK MAGNETIC MODEL IN IRON LOSSES PREDICTION

This paper emphasis the possibility to use both fuzzy and neural network based magnetic models in the prediction of the iron losses. The predictions are compared to the measured output for different magnetic materials and induction waveforms. Comparable results have been obtained proving the capacity of both techniques to describe the complex magnetic behavior of the materials being tested.

Marinel Temneanu, Cristian Zet, Mihai Cretu, Cristian Fosalau
IRON LOSSES MEASUREMENT USING SAMPLE AUTO-RANGING DATA ACQUISITION TECHNIQUES

Being one of the most important quality parameters of magnetic materials, iron losses, and consequently iron losses measurement, are extensively treated in scientific papers. There are many experimental set-up arrangements and also data processing algorithms proposed in order to improve the accuracy of measurement results. A sample auto-ranging data acquisition technique, implemented using National Instrument support, is presented in this paper. The experimental results obtained with three different A/D converters (12, 10 and 8 bits) are presented and compared with the results obtained by using the classic acquisition and processing algorithm.

Lech Hasse
MEASUREMENT OF COHERENCE FUNCTION BETWEEN NOISE CURRENTS OF TRANSISTORS

Relationships between input and output noise parameters of a twoport expressed by correlation and coherence functions has been described. Low noise transimpedance amplifiers (current-to-voltage converters I/V) are used to measure base (gate) and collector (drain) noise currents of transistors in the low frequency range. To reduce an influence of inherent noise of these amplifiers an additional buffer amplifier with special noise properties can be introduce to the input channel of measurement system. A supplementary measurement of the input noise voltage (besides input noise current) can also be used to improve the accuracy of coherence function measurement. To estimate the coherence function with a suitable accuracy adequate digital signal processing procedures should be used.

F. Galliana: P. P. Capra
A TEMPERATURE, HUMIDITY AND PRESSURE INDEPENDENT 1 GW STANDARD RESISTOR: REALIZATION AND PRELIMINARY RESULTS

At IEN a temperature, humidity and pressure controlled standard resistor starting from a 1 GW commercially available resistive component was developed; it is particularly suitable as travelling standard for high value resistance measurement inter-comparisons. It was developed inserting the component in a hermetic container in which temperature, relative humidity and pressure are maintained at level of respectively (25 ± 0,01)°C, (7 ± 1)% and 980 hPa. The preliminary results of the measurements with four measurement voltages performed on the standard showed a short-term stability (24 hour) of about 5×10-7 and mid-term stability (1 month) of about 3×10-6.

F. Cabiati, V. D'Elia
APPLICATION OF ACTIVE COMPENSATED FOUR-COAXIAL CABLES TO AC RESISTANCE STANDARDS COMPARISON

The general features of active connection structures based on four-coaxial cables are summarised and their application to four-port resistance standards to allow them to be compared by means of a conventional transformer bridge is shown. As a test of the measurement method, a comparison between the easurements performed at IEN and at the CTU on a well characterised resistance standard with nominal value equal to the quantised Hall resistance at the i = 2 plateau (12 906,4 W) has been carried out. Some details about the eference resistor, the calculable resistors and the measuring systems are reported together with the results of the comparison.

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