Marian Kampik, Michal Grzenik
Thermal AC voltage standards with calculable AC-DC transfer difference in frequency range from 10 kHz to 1 MHz

The paper presents design and basic metrological properties of three thermal AC voltage standards with nominal input voltages 1.5 V, 3 V and 6 V. Each standard is composed of a range resistor connected in series with a single junction thermal converter (SJTC). The AC-DC transfer differences of these standards are calculated in frequency range from 10 kHz to 1 MHz.

Lluis Ferrer-Arnau, Xavier Roset, Juan Mon-Gonzalez, Vicenç Parisi-Baradad
Decimator filter based on B-splines

The cascaded integrator-comb (CIC) filters are widely used as decimators in many applications, such as in delta sigma AD converters to decimate the sampled signal on its output. One problem with these filters is that by increasing its order to improve the signal attenuation in the stop band, worsens the passband response. In this paper we propose a so-called least-squares filters (LSF) based on B-splines to improve that response, compensating for CIC filter drop and flattening the magnitude response of the pass band. We also study the relationship between the CIC filters, otherwise called moving average, and the B-splines expanded by an integer factor. We show that the least-squares filters based on B-splines can be decomposed in CIC filters, with a higher order than the splines used, plus a compensator filter. Another important contribution of this work are the FIR approximations of anti-causal IIR filters needed to implement LSFs.

Giovanni Betta, Pietro Burrascano, Luigi Ferrigno, Marco Laracca, Marco Ricci, Giuseppe Silipigni
On the Use of Complex Excitation Sequences for Eddy Current Testing

Eddy Current Testing (ECT) is a Non Destructive technique widely used in many industrial application fields in which it is very important to detect the presence of thin defects (generally called cracks) in conductive materials. Features of this technique are the cost-effective implementation and the kind of retrieved measured data that make possible estimating geometrical characteristics of a crack as position, length, width and depth. The analysis of these characteristics allows the user to accept or discard realized components then improving the production chain. To accomplish for this task some aspects have to be taken into account during the measurement process. They mainly concern with the realization of suitable measurement setup and post processing stages. As far as the measurement setup is concerned, crucial aspects are the choice of measurement and excitation devices. As for the former, in the past years the literature deeply explored many types of measurement probes highlighting advantages and disadvantages of different solutions. The choice of optimized excitation devices and strategies is now interesting recent studies about Non Destructive ECT (ND-ECT): together with common aspects as the amplitude and the frequency of the exciting signal, recently the attention has been paid to issues as the type of signal to be adopted. In particular it has been found as the use of complex excitation signals, meant as signals different from the sinusoidal ones and with wide frequency content, might raise eddy current responses trying to support the measurement, detection and characterization stages when “difficult cases” are explored (i.e. very short or annealed cracks). In this paper the authors propose an experimental comparison of different excitation signal designed to improve the quality of experimental data when difficult cases are experienced (such as annealed and small cracks) and consequently to obtain a more reliable extraction of defects geometrical features.

Andrea Zanobini, Lorenzo Ciani, Marcantonio Catelani
Hypothesis Test on the ratio between two measurement uncertainties

In a measurement context often it is fundamental to verify if two independent measurement processes give origin to the same uncertainty. The comparison between these two uncertainties is important, for instance when we use two or more different instruments. We apply this method to the uncertainty of a digital oscilloscope measuring rise/fall time of a signal. We apply this test to verify this property if it is requested by other important hypothesis tests like that about the difference between the measurand estimators. This technique is also the base to the ANOVA (ANalysis Of VAriance) procedure. Such statistical tools are widely adopted in the measurement since to draw conclusions from experimental results.

Normandino Carreras, Antoni Manuel Làzaro, Spartacus Gomariz
Design of seismic acquisition system for volcanology

This paper presents a new design based on acquisition system of the volcanic seismic data. Mainly, this system is composed of a microcontroller to manage the peripherals, a module to acquire the information of seismic sensor and a module of communications that contains the RF and GPS system. The prototype aims to be a very low power system allowing also working during a complete year.