Romano Giannetti

Transmittance photoplethysmography and pulse oximetry with near infrared laser diodes

Photoplethysmography and pulse oximetry are widely used techniques for noninvasive monitoring of heart rate and peripheral oxygen saturation. Over the last years we have been working onto the application of near infrared range wavelengths to replace those of the classical pulse oximeters. The development of laser diodes based sensors, processing algorithms, a calibration procedure, and the comparison with a commercial pulse oximeter, have been followed by a set of experimental studies. The results exposed here demonstrate the applicability of transmittance photoplethysmography and pulse oximetry using laser diodes emitting at specific wavelengths for a wide range of situations.

Conducted and radiated interference measurements in the line-pantograph system

We present the results of a measurement campaign aimed at investigating electromagnetic interference (EMI) phenomena in the interaction between overhead railway power supply lines and pantograph. In order to obtain such data, an experimental setup was assembled in a shielded room, consisting in a short section of overhead line and a full scale pantograph. One of the most interesting results consists in the observation of a very significant (both from the qualitative and the quantitative point of view) difference between the EMI behavior in the switch-on (pantograph going up) and switch-off (pantograph going down) transients.

Characterization of the Accommodation Effect in Soft Hysteretic Materials Via Sensorless Measurement Technique

The well-known voltamperometric method has only been used so far in the identification of symmetric hysteresis cycles for reasons that are explained in the main text. This paper extends the sensorless measurement method to the characterization of asymmetric loops, without losing the main advantage of this technique, i.e., the low-cost setup and the simplicity of the procedure. The current through-and the induced voltage on-the primary and secondary coils, which are wound around a magnetic core, are the measurands. Moreover, by carefully choosing the input signals, so that a series of major loops is defined along the whole B - H measured path, a way is suggested to avoid the problems caused by the dc offset of the instrumentation chain and to reduce the uncertainty in the determination of the initial state of magnetization. Both the offset and the initial magnetization state are necessary for a correct reconstruction of the induction field. A complete analysis of the capabilities and critical aspects of the proposed measurement procedure is carried out through a theoretical discussion supported by simulation and experimental results. The measurement of nonsymmetric cycles and their accommodation are shown and discussed as the final objective of the proposed approach.

Sensorless Measurement Technique for Characterization of Magnetic Material Under Nonperiodic Conditions

This paper deals with the sensorless characterization of magnetic materials under nonperiodic conditions. A volt-amperometric method based on general physical principles has been adopted to do the measurements. Starting from the concept of magnetic hysteresis as a multibranch nonlinearity with nonlocal memory, we provide a description of the proposed measurement procedure, focusing on two significant topic points: 1) the determination of a well-known (within a certain interval of confidence) initial state of magnetization and 2) the effect on the final experimental results of the offset introduced by the instrumentation. Finally, we present experimental results done on a sample of soft ferrite, showing how the method is capable of measuring phenomena like accommodation or noncongruency of minor loops.

A new method to characterize magnetic hysteresis in soft ferrites up to high frequencies

Characterization of magnetic cores is an indispensable task in order to securely accomplish the requirements of a power electronic design and prevent failures. The hysteresis cycle of the material is one of the more complex features to characterize due to the well-known nonlinear and memory effects; moreover, there is a less known but noticeable dependence of the B-H relationship with time. This curve is easily obtained at low frequencies (up to 10 kHz) by means of a well-known traditional method. However, there is a major obstacle when trying to operate at higher frequencies in this manner due to the cost and difficulty of operation of high-frequency-high-voltage generators. In this paper, a new method for measuring hysteresis based on a quasi-sinusoidal generator that allows us to reach much higher values in frequency with a simple setup is presented.

Identification of parameters in a Rogowski coil used for the measurement of partial discharges

The Rogowski coil is a simple and inexpensive device that can be adapted to measure high frequency currents such as those created by partial discharges in dielectrics. It has been demonstrated in previous works that the Rogowski coil can be self-integrating when used at high frequencies and can be tuned to measure partial discharges without the need of cumbersome electronic devices. The aim of this paper is to explore the possibilities of obtaining better measurements simply changing the electric parameters and hence, the geometry of the coil. In the process, the inductance, mutual inductance, resistance and capacitance are written in function of geometric variables. Then, a bode plot simulates the effect of changing some of these variables and the results are commented focused on the pursued objective.

Line-pantograph EMI in railway systems

At present, the EN50121 standards are the main reference for electromagnetic compatibility in European railway systems. These standards should improve as technology and testing develops. Therefore, major sources of EMI in a railway environment need to be better understood. This study is complex because many different railway power systems exist in Europe (1.5 kV DC, 3 kV DC, 15 kV 16.7 Hz, 25 kV 50 Hz). European railways are using new control and communication systems, and electromagnetic compatibility problems should be carefully studied and solved.

Ultra low noise current sources

The current sources which are normally used in research laboratories are not suitable for low noise measurement systems because of the unacceptable level of low frequency noise which they introduce in the measurement chain. The most important source of low frequency noise in such instruments is the solid state device (usually a Zener diode) which is used as voltage reference. By using a novel circuital topology in which a lead battery which does not supply current is used as voltage reference, we have been able to design an ultra low noise current source characterized by a low-frequency noise level some orders of magnitude lower than that of similar commercial instrumentation. The design, realization and testing of such current source is presented.

Numerical characterization of dynamic hysteresis loops and losses in soft magnetic materials

This paper deals with the characterization of dynamic loops shapes and losses in soft magnetic materials. An experimental and theoretical analysis has been done in order to describe static and dynamic hysteresis on soft ferrite cores. A parallelogram-loop-based hysteresis modeling is described and discussed. The possibility of the model to include vector hysteresis and the related properties are then discussed, with particular attention to the case of a rotating magnetic field into an isotropic and anisotropic medium.

Electrical characteristics of silicon nitride on silicon and InGaAs as a function of the insulator stoichiometry

Abstract The interface state density along the semiconductor energy gap and the fixed charge were evaluated in SiN x /InGaAs and SiN x /Si interfaces. The insulator layer was deposited by plasma-enhanced chemical vapour deposition (PECVD) using several ammonia / silane gas ratios. In both the samples the measurements revealed two main peaks of interface states whose height is a function of the insulator layer stoichiometry. Further analysis by infrared and Auger electron spectroscopy and electron spin resonance measurements enabled the peaks to be identified as the two silicon-related defects in silicon nitride cited in the literature. The nitrogen dangling bonds were found to affect the fixed charge of the structure. The role of hydrogen in passivating silicon and nitrogen dangling bonds will also be discussed.