Rok Tavčar, Dušan Agrež, Samo Beguš
Acoustic thermometer with a single waveguide

This paper presents implementation and testing of the acoustical thermometer with a single waveguide. Proposed design has a few specific advantages against other types of acoustic designs with waveguides, such as smaller size, better sensitivity and the same common sound path. The paper describes each advantage and tests used to determine their usefulness. Finally it shows how to deal with disadvantages of this design, such as weak return signals and possible coincidences of the return signals. The instrument was calibrated at ice point and then tested in oil bath from -30 °C to 120 °C. In steady states it has standard deviation of 0.050 °C with 66 independent readings per second. Stability of the bath is 10 mK and uncertainty of the reference thermometer is 0.003 °C.

Alexandru-Constantin Podaru, Valeriu David, Oana Neacsu
Comparison between Electrocardiographic and Photoplethysmographic Peaks Intervals

A low-cost wearable system has been developed, that was used to record simultaneously the electrocardiographic signal (ECG) and photoplethysmographic signal (PPG).The prototype permits an offline working mode, being capable of recording both signals, ECG and PPG, on a memory card, using Arduinonano board. The recorded signals consist from the first derivation of ECG and the PPG signal collected from the left-hand index finger. First, we collected signals from several subject, in the same manner for all, before detecting the interested peaks from those signals, we removed the noise, from ECG to avoid false or missed peaks that can appear during the recording process, and we determined the RR peaks and R-to-R time interval. Also from PPG signal, we determined the PP peaks and P-to-P time interval. Using these results we determined the differences (ε) between the R-to-R and P-to-P time intervals, in order to observe which is the greatest difference between these parameters and if we can replace the RR intervals with PP interval. From the obtained results, we concluded that the majority of the differences are lower than 3%, about 92% from the total of the detected intervals. Also we detected that 5% of the differences are between 3% and 5%, and only 3% are above 5%.

Ovidiu Bejenaru, Eduard Lunca, Valeriu David
Characterization of the Electromagnetic Interferences due to a Public Lighting System

With a view to characterize the electromagnetic interferences (EMI) due to a model of Light Emitting Diode (LED) lamp used in street lighting, measurements of radiated emissions were conducted both in situ and in an Electromagnetic Compatibility (EMC) laboratory. The in situ measurements were carried out using an Anritsu MS2724B spectrum analyzer in conjunction with a directional antenna, in the frequency range from 20 MHz to 200 MHz, at 10 m distance from a number of LED lamps. The EMC laboratory measurements were conducted in compliance with the European Standard EN 55015, “Limits and methods of measurement of radio disturbance characteristics of electrical lighting and similar equipment”. The paper presents measurement results obtained in the two situations, which indicate that the emissions from the considered LED lamps exceed the imposed EMC limits and so EMI problems appeared by using these products.

Ionel Dumbravă, Georgiana Roşu, Ion Pătru, Aurelia Scornea, Octavian Baltag, Andrei Marinescu
Calibration of Magnetic Field Sensors up to 10 kHz Based on 50 Hz Helmholtz Coils

Helmholtz coils (HC) are used to develop uniform magnetic fields for a variety of research applications. Helmholtz coils can be easily constructed and the fields easily calculated. This makes them especially useful in calibrating sensors and numerous other low-frequency magnetic-field testing applications. Such a calibration system with Helmholtz coils can be found in ICMET, operating at a frequency of 50 Hz. Recently, the issue was raised for calibration of certain measuring devices up to 10 kHz frequencies needed for measurement in industrial applications such as induction hardening of metal parts. The first part of the paper presents theoretical analysis on the volume confining the space where the magnetic field components have a predetermined deviation (a 2% threshold) from the center of the classical Helmholtz system followed by a comparison with a 3D FEM simulation and measurement of HC field. The second part describes the parameters identification and the resonant power supply used to significantly reduce the excitation output required for the Helmholtz coil system at these frequencies.

Iuliana-Delicia Dîrlau, Oana Beniugă, Burlică Radu
Electromagnetic Stress Induced by Surface Discharges on Water Film

This paper deals with analysis of cold plasma surface discharges used as depollution techniques in order to induce oxidation/ reduction reactions in polluted water, without catalysts involvement. The paper is a statistical assessment of dependency between the electromagnetic stress induced by electrical surface discharges on water films and the distance from the discharge point. The electromagnetic field waves are generated by cold plasma electrochemical reactors surface discharge type.