Valeriu David

Wearable impedance analyzer based on AD5933

In this paper a system for measuring impedance, based on AD5933 circuit is presented. The impedance measuring range is between 9 Ω and 18 MΩ for a 1 kHz ÷ 100 kHz frequency range. Possibilities of expanding this range of measurement are also presented in the paper. The system calibration is automatic and the relative error of the impedance modulus measurement is in the range ±2%. Measured impedance main parameters are shown locally on an OLED display but can also be stored in an SD memory card for further processing. The system is portable, modular and adaptable to a large number of applications.

Investigation of the textile structures with different design used in electromagnetic shielding

This paper describes a study on the development of few textile structures and the possibility to use them in electromagnetic shielding and protection equipment manufacturing. The long-term exposure to electromagnetic waves can seriously damage a persons health. The goal of this research is: to evaluate the implementation possibilities of new materials and composite structure (using amorphous magnetic materials, carbon powders stainless steel yarns and copper yarns), and also to achieve a protective composite textile material with absorbing properties, in order to protect human body and residential areas. Conductive materials have different absorption and reflection behaviors: metals are known for having high reflectivity, whereas carbon fibers and conductive polymers are known for having a high absorption behavior. This general trend was also observed in the results obtained. Conventional textile materials are not suitable for this purpose, but their modification and transformation in composites or other type of structures can be useful.

Heart rate variability monitoring due to 50 Hz electromagnetic field exposure and statistical processing

This study investigates the influence of the 50 Hz electromagnetic exposure on heart rate variability (HRV). Thus, we recorded and preceded the ECG signals for 44 volunteers both in high and normal field exposure. The acquisition system and the QRS detection algorithm were developed by the authors with the view to be used in this study. Spectral measurements of the HRV revealed a significant increase (Students t-test: Pt=0.00l; Mann-Whitney U-test Pu=0.00l; average difference D=16.857) in the power of the HF components and significant reduction in the power of the low-frequency (Students t-test: Pt=0.003; Mann-Whitney U-test Pu=0.003; average difference D=-14.906) on volunteers exposed compared with unexposed one conditions.

Walls effect over the specific absorbtion rate in the human head due to mobile phone exposure

The purpose of this paper is to determine the specific absorption rate (SAR) in the human head in 10 g of mass tissues due to mobile phone exposure with walls nearby. The mobile phone was modeled as a λ/4 monopole antenna placed at a distance of 1 mm from the human head and the SAR values were determined using CST software for two GSM frequencies, 900 and 1800 MHz taking into consideration different placements of the walls in the head vicinity and antenna positions too. As a particular application SAR was determined when the human head is situated inside a metallic cage whose dimensions are comparable with an elevator cabin.

An portable device for ECG and photoplethysmographic signal acquisition

This paper presents a low-cost, portable, light weight, high performance device developed by the authors for electrocardiographic (ECG) and plethysmographic signals recording. The proposed system was tested and compared with clinical grade amplifiers, also noise and robustness tests have been conducted. The prototype permits both on line and off line working mode, being capable to record ECG data with high fidelity in various environments.

Dynamics analysis of heart rate during Magneto-Therapy session

In this paper we determined and analyzed the Heart Rate (HR), based on the Electrocardiographic signals (ECG) recorded before, during and after magneto therapy sessions. The purpose of our study is to determine some possible changes in the biological signals in the case of people exposure to magnetic fields. Thus, we determined and analyzed Heart Rate dynamics, both in time-domain and in frequency domain comparing the obtained results before, during and after the Magneto Therapy procedures.

ECG signal processing using Wigner function

This paper presents a virtual instrument for biosignal systems monitoring. Due to various artifacts, ECG signal acquired by data acquisition systems may contain high level of noise. These conditions, in real life situations, may vary from no noise to extreme amount of noise corrupting the biosignals. Thus, ideal ECG signal processing systems must consider various levels of noise and should have a technique to deal with wide range of noisy situations. In this paper, we will present a method that works well with different signal to noise ratios ranging from -3 dB to 20 dB.

Estimation of human exposure in some electromagnetic environments

On the basis of the measured levels of electromagnetic environment due to radio-communication transmitters and mobile communication systems (90 MHz ÷ 2.2 GHz), both the relative exposure levels - RE and the relative specific absorption rate -RSAR were calculated. The specific absorption rates - SAR were determined by simulations made with CST Microwave Studio software using some head models: a spherical model, a homogeneous SAM model and a complex head model proposed by authors. In this scope it was proposed a virtual human head model using successive magnetic resonance imaging (MRI) sections. The investigations were performed in a large frequency range including typical exposure fields in some areas. Thus, it was made a comparison between SAR, obtained using two simple homogeneous human head models and the correspondent results obtained using the proposed complex model. The determined parameters were also compared with those recommended by the International Commission on Non-Ionizing Radiation protection-ICNIRP.

QRS time detection using Wavelet Multiresolution Analysis for determining HRV in case of ECG signals with high level noise

In this paper we studied the influence of noise when extracting QRS from electrocardiographic (ECG) signal by means of Wavelet Multiresolution Analysis. Thus, we have made a time detection of QRS waves and heart rate both on a electrocardiography signal (ECG) and on the same electrocardiography signal over that overlapped different types of noises (white noise, 50 Hz noise, Gaussian noise and their combinations).

Electromagnetic emissions due to electrosurgery

Electrosurgery devices are an important part of surgical interventions in the modern medical service; however the benefits of using such technology are accompanied by side effects like electromagnetic pollution of the hospital environment. As a consequence, the maximum admitted levels of electric and magnetic fields for general public and occupational exposure could be exceeded in some cases and the risk of electromagnetic interference with medical devices rises while implementing electrosurgery in the operating room. In this paper we address the characterization of the electromagnetic emissions from an electro surgical device at different distances and determine the maximum field levels for different operating modes of the device with a monopolar scalpel. Also, the surgeons exposure while performing electrosurgery was determined to be much higher than occupational exposure limits imposed by international standards.