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The topic of the article is analysis of circuits for active electrodes used at capacitively coupled measurements. The work compares differences between wet and insulate electrode. There is analyzed circuit for active electrode which uses integrated voltage follower and there are also presented and simulated improvements for proper using this kind of active electrode for capacitively coupled electrode. Each of these simulations was performed in TINA SPICE - based analog simulation program by Texas Instruments. Finally, the article presents a solution for an operational amplifier integrated into the active electrode to prevent saturation of its inputs. This solution ensures to ground operational amplifier input in the case of overrunning threshold value.

This article introduces a capacitive measurement method for objective examination of textile sensor sensitivity within the frequency range associated with various biosignals. The proposed evaluation method is subsequently used to investigate biosignal sensing properties of a basic copper surface sensor and two selected textile sensors made from commercially available and commonly used conductive Shieldex and Elitex fibres. Experiment results indicate that the Elitex-based electrode is more suitable than Shieldex and copper surface electrodes. The signal attenuation of the Elitex electrode is lower by approx. 1–2 dB in comparison to the Shieldex electrode in the 0.5 Hz to 10 kHz frequency range. The copper surface electrode has slightly better signal transmission properties within low frequencies (

A capacitive measurement of the biosignals is a very comfortable and unobtrusive way suitable for long-term and wearable monitoring of health conditions. This type of sensing is very susceptible to noise from the surroundings. One of the main noise sources is power-line noise, which acts as a common-mode voltage at the input terminals of the acquisition unit. The origin and methods of noise reduction are described on electric models. Two methods of noise removal are modeled and experimentally verified in the paper. The first method uses a passive capacitive grounding electrode, and the second uses an active capacitive Driven Right Leg (DRL) electrode. The effect of grounding electrode size on noise suppression is experimentally investigated. The increasing electrode area reduces power-line noise: the power of power-line frequency within the measured signal is 70.96 dB, 59.13 dB, and 43.44 dB for a grounding electrode area of 1650 cm2, 3300 cm2, and 4950 cm2, respectively. The capacitive DRL electrode shows better efficiency in common-mode noise rejection than the grounding electrode. When using an electrode area of 1650 cm2, the DRL achieved 46.3 dB better attenuation than the grounding electrode at power-line frequency. In contrast to the grounding electrode, the DRL electrode reduces a capacitive measurement system’s financial costs due to the smaller electrode area made of the costly conductive textile.

This article presents an analysis of active electrode design for capacitively coupled measurement of bioelectrical signals. It deals with constructing an active electrode using a guard layer to decrease its input's parasitic capacitance. Three dielectric materials (cotton, polyester, wool) were examined under different pressure (1.23 kPa, 3.07 kPa) of the active electrodes. The Common Mode Rejection Ratio (CMRR) analysis of the system using guarded and unguarded electrodes is also investigated. The results show that the guard layer increases the active electrode's gain in the whole measured frequency range for all insulation materials and pressures. An unguarded active electrode reaches a gain of −7.45 dB while using cotton as dielectric material under the pressure of 1.23 kPa compared to the guarded active electrode, which reaches the gain value of −0.47 dB at the same conditions. The measurements of the CMRR prove that the guard layer increases the system CMRR.

The article deals with principle of the heart activity measurement using a piezoelectric sensor. There is an information about design of the device serving for arterial pulse wave measurement. The device allows conversion of an electrical charge from the piezoelectric sensor and offers analog signal preprocessing. The signal is later digital processed to achieve a heart rate of the measured subject.

The presented article deals with the topic of monitoring CO 2 absorption in a closed loop diving apparatus. While partial pressure is monitored in the closed-circuit breathing loop using oxygen sensors, carbon dioxide is not monitored at all. However, higher carbon dioxide or oxygen content in the breathing medium has toxic effects on the organism. CO 2 absorber composition, manufacturing thereof and chemical reactions occurring during CO 2 absorption are discussed - based on this a device for monitoring the exothermic absorber chemical reaction is constructed. The proposed device estimates the time to CO 2 absorber depletion based on the displacement of the chemical reaction zone.

The objective of this study was to explore the possibility of combining the theoretical human arterial model based on electromechanical analogy with real impedance cardiography measurements - the fusion of which would create a per-person adaptable model. Cardiac activity was modeled based on two different sources – the first model (Model No.1) included real-life hemodynamic parameters based on variation of universal aortic pressure, while the second model (Model No.2) was based on real-life aortic flow derived from measurements. Simulated blood pressure propagation in proximal aortic segment was compared with reference pressure values measured by an electronic sphygmomanometer. Model No. 2 was found to be more accurate and better representative of real behavior of the arterial system under normal conditions. Additionally, the blood pressure and blood flow curves directly reflected the variability of the cardiac activity.

Human arterial system simulation models represents a helpful tool for investigating blood pressure and blood flow propagating from the aorta towards upper and lower peripheral vessels. Real-life hemodynamic parameters are used as input for the arterial model based on electromechanical analogy. The mentioned parameters are determined from impedance cardiography measurements carried out on five human subjects. The theoretical model is thus individually adapted using real-life hemodynamic parameter values and the impact of stroke volume and heart rate changes on blood pressure and blood flow waveforms are investigated. We can conclude that the stroke volume influences especially the amplitude of the said curves, whereas the heart rate modifies shape thereof.

With increasing laser power the transient behavior of the optical components becomes more and more important giving rise to investigations in this field e. g. [1 Especially the time dependence of the optical properties which influence the laser beam parameters is of interest In this paper the heating of optical components caused by the absorption of a small part of the laser power as well as the resulting deformation of the phase front of tl laser beam have been studied with finite element analysis. For this the spatial temperature profile the mechanical deformation and the stress of the optical component have been calculated as a fuixtion of laser power laser mode proffle and irradiation time. Using the temperature dependence of the index of refraction the spatially resolved optical path difference compared to the unirradiated component has been calculated with a ray tracing algorithm. The results for various optical components (mirmrs windows coated and uncoated) are given and compared to experimental investigations.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The transient behaviour of optical elements has been investigated under the irridation of high power CO2 laser light. First, the absorption of ZnSe windows and lenses and of copper mirrors has been measured. With these data, time dependent calculations of the optical deformation of the wavefront have been carried out and were compared with experimental results. The different characteristics of ZnSe components and reflecting mirrors are discussed in detail. Finally, a new adaptive optical element is described by means of which the measured optical deformation can be compensated.The transient behaviour of optical elements has been investigated under the irridation of high power CO2 laser light. First, the absorption of ZnSe windows and lenses and of copper mirrors has been measured. With these data, time dependent calculations of the optical deformation of the wavefront have been carried out and were compared with experimental results. The different characteristics of ZnSe components and reflecting mirrors are discussed in detail. Finally, a new adaptive optical element is described by means of which the measured optical deformation can be compensated.