Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.

Impedance matching device provided with reactance-impedance table

Abstract: An impedance matching device is provided, for which the electric characteristics at an output terminal are accurately analyzed. The matching device is provided with an input detector for detecting RF voltage and current at the input terminal, and an output detector for detecting RF voltage outputted from the output terminal. The matching device also includes a controller for achieving impedance matching between a high frequency power source connected to the input terminal and a load connected to the output terminal. The impedance matching is performed by adjusting variable capacitors based on the detection data supplied from the input detector. When the impedance of the power source is matched to that of the load, the controller calculates the output impedance, RF voltage and RF current at the output terminal, based on the adjusted capacitances of the capacitors, a pre-obtained reactance-impedance data and the detection data supplied from the output detector.

Current approaches to analogue instrumentation design in electrical impedance tomography

Abstract: Electrical impedance tomography (EIT) is a novel medical imaging method, which allows reconstructed tomographic images of the internal impedance of a subject to be made with the use of a ring of electrodes. High precision impedance measurements are needed, because the image reconstruction process is ill-conditioned and small errors in measurement can lead to large errors in the final image. In practice, there are formidable instrumentation problems, due to the interaction of finite current drive output impedance, recording amplifier common mode rejection, and unequal skin - electrode impedances. A number of different EIT systems have been constructed or are under development. These employ differing strategies, such as additional electrodes, multiple electrode current injection, or recording at multiple frequencies, to improve image accuracy. This paper reviews the nature of the instrumentation problems and the designs employed by differing groups in attempting to overcome them.

Instruments for transcutaneous and subcutaneous investigation and treatment

Abstract: Instrument provides three modes of operation: (1) An impedance measuring probe and meter and a tone generator, the frequency of which is a function of the skin impedance at the test point A squelch circuit disables the tone generator when the probe is not in contact with the skin; (2) A sensitive voltage measuring meter can then be switched on using the same indicator The polarity of the voltage at the probe is indicated by differently colored lights; (3) A voltage generator can then be switched on to provide bursts of electrical energy to the test point Multiple electrodes are also provided

A Direct Three-Phase Circuit Analysis-Based Fault Location for Line-to-Line Fault

Abstract: From a direct three-phase circuit analysis, an accurate fault-location algorithm has been obtained for the line-to-line fault as an extension of the author's previous work for line-to-ground fault location. Robustness of the proposed algorithm to load impedance uncertainty is enhanced by the introduction of impedance compensation using voltage and current measurements. Simulation results show a high degree of accuracy and robustness to load uncertainty.

An Analysis Protocol for Three-Electrode Li-Ion Battery Impedance Spectra: Part I. Analysis of a High-Voltage Positive Electrode

Abstract: A key for the interpretation of porous lithium ion battery electrode impedance spectra is a meaningful and physically motivated equivalent-circuit model. In this work we present a novel approach, utilizing a general transmission line equivalent-circuit model to exemplarily analyze the impedance of a porous high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode. It is based on a LNMO/graphite full-cell setup equipped with a gold wire micro-reference electrode (GWRE) to obtain impedance spectra in both, non-blocking conditions at a potential of 4.4 V cell voltage and in blocking configuration achieved at 4.9 V cell voltage. A simultaneous fitting of both spectra enables the deconvolution of physical effects to quantify over the course of 85 cycles at 40°C: a) the true charge transfer resistance (RCT), b) the pore resistance (RPore), and c) the contact resistance (RCont.). We demonstrate that the charge transfer resistance would be overestimated significantly, if the spectra are fitted with a conventionally used simplified R/Q equivalent-circuit compared to our full transmission line analysis.