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.

Optical reading apparatus with automatic gain control circuit

Abstract: In an optical reading apparatus having a reading sensor for converting optically readable information into an electrical analog signal, an automatic gain control circuit is provided to maintain the amplitude of the electrical signal constant. The gain of the automatic gain control circuit is controlled such that the average or peak voltage of the electrical signal derived from the reading sensor is detected and held until next scanning effected by the reading sensor so that a variable impedance element included in the automatic gain control circuit will be controlled in accordance with the held voltage to maintain the amplitude of the electrical signal constant.

Silicon equivalent ptc circuit

Abstract: A series current regulator with an on-silicon temperature sensor (102) formed over current battery protection device (100) The protection device (100) regulates current in a pass element (101) linearly while sensing the junction temperature of the pass element (101) If the temperature of the pass element (101) reaches a predetermined threshold, the on-silicon temperature sensor (102) actuates a switch (104) which causes the pass element (101) to go into a high impedance mode The protection device offers advantages over positive temperature coefficient (PTC) and further includes faster trip time and lower leakage current

Current source design for electrical impedance tomography.

Abstract: Questions regarding the feasibility of using electrical impedance tomography (EIT) to detect breast cancer may be answered by building a sufficiently precise multiple frequency EIT instrument. Current sources are desirable for this application, yet no current source designs have been reported that have the required precision at the multiple frequencies needed. We have designed an EIT current source using an enhanced Howland topology in parallel with a generalized impedance converter (GIC). This combination allows for nearly independent adjustment of output resistance and output capacitance, resulting in simulated output impedances in excess of 2 GΩ between 100 Hz and 1 MHz. In this paper, the theoretical operation of this current source is explained, and experimental results demonstrate the feasibility of creating a high precision, multiple frequency, capacitance compensated current source for EIT applications.

High impedance fault detection apparatus and method

Abstract: Apparatus is provided for detecting the presence of a high impedance arcing fault on an electrical circuit, particularly a high voltage power line. Detection of a high impedance fault is realized by monitoring the high frequency components of the alternating current in the circuit, and evaluating the high frequency components of each cycle of the alternating current using a microcomputer operating in accordance with a program of instructions, to determine the occurrence of a significant increase in magnitude of the high frequency components, and then to determine whether the increase exists for a prescribed period of time and follows a prescribed pattern. The high frequency components are monitored using a current-to-voltage transducer coupled to the electrical circuit, bandpass filters coupled to the transducer, and an analog-to-digital converter providing digitized samples of the filtered transducer output voltage signal.

Grid Impedance Estimation via Excitation of $LCL$ -Filter Resonance

Abstract: Inverters adopted in distributed power generation, active filter, and uninterruptible power supply are often connected to the grid through an inductance-capacitor-inductance (LCL) filter. The impedance of the LCL filter has a typical frequency characteristic with a resonance peak. Hence, the LCL filter has to be damped in order to avoid instability. However, the resonance of the LCL filter can be also excited in a controlled way in order to individuate the resonance frequency in the spectrum (using for example the fast Fourier transform). This paper proposes to use a controlled excitation in measuring the grid impedance, since this one influences also the resonance frequency. This paper will address some possible limits, some solutions, and some implementation issues (e.g., how to obtain a controlled resonance in the filter without damaging the system) in order to use the resonant peak for grid impedance detection. The analysis is validated both by simulations and experimental results.