Topic
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.
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TL;DR: In this article, the authors measured the electrical conductivity of brass and stainless steel plates with 3 and 2% uncertainty (68% confidence level) by seeking the best fit (least-mean-square error) between experimental measurements of coil impedance and values calculated theoretically.
Abstract: Electrical conductivity of metal plates is measured by two distinct methods and the uncertainty associated with each method is evaluated. First, the impedance of an air-cored eddy-current coil is measured in the frequency range 100 Hz to 20 kHz. Corrections are made to account for the fact that the coil is not a pure inductor but exhibits finite resistance and capacitance in and between the windings. Then, the conductivity of brass and stainless steel plates is determined with 3 and 2% uncertainty (68% confidence level) by seeking the best fit (least-mean-square error) between experimental measurements of coil impedance and values calculated theoretically. The residual error in the fitting process is found to be the main indicator of uncertainty in the conductivity measurement. Second, four-point alternating current potential drop measurements are made on the same samples in the frequency range 1–100 Hz. Conductivity is determined from these measurements by means of a simple analytic formula, valid in a quasi-static regime, with an uncertainty approximately 0.5%. The main source of uncertainty in the four-point conductivity measurement is scatter in the voltage measurements. Both of these techniques give rise to smaller uncertainties in the measurement of conductivity than a MIZ-21A eddy-current instrument (2% and 40% for brass and stainless steel, respectively) and without the need for calibration specimens. In addition, the four-point approach is independent of magnetic permeability below a certain characteristic frequency and can be used to measure conductivity of ferrous metals. As an example, the conductivity of a spring steel plate is also determined.
124 citations
TL;DR: In this article, the authors presented linear sensors with two entries whose signals are influenced by both pressure and volume velocity, and classified them according to the way the volume velocity is determined or controlled.
124 citations
TL;DR: Finite-element simulations are used to calculate the impedance changes caused by cell growth on electrodes comparable in size to the cell to show that the impedance magnitude is expected to increase by at least 100% for partial cell coverage.
Abstract: Observation of impedance changes caused by cell growth on microelectrodes provides information about cell coverage and other important quantities, such as the cell-electrode gap. In this paper, we use finite-element simulations to calculate the impedance changes caused by cell growth on electrodes comparable in size to the cell. Parameters describing the impedance of the electrode without cells are derived from measurement. The results show that the impedance magnitude is expected to increase by at least 100% for partial cell coverage. We also report the frequency dependence of the magnitude and phase of the impedance and compare the simulation results with a lumped-element model. The simulation results are important for the design and modeling of arrays of cell-sized electrodes and also for the interpretation of experiments.
123 citations
TL;DR: Impedance analysis of AT and BT cut quartz of 5-and 6.19-MHz nominal frequencies under different conditions of operation is shown in this paper, where it is shown that inductance can be measured accurately and inductance calibration is preferable when resistance is large, surface structure can be studied by impedance analysis, inductance is a linear function of mass for elastic and viscoelastic films.
Abstract: Impedance analysis of AT and BT cut quartz of 5- and 6.19-MHz nominal frequencies under different conditions of operation is shown. Conditions are as follows: in air, in contact with a liquid, and simultaneous electrochemical deposition of viscoelastic layers in solution, Cu, Ag, poly(pyrrole tosylate), and poly(pyrrole tetrafluoroborate). Comparison with prevailing theories is included. It is shown that inductance can be measured accurately, that inductance calibration is preferable when resistance is large, that surface structure can be studied by impedance analysis, that inductance is a linear function of mass for elastic and viscoelastic films, and that the calibration range of EQCMs is extended by impedance analysis
123 citations
TL;DR: A grid impedance monitoring system for distributed power generation electronic interfaces that estimates the grid equivalent impedance and voltage source from the voltage measurements performed at the point of common coupling using a recursive least-squares algorithm implemented in the complex field.
Abstract: This paper proposes a grid impedance monitoring system for distributed power generation electronic interfaces. The system estimates the grid equivalent impedance and voltage source from the voltage measurements performed at the point of common coupling. The estimation algorithm is based on a recursive least-squares algorithm implemented in the complex field. Simultaneously, the system evaluates the quality of the estimation, minimizing its influence on the grid and detecting islanding situations. The proposed system performance has been evaluated under experimental testing.
123 citations