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.

Digitally controlled element sizing

Abstract: Effective control of impedance values in integrated circuit applications is achieved with an integrated circuit transistor whose size is digitally controlled. The digitally controlled size is achieved, for example, with a parallel interconnection of MOS transistors. In one application, the digitally controlled transistor serves as a controlled impedance connected to an output terminal of an integrated circuit. In that application, a number of transistors are enabled with control signals, and the collection of enabled transistors is responsive to the input signal that normally is applied to a conventional transistor. In another application, where the digitally controlled transistor serves as a controlled impedance at the input of a circuit, only the control signals that enable transistors and thereby determine the effective developed impedance are employed. In still another application, the digital control of the transistor's size is employed to control the speed or power consumption of the effective transistor. Such control is exercised to erase the manufacturing variability of the integrated circuit. Alternatively, such control is exercised as part of a feedback control of the operational characteristics of the entire circuit. In the feedback control application, the digital signals that control the transistor's size are obtained from an assessment of the circuit's operation. In the manufacturing variability control application, the digital signals that control the transistor's size are obtained from a measure of the integrated circuit's parameters relative to a reference element.

Structural impedance based damage diagnosis by piezo‐transducers

Abstract: Although structural mechanical impedance is a direct representation of the structural parameters, its measurement is difficult at high frequencies owing to practical considerations This paper presents a new method of damage diagnosis by means of changes in the structural mechanical impedance at high frequencies The mechanical impedance is extracted from the electro-mechanical admittance signatures of piezoelectric-ceramic (PZT) patches surface bonded to the structure using the electro-mechanical impedance (EMI) technique The main feature of the newly developed approach is that both the real as well as the imaginary component of the admittance signature is used in damage quantification A complex damage metric is proposed to quantify damage parametrically based on the extracted structural parameters, ie the equivalent single degree of freedom (SDOF) stiffness, the mass, and the damping associated with the drive point of the PZT patch The proposed scheme eliminates the need for any a priori information about the phenomenological nature of the structure or any ‘model’ of the structural system As proof of concept, the paper reports a damage diagnosis study conducted on a model reinforced concrete (RC) frame subjected to base vibrations on a shaking table The proposed methodology was found to perform better than the existing damage quantification approaches, ie the low-frequency vibration methods as well as the traditional raw-signature based damage quantification in the EMI technique Copyright © 2003 John Wiley & Sons, Ltd

Method and apparatus for measuring complex impedance of cells and batteries

Abstract: A periodic time-varying current with smallest period 1/f1 excites a cell/battery (10) and provides a timing reference. Linear circuitry (35, 55) produces two signals, one proportional to the excitation current, the other proportional to the responding time-varying voltage. These signals are processed with identical frequency-limiting filters (40, 60) to attenuate higher-order harmonics and noise. Using the timing reference for synchronization, a microprocessor/microcontroller (20) commands analog to digital converters (45, 65) to sample the frequency-limited current and voltage signals at equally-space times over a period and accepts the digitized samples as inputs. The digital samples are averaged over multiple periods and employed to calculate averaged Fourier coefficients of in-phase and quadrature components of frequency-limited current and voltage at frequency f1. By numerically combining these Fourier coefficients, the microprocessor/microcontroller (20) determines real and imaginary parts of the cell/battery's (10) complex impedance at frequency f1.

Noise Resistance Applied to Corrosion Measurements I. Theoretical Analysis

Abstract: The measurement of current and voltage fluctuations on the same electrochemical cell allows the evaluation of a quantity R{sub n} known as noise resistance, which has been proposed as an indication of the corrosion resistance of the material under study The theoretical basis for the relationship between R{sub n} and the electrode impedance Z is developed, taking into account the various measurement schemes currently in use Parameters such as cell geometry, solution resistance, and electrodes with different kinetics are considered It is shown that, in general, the modulus of the electrode impedance can be derived by measuring the power spectral densities (PSD) of the voltage and current noises The circumstances in which R{sub n} is equal to the polarization resistance of the electrode are also discussed