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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07 Nov 2002
TL;DR: In this paper, the authors developed an rf circuit model for single walled carbon nanotubes for both dc and capacitively contacted geometries, and calculated the complex, frequency dependent impedance for a variety of measurement geometry.
Abstract: We develop an rf circuit model for single walled carbon nanotubes for both dc and capacitively contacted geometries. By modeling the nanotube as a nano-transmission line with distributed kinetic and magnetic inductance as well as distributed quantum and electrostatic capacitance, we calculate the complex, frequency dependent impedance for a variety of measurement geometries. Exciting voltage waves on the nano-transmission line is equivalent to directly exciting the yet-to-be observed one dimensional plasmons, the low energy excitation of a Luttinger liquid.
97 citations
TL;DR: In this paper, a series of experiments are performed to assess the validity of an equivalent circuit model of ionic polymer transducers, where the fundamental parameters of the model are the dielectric permittivity of the material, the viscoelastic modulus, and the effective strain coefficient of the transducers.
Abstract: A series of experiments are performed to assess the validity of an equivalent circuit model of ionic polymer transducers. The fundamental parameters of the model are the dielectric permittivity of the material, the viscoelastic modulus, and the effective strain coefficient of the transducer. The results demonstrate the validity of a simplifying assumption regarding the reflected impedance of the polymer. This allows us to use a simpler set of expressions to predict the time and frequency response of the polymer. The expressions for sensing and actuation are verified in a series of step response and frequency response tests of cantilevered transducers. The curvefit algorithm used for parameter identification works well but there is always a tradeoff in accuracy between the time domain and frequency domain measurements. This could imply the existence of an input-level dependence on the parameters. In spite of this level dependence, the linear model is able to predict the response of an input-output pair tha...
97 citations
TL;DR: In this paper, a modified slot discharge detection method, which permits tests without shutting down the machine or using auxilliary high-voltage test equipment, was investigated, which involves connection of frequency sensitive equipment across all or part of the ntral impedance.
Abstract: A modified slot discharge detection method, which permits tests without Shutting down the machine or using auxilliary high-voltage test equipment, was investigated. The method involves connection of frequency sensitive equipment across all or part of the ntral impedance. Tests on eight vertical water wheel generators in the range of 20,000- to 40,000-kva capacity indicate that the method is generally applicable when there is a current transformer or some other impedance in the generator neutral.
97 citations
01 Nov 1995
TL;DR: An asymmetrical and sensitive magneto-impedance effect was realized in twisted FeCoSiB and CoSiB amorphous wires magnetized with a dc-biased ac current, in impedance up to about 120% as discussed by the authors.
Abstract: An asymmetrical and sensitive magneto-impedance effect was realized in twisted FeCoSiB and CoSiB amorphous wires magnetized with a dc-biased ac current, in impedance up to about 120%/Oe The asymmetrical magneto-impedance (AMI) is useful to construct linear field sensors without any dc bias field Mechanisms of the AMI are also discussed
97 citations
Patent•
04 Dec 1990TL;DR: In this paper, a variable capacitance circuit comprising a capacitor array, associated switching elements and transient impedance varying circuits is proposed to change and adjust the frequency of the crystal oscillator.
Abstract: A variable capacitance circuit comprising a capacitor array, associated switching elements and transient impedance varying circuits. The capacitor array comprises a plurality of capacitor elements connected to a common node coupled to a crystal oscillator in a crystal oscillator portion and each capacitor element includes a connected switching element that controls activation of selected capacitor elements that are selectively placed in operation as load capacitance with the crystal oscillator to change and adjust its frequency. Further, circuits are provided in a temperature compensation portion to selectively control the activation of the switching elements based upon decoded compensating values provided in memory, such as based upon sensed oscillator temperature conditions. The transient impedance varying circuits comprise multi-level voltage generating circuits for changing the continuity impedance of activated switching elements, among switching elements being switched, to another impedance level or one of a plurality of additional impedance levels. As a result, an intermediate impedance value can be created between the ON and OFF states of the switching elements so that there is no rapid change in the total equivalent capacitance imposed by the capacitor array on the oscillator resulting in smooth capacitance switching which corresponds to smoother frequency adjustment of oscillator output.
97 citations