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Bioelectrical impedance analysis (BIA) is a method for estimating body composition, in particular body fat and muscle mass, where a weak electric current flows through the body, and the voltage is measured in order to calculate impedance (resistance and reactance) of the body. Most body water is stored in muscle.
Standard bioelectrical impedance analysis (BIA), like EIM, also employs a weak, high frequency electric current to measure characteristics of the human body. In standard BIA, unlike EIM, electric current is passed between electrodes placed on the hands and feet, and the impedance characteristics of the entire current path are measured.
The amplitude of the wave is proportional to the measuring potential difference at the frequency of the vibration, efficiently filtered by a lock-in amplifier that boosts probe's sensitivity. [41] [61] [62] The vibrating ion-selective microelectrode was first used in 1990 to measure calcium fluxes in various cells and tissues. [63]
Metal electrodes are made of various types of metals, typically silicon, platinum, and tungsten. They "resemble a leaky electrolytic capacitor, having a very high low-frequency impedance and low high-frequency impedance". [30] They are more suitable for measurement of extracellular action potentials, although glass micropipettes can also be used.
Impedance analyzers are a class of instruments which measure complex electrical impedance as a function of frequency. This involves the phase sensitive measurement of current and voltage applied to a device under test while the measurement frequency is varied over the course of the measurement. Key specifications of an impedance analyzer are ...
Focused Impedance Measurement (FIM) is a recent technique for quantifying the electrical resistance in tissues of the human body with improved zone localization compared to conventional methods. This method was proposed and developed by Department of Biomedical Physics and Technology of University of Dhaka under the supervision of Prof ...
The electrometer changes this "high impedance signal" to a "low impedance signal" by using a voltage follower circuit. A voltage follower reads the voltage on the input (caused by a small current through a big resistor). It then instructs a parallel circuit that has a large current source behind it (the electrical mains) and adjusts the ...
The term biosignal is often used to refer to bioelectrical signals, but it may refer to both electrical and non-electrical signals. The usual understanding is to refer only to time-varying signals, although spatial parameter variations (e.g. the nucleotide sequence determining the genetic code) are sometimes subsumed as well.
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