Tuesday, November 18, 2008
All objects exhibit electrical impedance. It is a measurement of the ability of the object to impede or oppose the flow of current when excited by a sinusoidal voltage. Electrical devices have impedance's that are composed of capacitive, inductive and resistive elements, which result in the impedance being complex and frequency dependent. A complex impedance exhibits a non zero phase shift between the current passing through it and the voltage across it.
Complex impedance determines the proper operation of electronic equipment and systems. Data and video cables should have the correct characteristic impedance or reflections will occur which will destroy the signal integrity. Generally, amplifiers should have a high input impedance and a low output impedance. Scope probes should present a high impedance, so that they do not load the circuit that they are testing. Batteries and power supplies should have a very low output impedance, so that they can deliver large output currents without collapsing the voltage.
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