What is impedance?

Impedance is measured in Ohms and represents the total resistance that the cable presents to the electrical current passing through it. Impedance is associated with AC circuits.

At low frequencies the impedance is largely a function of the conductor size (resistance), but at high frequencies, conductor size, insulation material and insulation thickness all affect the cable's impedance. Matching impedance is very important, for example, if the system is designed to be 100 Ohms, then the cable should match that impedance, otherwise error-producing reflections are created at the impedance mismatch, seen as lower return loss in bidirectional signal cables.

The symbol for Impedance is Z.

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