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How to Measure the Inductance of a Twisted Pair Cable

Twisted pair cable, once the mainstay of landline telephone applications, has become a popular choice in the design and implementation of local area networks -- or LANs. The pairing of wires provides a means for sending and receiving signals, while the twisting of wires cancels out electromagnetic interference. Measuring the inductance of twisted pair cable requires knowledge of the manufacturer's specifications for the cable, which will serve as inputs to an equation that will render the cable's inductance.

Things You'll Need

Cable specifications

Instructions

- 1
  Find the manufacturer's specifications for the cable you want to measure. Look up the values for the diameter of each wire in the pair, the distance between each wire and the length of the cable.
- 2
  Multiply the separation between the two wires by 2, and divide by the diameter of the wire. Multiply this by 10 to the negative ninth, then multiply this by 10.16. The actual equation looks like this, where L = inductance in nanohenry-inches, ln = length, d = diameter and s = the separation between the wire:
  L(twisted pair) = 10.16*10^-9*ln[2s/d]
- 3
  Measuring the inductance of twisted pair cable can also be accomplished by determining the category of the cable you wish to measure. The most common application of twisted pair cable is in LAN networks. Twisted pair cable comes in six categories, with category 5 the most commonly used in LANs. The inductance of category 5 twisted pair is 525 nanohenry/meters

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