The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 6 replies
  • Subscribers 31 subscribers
  • Views 1486 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

4-20ma Cabling - 3Wire

Les Spiteri
I have read many times about how it is beneficial to wire 4-20ma loops using twisted pair, however what if the wiring is 3 wire (i.e. +,- and signal)?
  • Does this mean that you simply use screened three core?

  • Does this mean you use two twisted pair and if so what one is the single?

Parents
  • 0
    The benefits of twisted pair are lost on a 3-wire loop device, as there are no two wires where the the currents are the same, but flow in opposite directions.


    3-core screened would be better.


    Basically, the current in the common wire should sum to the total current in the remaining power wire and the transmitter (signal) wire, so these three should be as close as possible and within the same cable.


    So, whilst 3-wire transmitters might be cheaper, they have their down-sides.
Reply
  • 0
    The benefits of twisted pair are lost on a 3-wire loop device, as there are no two wires where the the currents are the same, but flow in opposite directions.


    3-core screened would be better.


    Basically, the current in the common wire should sum to the total current in the remaining power wire and the transmitter (signal) wire, so these three should be as close as possible and within the same cable.


    So, whilst 3-wire transmitters might be cheaper, they have their down-sides.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines