Distance from Current Transformer (CT) to digital readout meter

A CT is a current-mode device, if you have a closed circuit on the reade the only problem you might have is too large a voltage drop in the primary if the secondary leads are too small...

Where did you read about this problem?

If you use a 4-20 ma loop baring any electrical interferance you can run much longer than 70 feet. It depends on how much resistance the loop can stand before the supply voltage can not force 20 ma . Where I work we have hard telling how many loops like that using some 20 to 24 guage shielded wire.

The point you raise about voltage drop on the primary circuit is relevant, as a reason to consider using transducers. Although in practice a volt say, may be acceptable drop in most services. Keep in mind that the voltage seen by the primary is only about one twentieth of the secondary voltage for the 100/5 CT. You need to do the calculations and see if the design is suitable for the application.

The accuracy problem Kevin referred to relates to the VA rating of the CT, is the maximum VA that the CT can supply to the secondary load whilst retaining its stated accuracy. The CT secondary load includes the impedance of the ammeter plus connecting leads plus secondary CT reistance. If the secondary load impedance is too high then the CT iron saturates (partially or even fully) and the CT ratio ceases to be related to the turns ratio.

Peter Dettmann

Thanks, I have ordered 2 Solidyne CT-100 for Solidyne with a 4-20ma output and 2 digital meters from another company that will take a 4-20 ma input. Will replay back to this group/message when they are installed to let all know how they work. Again Thanks for the help.

I have installed the CT's but the company I order the panel meters from said they do not make a 4-20 ma input LED panel meter any more. Does any one know where I can get a 4-20 ma LED digital panel meter that is about 3 by 2 by 3 for around $20.00

Thanks Kevin