Distance from Current Transformer (CT) to digital readout meter

Help,

I would like to install a CT on an electrical service and connect it to
a digital readout display (with a 5 amp input) 70 feet away using #14
gage wires. The CT would have a primary of 100 amps and a secondary of
5 amps (100:5). From what I have been reading is that I will not get a
correct readout at the display because of the distance of the wire.

My question is that if I use a CT that has an output of 4-20ma and a
digital readout with a 4-20ma input, Will I still get an incorrect
reading at the display do to the distance.

Thanks in Advance
Kevin

 

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