PF700 analog out to 1771-ife/c

Hi all,
So I just converted an old dc drive and motor to a PF700 vector drive and vector motor. its all up and running except for the analog out to plc.
i have it set up to send drive current to the plc via 4-20Ma on analog output 1.
I am getting the signal to the plc but the signal is crosstalking to 3 other channels on the card giving me false readings on the card. pull one of the signal wires coming from the drive and the problem goes away.
do i need to tie drive 24vdc common to ground or something else like that?


The card is 1771-ife/c set up for differential current
the drive is 20BD052A3AYNAND0 ser. B, 480VAC, 52A, 40Hp
using pins 6 and 7 on drive for analog out 1
pram 340 bit 0 is set to 1
pram 342 is set to 2
pram 343 is set to 20Ma
pram 344 is set to 4Ma

any ideas would be great. this has a few of us stumped.

What you are describing, is called common mode noise when you read the manual for the IFE, and it appears to me, that the way to fix your problem is to buy a 4 to 20 ...4 to 20 isolator, Pheonix is popular in the US, here in NZ we use Intech isolators

hmm. I will see if I can find one and give it a shot. thanks

Sure enough! found an isolator around and installed and its working like a champ. thank you!