Created Date: February 11,2000

Created by: Jeff Ashcraft

I have recently installed a DL205 with seven F2-02DA-1 installed. The problem I am having is with the output channels that are to be wired to our old MAX-1 controller file analog terminal board. With a field powerd loop into MAX one leg of the loop goes to SC(System Common) . The legs of the F2-02DA-1 output are +24vdc and -24vdc. Secondly some of the output channel 1's go to the MAX-1 terminal board directly and some of the second channels go to a multiplexer. The ones to the multiplexer work just fine. Is there a work-around for this problem?

Created Date: February 11,2000

Created by: Tom Jenkins

I had a little trouble following your wiring, but it appears you have a ground loop problem: your analog signals connect to ground in two places. The simplest solution is to use a signal isolator between the PLC and the controller. You can get these from lots of places (M-Systems, Action Instruments, A-Pi are some we have used) and they can be loop powered, 24 VDC powered, or 120 VAC powered depending on your needs.

Tom Jenkins

Created Date: February 12,2000

Created by: Mike McClanahan

Jeff,

We have had this problem with a lot of analog output systems including PLC Direct. The solution is that all devices connected to the analog output have to be isolated from each other. I wish they had designed the DA modules to be current sourcing so we could use common grounds (like most of the field equipment is) but... We eventually switched most of our equipment to DC voltage input or installed 4-20 ma loop isolators but the second is expensive and requires another piece of equipment to be PM'd for calibration.

Sorry I could not give you better news.

Mike