Ground question on an AD PLC and analog module

[bowang]

I have a problem using AD DL-05 (AC power, DC input and output) with an analog module F0-04AD-1. The PLC locks up itself once a while. The operator has to cycle the power to reset the PLC. The DC was designed floating. But recently I realized that the analog module internally short its current input – to the PLC G and LG. So DC and AC are grounded together. I suspect this is reason the PLC got locked up. I have a line filter for the AC before DC power supply and the PLC. Now I disconnected the G and LG from line ground to make both AC and DC floating. It seems to me that it is not right to leave the ground not connected for the PLC AC power. But it works fine so far. Is there anybody who can tell me if this is right way to do it? Or any other recommendation to solve my problem?

 

[Tark]

I haven't used the DL-05AD models, just the DL-05AA models. I do remember using the analog module and having to remove the ground jumper between G and LG. I think I connected G to ground, although I can't be sure. Might check with AD to make sure.

 

[elevmike]

What do you mean by "locks up"? Does the program stop running, or does the analog module stop updating? Do you have one side (-) of your DC power supply grounded? Are you using a seperate power supply for the current loop? What the min current? (Is the jumper set properly?) Does the transmitters spec/match the the loop resistance?

It's hard to answer your question. Your discribing a strange problem. Provide more detail and maybe we can give it a try.

Also very carfully re-read Chapter 3, (3-4 & 3-5) of your Analog Module manual.

 

[darrenj]

Do you have one side (-) of your DC power supply grounded?

Mike..he refered to his DC supply as "floating" that usualy means the - is not grounded..He also said he cut the jumper on his AC side, That now means his AC side is floating..

From a code point of view an AC supply isnt allowed to float unless it is a class 2 transformer (Current limiting)..I do not know if there are any "codes" on the DC side..Good practace says ground them but i dont think you have to..

Also check your wiring..is the signal side "shielded"..do you have the "drain" at one end?..etc etc..

D

 

[AndyT]

Bowang,
If I understand this correctly you left the LG and G jumper connected on the 05 terminal strip and just removed the ground from the system. If this is correct please try removing the jumper between the two grounds on the terminal strip and connect the ground to the AC side. When trying to float the DC side this is a common recommendation from Tech Support.

 

[bowang]

Thank you, everybody. I did leave the jumper for G and LG connected. I am going to do what Tark and AndyT said. Remove the jumper, ground AC side. This will do what I was looking for, to have DC floating and AC grounded. I may have to wait for a couple of weeks to find out if the PLC stops running again.