×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Control Logix/Powerflex analog input problems

Control Logix/Powerflex analog input problems

Control Logix/Powerflex analog input problems

(OP)
I have a control logix plc and two powerflex drives with speed and current feedback to the PLC (4-20ma).  24V is supplied from a common powersupply.

When I have any combination of 3 or more of the analog input signals connected all signals go crazy.  Signals work fine if less than 2 are connected.

Any ideas?

RE: Control Logix/Powerflex analog input problems

The drive's 0-10V analogue output -ve terminal is connected to chassis ground. Where is your 24v ground connected to? Are you creating unintended current paths through the ground connections when you connect multiple inputs?

----------------------------------

One day my ship will come in.
But with my luck, I'll be at the airport!

RE: Control Logix/Powerflex analog input problems

Just to add to what Scotty said, the cable shielding should only be grounded at one end, so as to prevent ground loops.

What about the size of 24v power supply?

RE: Control Logix/Powerflex analog input problems

Hello;
    Sounds like you may have a grounding issue between the two drives. One way to fix this is to use loop powered signal isolators.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources