SLC 500 4-20 mA output and pneumatic valve

Hi,
I send the value of 32767 the output which suppose to open the valve 100%, but it didn't. The old controller (Bailey) could open/close the valve with its 4-20 mA signal. What could be wrong here? Thanks for your help.

Bob

BobVuTo said:

What could be wrong here?
Bob

Click to expand...

There are a lot of possibiities! First, have you checked at the actuator to make sure you actually have 4-20 mA there? You should also check the voltage across the valve operator with the wires terminated at 4 and at 20 mA. Have you checked the wiring diagrams on both to make sure you don't have a ground loop? Are you sure that the Bailey and the PLC output are both self powered or both loop powered? Have you tried moving the valve using a simulator at the panel to make sure the wiring wasn't pulled loose? Have you verified that the PLC is actually giving you 20 mA?

I believe we need a little more information to answer this question correctly. (PLC Processor, Output Card, Your Wiring Diagram, etc.)

what catalog number output module are you using? ...

for many of them, 31208 is the magic number which will get you 20 mA (not 32767) ...

for 4 mA try 6242 ...

give us more information and we can probably offer more detailed help ...