MicroLogix 1762-OF4

[Ones_Zeros]

Hey guys I 'm having problems getting a valve to move that has a DVC6200 actuator connected to it via a MicroLogix 1762-OF4 PLC card.
I can move the valve with a 789 process meter at the valve or on the same wires before connecting them to the PLC.

Here is a pic of the DVC6200 actuator that I'm wiring the PLC to. It shows how the DVC6200 should be wired to the PLC.

I have change the PLC 1762-OF4 card to test to make sure the card was good.

What would you guys recommend first?
1. I have supplied 24v loop power.
2. My thought was if I can move it with the meter then I should be able to connect the wires to the PLC and type in a valve on the output to move the valve.
3. Can you guys give me some advise/direction on how the wiring should be just so I can double check myself?

I appreciate the help!
Thanks

 

[Mickey]

Have you put a meter in series with the output card to monitor the actual ma from it while connected to the position transmitter?

 

[Mickey]

Also.. I saw this from the manuals you might want to take a closer look at this.

From position Transmitter manual:
Input Impedance The input impedance of the DVC6200 active electronic circuit is not purely resistive. For comparison to resistive load specifications, an equivalent impedance of 550 ohms may be used. This value corresponds to 11V @ 20 mA.


From analog output card manual:
8 Analog Output Module Publication 1762-IN016D-EN-P - Resistive load on current output 0…500 Ω (includes wire resistance)

 

[danw]

I think Mickey found the issue. The handheld loop current simulator voltage source is stiffer than the analog output card and so it can drive the positioner's load impedance.

You'll need a 4-20mA isolator, not for its isolation capability but for its ability to drive current through a higher load impedance.

Something like the API 4300 whose spec is:
"20 V compliance, 1000 Ω at 20 mA"

https://api-usa.com/pdf/api/api4300g-4310g.pdf

Or a different AO card.

 

[Ones_Zeros]

Just so I understand, You think the 1762-OF4 output PLC card I have doesn't have enough current to drive through higher load impedance of the DVC6200 (550 ohms)?

Which would be a better choice?
use a different PLC card, if so which one would you recommend for this application or should I get the 4-20mA isolator?


thanks again for all your help with this issue

 

[Mickey]

I don't think they make an output card (1762 series) that supports more then 500 ohms. ( check it out)

I would go with an isolator.

another source..

https://cdn.automationdirect.com/static/specs/fcsignalconditioners.pdf

Have you checked the ma output with and then without the DVC6200 connected?

A simple test can prove it. Do you have a 500 ohm resistor laying around?

 

[Ones_Zeros]

Mickey
I had a test PLC panel that I used on the DVC6200.
its a CompactLogix PLC that had a 1769-OF4CI output card. The documentation says that it has a (Output Impedance >1 MΩ)
The output card was wired up identically to the other PLC output card.

I was then successfully able to move the valve and receive feedback from the test 1769-OF4CI card.

I'm by no means a PLC expert, I'm learning everyday, but I have to say that I have never experienced this to were the PLC output card didn't have enough output current to drive through a high load impedance to move a valve.

I really appreciate your patience and everyone that helped me on this issue. I learned a lot from this issue.

Thanks Again

 

[Mickey]

Glad you solved your problem.

HMMM? I am not sure what the spec "output impedance means" but glad it worked.
Someone please jump in.

From manual of the 1769-OF4CI:

Resistive Load on Current
Output
0 to 500 ohms (includes wire resistance)

Output Impedance >1 M ohm

And thanks for letting the forum know the outcome.

I am still curious, did you test the 1762-OF4 card with a lower load?

 

[Mickey]

A little research tells me the "output impedance" spec. is the internal impedance of the output card. Not the load capability. You would have to have a lot of voltage to drive through a load >1 M ohm . No analog card can do that.

If the 1769 series card worked the 1762 series card should also work.

More testing...

 

[Ones_Zeros]

Ok thanks for the feedback
I will do some further testing on the
1762 series card


Can you help explain why that if both PLC cards 1762-OF4 and the 1769-OF4CI output cards have (Resistive Load on Current
Output - 0 to 500 ohms (includes wire resistance) then how is that I can move the valve with the 1769 series card and not the 1762 series card?

Is there any jumpers on this 1762-OF4 output card that would be
disabling the card or output?
The two series cards are physically wired the same, that leads to think there might be a setting or dip switch that has to be enabled on the 1762 card.



Oh..also I didn’t test the 1762-OF4 with a lower load yet.
To do this is all I do is install a 500 ohm resister in series with the
Output card? Just wanted to make I do it correctly.


Thanks again

 

[Mickey]

Hard to trouble shoot from afar. Can you post the .rss file zip it first.


No dip switch that I am aware of.

Check and double check the bus connector.

Your test resistor can be 500 ohms or lower. Or just connect your meter up to it, don't need a resistor. This at least tells you the card is alive.

 

[Mickey]

Mickey
I will PM you the .rss file if thats OK?

I will also check

Maybe you can look it over to see if there is any settings that I have wrong.

Sure, check your PM.

 

[Ones_Zeros]

OK I'll check..Thanks

I haven't received PM yet

 

[Mickey]

Looks like it should work to me.

Does the other channel(s) work?

 

[Ones_Zeros]

Yeah all other channels work fine