test a current output 1762-OF4

Narlin

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I have and OF4 configured for 4-20mA. How can I test the current output from a 1762-OF4 on the lab bench. i.e. the OF4 does not have a load attached. Just putting a ammeter between COM and “I out 0” does not work. I tried using a 100 ohm resistor as a load, but that didn’t work either? The manual says “Resistive load on current output can be 0 to 500 ohms. What can I use to simulate a load? I am pretty sure that the card is OK. I tried it as voltage output (configured accordingly) and it worked perfectly.


narlin
 
Narlin,

You should be good with a multi-meter set to mA...that's all we do to test our Analogue output cards. Have you checked the 2 x dip sw's in the top of the card? They are set to CURRENT by default.

Post a shot of your card config...it may be something simple that's ticked/not ticked!

Regards,

Rob
 
I would have said there were dip switches in the top of that card too! but i don't find any and the mnaual doesn't mention any. Maybe we are remembering the IF2. this is an OF2
 
D'oh!! 🙃 You're absolutely right Narlin! Sorry for that!

Config looks good...what meter are you using? What does it display when you try writing a value to the particular channel under test? 0mA/4mA or something else?

Rob
 
OK. Part of the problem was the meter. I grabbed another one that is ancient, but works just fine (tested just now on a current source that has a load attached).

New issue: The OF4 is putting out way too much current. About 100 mA? WTF? Also, it isn't adjustable. It is connected to slot 5 of a ML-1400. Using O:5.0, i can change the ouput counts from 0 to 16380. However, current is too big and steady.
 
I just tested a different channel of the OF4, and i get the same odd behavior. Output is about 125 mA? It varies by a few mA (< 10) when i run the counts from 0 to 16380. i am going to check the V output again. 1st have to change the config and wiring?
 
Narlin,

Your screen shot shows you have it configured for 'Raw/Proportional' so the data values (i think) should be 6241/31206 = 4/20mA. This should have no bearing on your problem, but should confirm the cards correct operation when you have the problem sorted.

What wiring are you changing?? Can you not remove all external wiring and just test channel outputs direct at terminal?

Rob
 
This time i have not changed wiring. One wire goes from card COM to meter COM. THe other wire (only 2) goes from card O:5.1 (that was a change) to meter mA input. And meter is now set to 0 to 30 mA. I have found that there is a linear response to counts, when the output counts at O:5.1 are in the range of 0 to 900 counts. Yes, it should be 0 to 32760, and when i was complaining about too much current, it was that. By and by, the linear output range seems to be 0 to about 21 mA. That would be fine with me if the counts were correct. Surely i have some configuration messed up somewhere. But where?
 
!!!!!!!!!!!!! Got it. Was mis reading the Current and voltage inputs on the card. Straigtened that out, used a working mA meter and voila. Correct results.

Thanks for your patience.

narlin
 
Narlin,

Glad you got it sorted! Did you mean 'outputs' on the card not inputs? Are you getting 4-20mA at 6241-31206 now?


Rob
 
yes and yes. Now i am just refining the OIT input to take advantage of the resolution. I had it set as 0 to 100 in integer and the PLC multiplying by 327.6 to get my counts sent to the OF4.

I am still multiplying by 327.6, but i am letting the OIT use 0.00 to 100.00 as values.
 
Oops! 0 x 327.6 = 0. It should = ~6241. I'll work on that. Not an issue but thanks for the observation.
 
I wasn't using an SCP for this, but that might make the math easy (as in A-B does it for me).
 
Can save a lot of programming time, and makes setting up your analogue(s) a lot quicker (in my opinion!) :)



Sounds like you're almost good to go!


Rob
 

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