Compatible Pepperl-Fuchs barriers with 1769-OF8C

This is partly related to PLC so here goes.

On the three panels to be tested, the AO channels are connected to KFD2-SCD2-Ex1. Problem is, the test unit at the other end of the barriers got nothing. After speaking with technical support of both P+F and Rockwell, it came down to the wiring on the AO card side. It is correct as per the P+F datasheet and 1769-OF8C installation manual. However, the card has the open wire bit set. Troubleshooting the wires reveal no open wire in themselves. But the impedance across the barrier inputs (#7 & #8) gave a impedance around 13.2 MOhms. So I disconnet from the barrier and wire direct to test unit. Got 4-20 mA perfect.

So the problem is the barrier. That for some reason don't work with this AO card. Anyone recommend an alternative P/N or brand in place of this? Thanks very much.

Are you sure that you're using terminals 7 & 8 and not 10 & 11 ?

More than once I've used the wrong layer of terminals on things like this. Duh.

It is 7 & 8. Top-most row.

Well, it's a standard Isolator.

If you want to use a different one, there are a fews questions:

Are you using it for Hazardous area Intrinsically Safe operation, or just isolation ?

Do you NEED Hart signals to pass across the isolator ?

And, not for nothing, did you try reversing the (+) and (-) input wires from the AO card to it ? There might be a diode inline internal.

Have you hooked a 4-20ma source Xmitter Simulator (in place of the AO card wires) to the input terminals and see that the isolator works?

Is the 24vdc supply to the isolator corect ? While this would not have anyting to do with open wire / high resistance, just one more item on the checklist.

I've used thousands of I.S. barriers and Isolators and can count only 2 that were DOA, and never a compatibility problem with I/O.

I'm just in a process of starting project with the same type of isolators. Only difference - it is 2-channels. p/n KFD2-SCD2-Ex2.LK. No problems at all. IS isolators work excelente. Did you power IS barriers with 24VDC source? (term. 14,15).

val_99 said:

Did you power IS barriers with 24VDC source? (term. 14,15).

Click to expand...

If I remember correctly, the KFD2-SCD2-Ex1 isolates the input, output, and power supply of the barrier from each other, and it needs 24VDC from the "Power Rail" or on the 14 & 15 terminals as mentioned by val99 if the output loop is not powered separately already.


So, I think if you throw 24VDC onto 14/15 to power your output loop it should work.

Kent

I put a 50ohm resistor in series with the test unit. Got 4-20mA.