ABB Active analog problem

Aburke

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Join Date
Jul 2008
Location
melb
Posts
7
I am currently working on a job where i am recieving a 4-20ma signal from a tempreature controller. the signal is steady but the value in the plc is jumping around 10-15%

Processors tried, PM554 eco & pm573-eth
analog modules , AI561 & AX522

its only a problem with external sources, loop powered are ok.
i have tried everything i can think of!

I have used "statistic_real" to average it but its not ideal.

hooked the wires up to a SLC plc & was spot on so problem is back in the plc

its on both current & voltage inputs.

I have been using these plcs for around 4 years now & have only just stumbled across this issue.


Thanks in advance
 
Last edited:
My immediate reaction, too, was use an isolator, so I'm missing something.

>the signal is steady but the value in the plc is jumping around 10-15%

a) Does this mean that analog signal is steady when measured with a milliammeter, but the converted data values jump around?

>its only a problem with external sources, loop powered are ok.

>tried that (isolator?), not a noise problem.
>even with a calibrator it (the signal) jumps around

Let's confirm:

b) Loop powered current inputs do not jump around?

c) But a battery powered, "floating" calibrator the signal jumps around?

d) you've actually tried an isolator and it did not solve the problem?
further info:

d) Is the 24Vdc power supply used for supplying power to loop-powered instruments grounded one side or floating?
 
quote=danw;484693

My immediate reaction, too, was use an isolator, so I'm missing something.

>the signal is steady but the value in the plc is jumping around 10-15% Correct

a) Does this mean that analog signal is steady when measured with a milliammeter, but the converted data values jump around? Correct, we put a jumo logger in series & the 4-20 was steady. when the 2 wires are taken off the ABB & put on an allen bradely it is stable

>its only a problem with external sources, loop powered are ok.loop powered is perfect, thats what i have always used in the past

>tried that (isolator?), not a noise problem.
>even with a calibrator it (the signal) jumps around yep, both volatge & current

Let's confirm:

b) Loop powered current inputs do not jump around?no

c) But a battery powered, "floating" calibrator the signal jumps around?yes as does the feed back from the retransmission on temp controller

d) you've actually tried an isolator and it did not solve the problem?tried a phoenix contact 75hz isolator & also a current to voltage convertor. same problem.

further info:

d) Is the 24Vdc power supply used for supplying power to loop-powered instruments grounded one side or floating?
yes, i have used 3 diffent power supplies, 4 different processors (all ABB) and 2 different analog modules


still doing it.....
bugger!šŸ™ƒ
 
I don't know what a Phoenix Contact 75Hz module does, but the isolator Bryan recommends:
5kp06e.jpg

has a loop powered output like your other loop powered field devices so that it should work.

It isn't clear whether other loop powered devices are working with this particular rack/CPU/PS/AI combination or whether this is just a problem with the temp controller re-transmit.

If other loop powered devices are working OK, then using an isolator whose output is loop powered should work too.

But, if a battery powered calibrator is noisy, then that could be a sign that something else is amiss. I am stumped as to why a battery powered calibrator on the same AI card as loop powered devices is noisy when loop powered devices are not noisy.



It isn't clear whether one side of your DC power supply output is grounded (earthed) or not.
 
Hi, yeah might give that style a go!
Yes the 0v is earthed, also try joining all 0vs together.
Waiting on Abb to get back to me
We have another job which has 87 of these.... Already bought the components too
 
as you say yourself it is a problem with external, so do you connect the null of the power supply to the i- input and also to the ZP output of the abb.
in abb it is not allowed to have a external power source, so take the VP output for your sensors.
 
The sensor is an Ex I device so is going through a barrier. On the wiring diagram external voltage / current is ok
 

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