SCP error RSLogix 500?

bright676

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Join Date
Nov 2012
Location
va
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494
When using 4 to 20mA I have been using 3277 to 16384 for the input min and max.

We had new controls put in for a machine several years ago and for the actual drive current amp SCP they are using;
input min 3277.0
input max 16383.0 SHOULD THIS BE 16384.0?
scaled min 0.0
scaled max 50.0

Ever since the install several years ago there have nuisance alarms for high amps.
On the VFD for amps it is pulling 6.7 amps but the panelview plus is showing 8.0 and up. Could the last digit difference on the input max be causing this error?

Thank you
 
You are talking about 1 part in a range of 13107 counts, so it can only cause a very tiny error in the result.

I would look closely at the scaling parameters in the VFD and make sure that it is set up for 4 to 20mA (not 0 to 20mA) and that the 20mA value is set up equal to 50 amps and not something else. And make sure that the analog signal from the VFD is assigned to output current.
 
Thank you for the reply, I will put and actual amp meter on the motor myself tonight to see what it actually is, and which display is wrong.
 
Last edited:
Also tell us the catalog number of your analog card.

And how it's configured. Or post the program (if you can) the .RSS file for your PLC. Zip it first.
 
I wont be able to post the whole program because of work rules, but I will post the rungs in question.
 
Thank you for the reply, I will put and actual amp meter on the motor myself tonight to see what it actually is, and which display is wrong.

Your ammeter may not be a good way to tell actual motor current. If the VFD is in good working condition, the reading on its display should be more accurate and will match what it is trying to send to the analog pins.

https://www.youtube.com/watch?v=5ZHqNW69eCw

EDIT: And the video basically proved me wrong...oh well, it is interesting to see a real test.
 
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