adccommunitymod (AutomationDirect) asked a question.
Simple question on current loops
Created Date: October 19,2011
Created By: DetroitSound
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Can I put multiple devices in series on a 0-20ma current loop? Also, can I use a standard toggle switch to bypass one of them if it is not being used? I have a machine with an ABB ACS600 drive and one of the 0-20ma outputs has failed.
Created Date: October 19,2011
Created by: Bob S BN
My $.02,
Each device that is monitoring (plc inputs, drive inputs, etc..) the current loop will have some resistance involved with it.
The outputting device will have to increase voltage accordingly to maintain the proper current level in the loop.
At some point there will be a maximum voltage the outputting device can handle.
Perhaps oversimplified, but you will need to look at each device in the loop and do the math to see if you are overloading the output.
Hope this makes sense, and helps,
Created Date: October 19,2011
Created by: DetroitSound
My $.02,
Each device that is monitoring (plc inputs, drive inputs, etc..) the current loop will have some resistance involved with it.
The outputting device will have to increase voltage accordingly to maintain the proper current level in the loop.
At some point there will be a maximum voltage the outputting device can handle.
Perhaps oversimplified, but you will need to look at each device in the loop and do the math to see if you are overloading the output.
Hope this makes sense, and helps,
Actually that was what I guessed. That since it is a current output, rather than voltage, the outputting device will attempt to maintain the stated current level, taking Ohm's law into account, i.e. if there is too much resistance for the available voltage it will not be able to maintain that current.
Thank you very much!
Created Date: October 19,2011
Created by: Bob S BN
taking Ohm's law into account
Ya, not many exceptions to THAT rule:D
Created Date: October 20,2011
Created by: bcarlton
Some devices must have the circuit low end as one part of the signal (like most Direct Logic types). Only one of these may be used. The others must be isolated inputs to be used in the middle of the line.
Created Date: October 19,2011
Created by: DetroitSound
Can I put multiple devices in series on a 0-20ma current loop? Also, can I use a standard toggle switch to bypass one of them if it is not being used? I have a machine with an ABB ACS600 drive and one of the 0-20ma outputs has failed.