Can i get two 4-20ma output signals from one PTx
Can i get two 4-20ma output signals from one PTx
(OP)
Hi All
I have project where i need i require to take two 4-20ma signals.
1. 4-20ma to contorl valves
2. to connect to the PLC .
The transmitter is yokogawa pressure transmitter , loop -powered .
As i need one 4-20ma signal to control the exisiting control valves.
And if possible second 4-20ma signal DCS via PLC in order to alarm .
Thank You
I have project where i need i require to take two 4-20ma signals.
1. 4-20ma to contorl valves
2. to connect to the PLC .
The transmitter is yokogawa pressure transmitter , loop -powered .
As i need one 4-20ma signal to control the exisiting control valves.
And if possible second 4-20ma signal DCS via PLC in order to alarm .
Thank You





RE: Can i get two 4-20ma output signals from one PTx
Can you take the voltage from a dropping resistor across the input of the PLC and use the voltage? Yes.
Can you wire the 4-20mA in series with the PLC and the DCS? In all probability, yes.
Can you buy a signal multiplier, one 4-20mA in, two 4-20mA out and use it for getting a separate 4-20mA signal to the PLC and the DCS? yes.
something like Phoenix Contacts' MCR-FL-C-UI-2UI-DCI-NC
2814867
http://rd
RE: Can i get two 4-20ma output signals from one PTx
Roy
RE: Can i get two 4-20ma output signals from one PTx
There are two issues to watch out for:-
1. That the total loop resistance remains less than 600 Ohms.(which shouldn't be difficult)
2. Wire the PLC in the loop after the valve positioner. (PLC's often ground the negative terminal,this can cause issues if there is more than one mA input on the PLC). Placing the PLC last in the loop should over come this.
I trust this helps,
Mlv
http://www.coulton.com
RE: Can i get two 4-20ma output signals from one PTx
Roy
RE: Can i get two 4-20ma output signals from one PTx
I had assumed that we we talking in general terms about splitting a 4-20mA loop.
To implement this technique within a control loop the diagram would be modified as per the attached.
Thanks Roy for preventing further confusion.
I trust this helps,
Mlv
http://www.coulton.com
RE: Can i get two 4-20ma output signals from one PTx
I have often used a 1-5V PLC input across the controller 250 Ohm, that works as well.
BTW, I was refering to the original post, not your's, INSDE08 doesn't mention the controller, I think he has 2 (to) valves as well.
Regards
Roy
RE: Can i get two 4-20ma output signals from one PTx
RE: Can i get two 4-20ma output signals from one PTx
I have redesigned using your advises and ideas.
Cheers
RE: Can i get two 4-20ma output signals from one PTx
Bill
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