4 Wire Voltage Output

bodoo23

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Join Date
Jan 2018
Location
Athens
Posts
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I am using a siemens output module and I saw that there is also 4 wire diagram for voltage output.

Is there anyone who can explain the reason of 4 wire insted of 2 for voltage output ?

Thanks in advance.
 
It could be for voltage drop compensation. I can't remember exactly but it may measure on one set and use that to adjust. I may be completely wrong but seems to ring a bell. I may be confusing it with a process transmitter
 
But the OP is asking about a 120v output.

I read only "voltage output" and since it's about the difference between 2 or 4 wire I assume it's about an analog voltage output like 0..10V

I think what SD_Scott posted is about what OP asked.

Still it is not entirely clear to me why to use 4 wire. is it to overcome and detect things like wire break?
 
I read only "voltage output" and since it's about the difference between 2 or 4 wire I assume it's about an analog voltage output like 0..10V

I think what SD_Scott posted is about what OP asked.

Still it is not entirely clear to me why to use 4 wire. is it to overcome and detect things like wire break?

In a current loop the current stays the same as long as the loop doesn't exceed a certain impedance. In a voltage loop the transmitter needs to compensate for the lead resistance and in a 4 wire setup it can compensate for lead wire imbalances also. Not sure what OPs output card is though. Hope that helps.
 
In a current loop the current stays the same as long as the loop doesn't exceed a certain impedance. In a voltage loop the transmitter needs to compensate for the lead resistance and in a 4 wire setup it can compensate for lead wire imbalances also. Not sure what OPs output card is though. Hope that helps.

thanks.
the siemens card can probably be set-up either as 2 or 4 wired and from my mind also voltage or mA can be chosen
 

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