passing two 0-10 VDC signals in one four conductor shielded cable? 4

[PaulKraemer]

Hi,

I am working on a project in which I have to pass two separate 0-10 VDC signals between a PLC and a dedicated function controller. One of these 0-10 VDC signals is used to transmit a set point from the PLC to the dedicated function controller. The second 0-10 VDC signal is used to transmit the measured process value from the dedicated function controller to the PLC.

I am wondering if it would be safe to use a single four conductor shielded cable to pass these signals back and forth (using two conductors for each signal), or whether I should be concerned about these signals interfering with each other?

Any advice will be greatly appreciated. Thanks in advance.

Best regards,
Paul

 

[Compositepro]

There should be no concern of two 0-10VDC signals in adjacent wires interfering with each other. This would normally be done with three wires using a common zero reference wire. Shielding to exclude outside interference is good practice. It is important to avoid any ground loop currents in your signal wires.

 

[itsmoked]

I agree with Comp. Especially if neither signal is rapidly varying.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

CompositePro - use of a common return makes the assumption of a common ground at both ends. It also introduces the possibility of intermodulation of one signal onto the other due to IR drop in the common return. Depending on the accuracy involved it's possibly not worth the saving of one conductor. There are also disadvantages of running two separate grounds between two common points, so it's a design decision to work out which compromise is the least bad.

Is there any reason why 4-20mA can't be used, which addresses some of the problems noted above?

 

[PaulKraemer]

Hi ScottyUK, CompositePro, and Keith,

I just wanted to thank you for your help on this question, and I apologize for my delayed response. 0-10 VDC was my only option because the devices for which I am using these signals do not support 4-20 ma. It did cross my mind that I might be able to use a common return, but the device literature did not make it clear the the common terminal for the remote set point feature and the common terminal for the measured process value are internally connected. The terminals were labeled differently - one as "TEN RTN" and one as "GROUND". I figured I wouldn't take any chances and used a dedicated conductor for each. Anyway, it worked! Your responses gave me the confidence to give it a try. I appreciate your help!

Best regards,
Paul

 

[itsmoked]

I commend your choice. Just your time thinking about it was more expensive than the added wire.

Keith Cress
kcress -

http://www.flaminsystems.com