Foundation Fieldbus Connector

[rodneysab]

Foundation fieldbus Connectors have 4 pins but only 2 are necessary. What are the other 2 for? Our contractor claims connectos with only 2 pins are suitable, where can I base his allegations on?

 

[djs]

I believe that Foundation Fieldbus H1 is a two wire interface. The two wires carry both 24 VDC for device power and also the communications signal.
I was not aware that there is/was a "standard" connector for FF H1.

 

[rodneysab]

Actually I mean not the H1 but the spur segment.

 

[djs]

FF H1 is the fieldbus that uses 24VDC with Manchester encoding for the data. They have another, newer fieldbus that is ethernet based.

So your "spur" lines are also H1.

 

[rodneysab]

Ok in this case only two pins are really necessary. But why are there connectors with 4 pins? So far I haven´t got any reasonable explanation.
Thanks anyway.

 

[djs]

You are probably talking about the M12 type connectors. These are a standard, general purpose connector that is reasonably water proof. Used quite frequently in Europe. For some reason seems to have become widely used with FF H1 and also Profibus-PA. Both of those fieldbusses use the same electrical interface. So one answer is legacy and history.

 

[danw2]

Note that all three Foundation Fieldbus connectors, whether M12 or 7/8" 4 pole connectors, use only one pair of signal wires and a shield wire:

ABB 7/8" pinout

Turck 7/8" pinout

Turck M12 pinout

 

[rodneysab]

Thanks to djs and danw2.