Spur isolation in a fieldbus network

A device coupler capable of connecting a plurality of field devices to a network trunk of a two-wire fieldbus network of the type that transmits data signals and power over the two wires, the device coupler comprising:

• a trunk interface for connecting the device coupler to the network trunk and two or more spur isolation sets connected to the trunk interface in parallel with one another;
• each spur isolation set comprising:
• an isolating element connected to the trunk interface and a set of two or more spur interfaces connected to the isolating element, the spur interfaces being connected in parallel with one another to the isolating element, the isolating element connecting the trunk interface and the spur interfaces together and galvanically isolating the trunk interface from the spur interfaces;
• the two or more spur isolation sets comprises a first spur isolation set and a second isolation set;
• the plurality of spur interfaces of the first spur isolation set is galvanically isolated from the plurality of spur interfaces of the second spur isolation set by at least the isolating elements of the first and second spur isolation sets;
• and
• the isolating element of each of the two or more spur isolation sets is a transformer whereby the plurality of spur interfaces of the first spur isolation set is galvanically isolated from the plurality of spur interfaces of the second spur isolation set by at least the transformers of the first and second spur isolation sets.

A method of connecting a plurality of outputs to an input for transmission between input and outputs, the input being adapted for connection to a network trunk of a two-wire fieldbus network that transmits data signals and power for field devices over the two wires, the outputs being adapted for connection of field devices, the method comprising the step of:

• dividing all of the plurality of outputs into two or more sets of outputs, each output being in one and only one set of the two or more sets of outputs, each set of outputs including two or more outputs;
• and
• connecting two or more transformers in parallel with one another to the input and connecting the two or more transformers to the sets of outputs, each set of outputs being connected in parallel with one and only one respective transformer, the respective transformer connecting the set of outputs to the input and galvanically isolating the set of outputs and the input;
• whereby each set of outputs are galvanically isolated from the network trunk and from the other sets of outputs when the input is connected to the network trunk.