INSTALLATION

Megablocks can be mounted vertically or horizontally using 35

mm DIN rail within a suitable enclosure, such as a field junction

box. Megablocks are removed from the DIN rail using a flat blade

screwdriver to release the mounting platform. Use of DIN rail end

stops is recommended to prevent sliding in vertical installations. The

four, eight, ten and twelve port Megablocks have labeling areas so

that segments can be easily identified according to plant standards.

MTL have a wide range of standard junction box designs for use with

Megablocks. See the data sheet for the range of Process JBs.

Shown above is an example of a common Fieldbus segment topology.

Twelve field devices are connected to a twelve-drop Megablock,

which is mounted in a field junction box. The trunk connector on

the Megablock is wired to the segment trunk cable that leads to the

control room or marshalling panel where the power supply and second

terminator are located. The example shows the

increased safety (Ex em) version connected to a general purpose

fieldbus power supply.

GROUNDING

To prevent ground loops, a fieldbus segment should only be grounded

at one point. This is usually done by grounding the cable shield at the

control room end of the segment. If a permanent segment ground

connection in the field is desired, this can be achieved by wiring

the shield terminal on one of the Megablock trunk connectors to a

suitable earth ground instead of wiring it to the shield terminal on the

Megablock Terminator.

Fieldbus Connection System (FCS) wiring blocks are protected by U.S.

Patents 6.366.437. 6.369.997 and 6.519.125.