Pepperl+Fuchs Blog

Remote I/O—Getting on Board the Bus to Better Communication

Posted by Patricia Stafford on Wed, Apr 08, 2015

What is remote I/O?

Remote I/O refers to a remote input/output system that transfers data from analog to digital form so that field devices can communicate with a network.

Types of remote I/O include LB and FB. Both LB and FB perform the same function. The difference between them is the type of hazardous environment and methods of protection each one is rated for. LB remote I/O is rated for mounting in Zone 2 and 22, Div. 2 with intrinsic safety protection methods Ex ia, Ex ib, and Ex ic. FB remote I/O is rated for mounting in Zone 1 and 21 with intrinsic safety protection methods Ex ia and Ex ib.


What are the components in a remote I/O system?

A basic remote I/O system consists of a backplane, communication interface, power supply, I/O modules, and terminal blocks.

  • Backplane — What exactly is a backplane? A backplane looks like a big green circuit board (LB) or black cabinet (FB), and you connect I/O modules to it by inserting the modules into the slots.
  • Communication interface — Also known as a bus coupler, com unit, or gateway, the communication interface serves as a gatherer, translator, and compiler of information.
  • Power supply — The power supply is 24 VDC for the modules and communication interfaces.
  • I/O modules — I/O modules are barriers that carry input/output data from the field devices.
  • Terminal blocks — A terminal block is where wires are connected. One terminal block is required for each barrier.

What kind of analog devices can I connect to remote I/O?

You can connect 4 mA … 20 mA devices to remote I/O, including water flow meters, valve positioners, pressure transducers, temperature transmitters, as well as other kinds of devices, such as thermocouples, resistance temperature detectors (RTDs), mechanical contacts, and visual or audible alarms.

What is the principle behind remote I/O?  How does it work?

Remote I/O works by converting all standard inputs and outputs from analog to digital, allowing data to be converted to a different, more advanced network protocol.

Remote I/O is compatible with the following network protocols:

  • Modbus RTU
  • Modbus TCP/IP
  • FOUNDATION fieldbus
  • EtherNet/IP

How do I mount or install remote I/O?

The LB remote I/O is DIN rail mounted. Or, our Systems & Solutions group can provide the system pre-mounted into a custom enclosure. It is certified for Zone 2 mounting.

The FB remote I/O comes installed in an enclosure. Standard options are glass fiber reinforced polyester (GRP), fiberglass, and stainless steel. It is certified for Zone 1 mounting, placing the remote I/O system even closer to field devices.

What can you do with remote I/O?  What kinds of applications or industries is it used in?

Remote I/O is ideal any time you have an application in a hazardous area. Typical applications include oil and gas, pharmaceutical, cosmetics, chemical, food and beverage, etc.


Why is remote I/O better than other options?

The first reason, and this is a big one, is that remote I/O reduces wiring when compared with standard interface technology. Reduced wiring saves time, money, and work. Also, remote I/O works from a decentralized location, meaning that you can put isolated barriers closer to field devices, and that standard field devices can be put into a higher network in terms of hazardous location and advanced technology. Another consideration is that you can get better quality diagnostics with remote I/O than you can with standard intrinsically safe isolators.

Questions about Remote I/O? Get the Engineer's Guide


Topics: Remote I/O

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