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What is Remote I/O?

In this article, we’re going to explain the terms I/O, Local I/O, and Remote I/O, and why Remote I/O is used in industrial applications.

In the industrial control world, we use the term I/O often. So, let’s begin our discussion today with an explanation of I/O. The focus of our discussion will be on Remote I/O, but we’re also going to talk about Local I/O too.

In this article, we’re going to:

– Explain the terms I/O, Local I/O, and Remote I/O

– Explain why Remote I/O is used in industrial applications

– List 2 transmission mediums used to connect between the local PLC and the Remote I/O

– List 2 transmission protocols used to communicate between the local PLC and the Remote I/O

What I/O Refers to in the Industrial World?

I/O stands for Input/Output.

In the industrial world, I/O refers to any device that transfers data to or from a computer such as a PLC.

For our discussion, we’ll refer to these I/O devices as I/O Modules.

Field Devices such as sensors and actuators are connected to the I/O modules.

The sensor signal representing a process variable such as liquid flow is converted by an Input I/O module and stored in the PLC memory.

The actuator receives an operating signal from an Output I/O module.

Local I/O VS Remote I/O

Local I/O refers to I/O modules that are housed in the same cabinet and likely connected to the controller backplane in the PLC rack.

Remote I/O simply means that the I/O module is at a remote place physically located a distance from the control PLC.

A remote I/O module will speak to the PLC via an Adaptor Module connected to the controller backplane in the PLC rack.

Why Do We Use Remote I/O?

There are several reasons…. let’s look at a few.

1) When it’s not possible to have a PLC near the field devices

In some industrial applications, it’s not possible to have a PLC with Local I/O Modules near the field devices because of the harsh environment.

2) You want to eliminate long lengths of multi-conductor cable

Remote I/O is a solution when you want to place I/O modules close to the field devices in order to eliminate long lengths of multi-conductor cable.

With Remote I/O, signals can be received from far away sensors and control signals can be sent long distances to control valves, motors, and other final actuators.

Remote I/O Transmission Protocols 

Signals can be sent any distance on a high-speed medium such as twisted-pair wires and fiber optics using a variety of transmission protocols such as Ethernet and Profibus.

Summary

Let’s review what we’ve discussed.

– I/O stands for Input/Output

– I/O refers to any device that transfers data to or from a computer such as a PLC

– Field Devices such as sensors and actuators are connected to the I/O modules

– Local I/O refers to I/O modules connected to the controller backplane in the PLC rack

– A remote I/O module is physically located at a distance from the control PLC

Remote I/O’s are used:

– Because in some industrial applications, it’s not possible to have a PLC with Local I/O Modules near the field devices because of the harsh environment.

– When you want to place I/O modules close to the field devices to eliminate long lengths of multi-conductor cable

– Signals can be received from far away sensors and final actuators

– Signals can be sent any distance with a high-speed medium such as twisted-pair wires and fiber optics using a variety of transmission protocols such as Ethernet and Profibus

Want to Learn More?

Be sure to download the RealPars app (iOS, Apple TV, Android, Android TV, firetv, Roku). 

When you download the app, you’ll be able to watch an entire free course on PLC Hardware. Just like this article, the lessons are all high-quality and also very easy-to-follow.

By downloading the RealPars app, you can have access to a wealth of practical knowledge as an automation engineer right in your pocket and you will also receive new fresh out of the oven videos each and every week.

RealPars App Offline Viewing

And the best part is, you don’t even need to have an internet connection to watch the courses on your phone, you can synchronize the videos for offline viewing and watch them even when you don’t have any internet.

Of course, if you’re serious about wanting to learn even more, you can gain instant access to a large number of exclusive RealPars courses covering a variety of industrial automation topics, including PLC and HMI programming, DCS, IIoT, and others, all for a small yearly membership fee.

It’s an amazing value for some really robust content and lots of support. And you’ll be getting the same course work that would cost you a few thousand for one week of offline training!

All of us on the RealPars team look forward to helping you continue to advance your PLC expertise and your career! 

Got a friend, client, or colleague who could use some of this information? Please share this article.

The RealPars Team
By Ted Mortenson

By Ted Mortenson

Automation Engineer

Posted on Apr 13, 2020

By Ted Mortenson

Automation Engineer

Posted on Apr 13, 2020

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