Automation—It’s All About the I/O

Inputs and outputs (I/O) are fundamental to the world of computing, industrial control and data/information processing. Without them, industrial and electronic devices of all kinds would have no way of receiving data, and the user would have no way of manipulating or interacting with the data sources. Since they form the basis of our relationship with almost all the industrial devices we use, it’s important to understand how I/O modules function.

As a key component of industrial systems, I/O modules ensure connectivity and control of systems, processes and devices. They usually include analog channels, digital channels or a combination of both. Analog inputs can detect various signals including frequency, voltage or current. Digital I/O are used for low-level on/off signals. I/O modules that have analog inputs and digital outputs often incorporate an analog-to-digital (A to D) converter to process the signal.

Essentially, I/O modules act as mediators between a central processor and the industrial device. For example, the input modules on a programmable logic controller (PLC) receive signals from switches, sensors, transmitters, actuators and other equipment connected to it. The output modules on the PLC send response signals to the devices controlled by the PLC in response to the received signals.

Common functions enabled by I/O include:

• Device communication:An I/O module can perform multiple device communication functions, such as status reporting, sending/receiving commands and information transfer.
• Control and timing:To properly manage the flow of information between a computer or industrial system and an external device, an I/O module uses a processor’s internal resources to perform time management.
• Processor communication:Completing processor communication requires an I/O module to carry out such tasks as decoding and accepting commands and recognizing its own address on the network.
• Error detection:An I/O module can detect an array of problems between the systems to which it is connected, including mechanical errors and data-related issues during transmission.
• Data buffering:One of the most important capabilities of an I/O module is that it can manage the transfer speed between the devices to which it is connected.

Centralized or distributed

A highly centralized I/O system is characterized by concentrated I/O hardware in a single entity, with network or hardwired connections extending from that location. A highly distributed I/O system, on the other hand, has the I/O hardware distributed across many operational and physical areas, with localized network or hard-wired connections extending from these remote locations.