In the realm of industrial control and automation, the acronym I/O, representing input/output, is commonly employed. A robust understanding of I/O is crucial for navigating the industry effectively. Presently, two main categories of input/output exist: local I/O and remote I/O. In industrial environments, the latter is the more commonly employed option. To enhance your grasp of the fundamentals of remote I/O and assess its suitability for your particular application, refer to this informative guide.
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.
To comprehend the concept of remote I/O, it is essential to first grasp the general meaning of I/O. In essence, I/O denotes a device that transfers data to or from a computer. These devices play a pivotal role in monitoring and utilizing various critical instruments within the industrial control and automation sector.
Now that you have a basic understanding of I/O, let's delve into one of its primary subsets—remote I/O, also known as distributed I/O. Remote I/O refers to an input/output device situated at a distance from a programmable logic controller (PLC). For instance, the PLC might be positioned in a secure area closer to a control room, while the I/O system is placed nearer to the actual instrumentation under monitoring and control, such as sensors and actuators. Ultimately, remote I/O provides a more flexible utilization of I/O technology.
To enable the operation of a remote I/O system, it depends on a programmable logic controller (PLC). The PLC has the capability to process various data points, encompassing both inputs and outputs. Consequently, these devices can read and transmit data to and from the I/O sections of the PLC device.
These sections may vary, ranging from individual I/O cards, such as digital input cards, to fully integrated segments seamlessly incorporated into the PLC's hardware. Regardless, it is important to note that the PLC is the device responsible for reading and interpreting the data, not the remote I/O system. In addition, the PLC is also responsible for sending commands out while the remote I/O simply acts as a pathway for the data to get to the PLC. Thus, in many I/O setups, the PLC will be located in a completely separate location from the I/O cards or hardware.
Irrespective of its location, the programmable logic controller (PLC) needs to be capable of receiving the data gathered by the I/O hardware. To facilitate the transmission of significant amounts of information between the remote I/O hardware and the PLC, a commonly employed approach involves using an Ethernet protocol or other specialized transmission technologies. Essentially, the remote I/O device utilizes an adapter module connected to the backplane in the PLC rack to communicate with the PLC.
To grasp the fundamentals of remote I/O, it's crucial to explore the advantages that such systems offer. Here are some key benefits of remote I/O:
Reduced Wiring: A primary advantage of a remote I/O system is the significant reduction in required wiring. When the PLC cannot be situated close to the devices and instruments being monitored and controlled, extensive wiring becomes necessary. By opting to place the remote I/O away from the PLC and in proximity to the devices and instruments, the amount of wiring needed is greatly minimized.
Expanded Hardware Configuration Options: The flexibility inherent in a remote I/O setup allows for a broader range of hardware configurations. This increased flexibility provides more options to tailor the setup to best suit the specific requirements of your network.
Facilitating Communication in Harsh Environments: In certain scenarios, placing a PLC directly next to field devices for monitoring and control isn't feasible due to harsh environmental conditions. Extreme temperatures, severe weather, strong vibrations, or other challenging circumstances may necessitate locating the PLC in a secure space—often within or near a control room. Meanwhile, the I/O system can be positioned closer to the instrumentation. Ultimately, remote I/O facilitates communication with the PLC from a safe distance.
Potential Disadvantages of Remote I/O Systems:
While remote I/O systems offer the potential for significant cost savings by reducing wiring requirements, there are certain hidden costs that may arise if precautions are not taken. For instance, users should be aware that implementing remote I/O in a system requires configuring all additional I/O modules. This process can be time-consuming, especially in large systems, where even a modification to one module necessitates the reconfiguration of all other modules. Mindful planning in the implementation of remote I/O modules can help avoid unexpected challenges and costs.
In addition to the potential hidden costs, remote I/O systems have some notable drawbacks, including:
Vulnerability: The communication signals in a remote I/O system depend on a single point of communication between the PLC and the remote I/O hardware. If this point is disrupted or lost, all received data could be lost, and control over the hardware might be compromised. To mitigate this risk, it is crucial to implement redundant communication channels within a remote I/O system.
Hidden Costs of Remote I/O Systems: While remote I/O systems have the potential to generate substantial cost savings by reducing wiring needs, it's crucial to be vigilant about potential hidden costs. For instance, users should be aware that implementing remote I/O in a system requires the configuration of all additional I/O modules. In large systems, even a change to one module can necessitate a significant amount of time spent reconfiguring all other modules. Therefore, careful consideration of how you plan to implement the remote I/O modules in your system is essential to avoid unexpected challenges and costs.