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Real-world measurements must be communicated and converted into 1s and 0s a controller can understand; the controller’s decisions, in turn, must be communicated and translated into the real-world movements of motors, valves, and actuators. Measurements come in, instructions go out. Beyond that, I/O functionality today is packaged, distributed and delivered in an increasingly bewildering variety of ways.
At one extreme are centralized, cabinet-enclosed I/O modules, mounted together with a power supply on DIN rails and connected via terminal blocks and point-to-point wire pairs to each and every individual sensor and actuator on a given machine. For terminating the wires themselves, machine builders have the option of screw, spring or cage clamp technologies, or may use more expensive but often expedient industrial connectors.
At the other I/O architecture extreme are battery-powered sensors that broadcast their readings wirelessly through a mesh network to a network access point and on to the controller.
“Where’s the I/O now?” one might ask. In between are varying degrees of remote I/O architectures that distribute blocks of I/O in local junction boxes networked back to a central controller, or as industrially hardened blocks mounted directly on the machine frame.
In short, the engineering of machine I/O today is a complex decision-making process that includes far more than simply counting sensors and actuators and making sure you have enough I/O of each type plus a handful of spares in the controller cabinet.
This State of Technology Report explores in greater detail these and other technology trends in the arena of I/O. Drawn from the most recent articles published in the pages of Control Design, this special report includes articles on emerging trends, basic primers and case histories illustrating the latest technology in action.
