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Selecting a controller for an industrial application can be increasingly difficult with all the options available. These 11 selection criteria can help when deciding among relays, timers, analog instruments, smart relays, programmable logic controllers (PLCs), and programmable automation controllers (PACs). See controller selection table.
Basic choices and selection criteria follow to help in specifying a controller for an industrial application. Eleven criteria in the table can help when selecting a controller type from among relays, timers, analog instruments, smart relays, programmable logic controller (PLCs), and programmable automation controllers (PACs).
Relays, timers, and analog instruments: Despite the proliferation of inexpensive smart relays and micro PLCs, many thousands of control systems are built each year using these basic components. The big advantage of these systems is simplicity, as even the dullest technician can understand and troubleshoot them. No programming is required; thus there is no need for software licenses or PCs. When the number of relays and timers exceeds four, it's best to upgrade to a...