Definition
A Programmable Logic Controller (PLC) is an industrial computer that continuously reads sensor and input signals, executes programmed logic against them, and controls outputs (actuators, motors, valves) accordingly: the general-purpose control brain behind most automated machinery. A Safety PLC is a specialized variant certified specifically for safety-related control functions.
Key facts
- A general-purpose programmable controller executing custom logic, distinct from a fixed-function relay or simple switching device.
- Continuously cycles through reading inputs, executing logic, and updating outputs at high speed.
- The foundational control device behind most industrial automation, from a single machine to a coordinated production line.
- Distinct from a Safety PLC, which is specifically certified and architecturally designed for safety-related functions with independent, redundant verification.
How does Programmable Logic Controller work in maintenance?
A PLC continuously reads the state of connected sensors and inputs, executes a stored logic program that determines what outputs should do based on those inputs, and updates connected actuators, motors, or indicators accordingly, cycling through this process many times per second to provide real-time machine or process control.
What does Programmable Logic Controller require?
A standard PLC handles general machine and process control logic. A Safety PLC is a specifically certified, architecturally distinct variant designed and validated for safety-related functions (such as emergency stop circuits or guard monitoring) with independent verification and redundancy that a standard PLC is not certified to provide.
FAQ
Frequently asked questions
Which control task does a PLC take on?
A PLC takes on general machine and process control: reading sensor inputs, executing programmed logic, and controlling connected actuators accordingly, distinct from the safety-certified role of a Safety PLC.
Last reviewed: