Programmable logic controllers (PLCs) and temperature controllers serve many of the same functions in manufacturing for automating manufacturing processes, minimising staff oversight while ensuring consistent quality.
Process control devices have existed in various forms since at least the 17th century, as temperature regulators in furnaces, and later in to the 18th & 19th centuries as flyball governors on steam engines, boiler valves and other mechanical systems.
PLCs are a more modern tool that came about as a result of increased factory automation in the 20th century, particularly since the 1970s. Prior to this the same function was served by an array of mechanical components which were costly to install & repair and complicated to change when factory operations were modified (for example; if a product line was updated).
However, despite many similarities in their intended functions there are substantial differences in their setup, programming & application that often means a temperature controller is a more efficient and practical solution.