Heater controllers and temperature controllers, also known as process controllers, provide control to a variety of heaters, coils and perfusion heating devices without extensive operator involvement. There are different types of temperature controllers available in the market, such as on-off controllers, proportional controllers, PID controllers and multi-loop PID controllers. The type of input sensor, the type of output and number of outputs, and the method of control should be considered when choosing a controller to integrate into a control system.