A temperature controller is a device that is used to control and monitor the temperature. These temperature controllers receive sensor signals and control heaters or other devices to maintain a preset temperature. They can also be used for humidity, pressure, and flow-rate control. A temperature controller is a device that is used to control and monitor the temperature.
An example of an application will be when the controller takes an input from a temperature sensor, it has an output that is connected to the control element such as a heater or fan. The controller is usually just one part of a temperature control system.