Temperature controllers accept inputs from temperature sensors or thermometers, and output a control signal to keep the temperature at the desired level. Temperature controllers use several different control techniques. Limit control establishes set points that, when reached, sends a signal to stop or start a process variable. Linear control matches a variable input signal with a correspondingly variable control signal. Feedforward control does not require a sensor and provides direct control-compensation from the reference signal. Proportional, integral and derivative (PID) control requires real-time system feedback. PID control monitors the error between the desired variable value and the actual value, and adjusts the control accordingly. Fuzzy logic is a control technique in which variables can have imprecise values (as in partial truth) rather than a binary status (completely true or completely false). Temperature controllers that use advanced or non-linear controls such as neural networking, adaptive gain, or emerging algorithms are also available.

