Editing Setpoint (control system) (section)

==Examples==

'''Cruise control'''

The <math>SP-PV</math> error can be used to return a system to its norm. An everyday example is the [[cruise control]] on a road vehicle; where external influences such as gradients cause speed changes (PV), and the driver also alters the desired set speed (SP). The automatic control algorithm restores the actual speed to the desired speed in the optimum way, without delay or overshoot, by altering the power output of the vehicle's engine.  In this way the <math>SP-PV</math> error is used to control the PV so that it equals the SP. A widespread of <math>SP-PV</math> error is classically used in the [[PID controller]].

'''Industrial applications'''

Special consideration must be given for engineering applications. In industrial systems, physical or process restraints may limit the determined set point. For example, a reactor which operates more efficiently at higher temperatures may be rated to withstand 500°C. However, for safety reasons, the set point for the reactor temperature control loop would be well below this limit, even if this means the reactor is running less efficiently.