Open-Loop Control System:

Control systems are categorized through the control action that is the quantity responsible for activating the control system to generate the output. The two common classifications are open-loop and closed-loop control systems.

An open-loop control system is one in that the control action is independent of the output. An instance of an open-loop control system is a chemical further pump with along a variable speed control. The feed rate of chemicals which manage proper chemistry of a system is determined through an operator, who is not category of the control system. The pump cannot respond through adjusting its feed rate (speed) without operator action if the chemistry of the system changes.

Figure: Open-Loop Control System