In on-off control, what values does the controller signal to the final control element take?

In on-off control, the controller operates in a binary manner where it essentially sends two distinct signals to the final control element: an "on" signal and an "off" signal. The correct choice indicates that the values are 100% positive and 100% negative.

When the controller is in the "on" state, it provides a full signal to activate the control element, which could mean fully opening a valve, turning on a pump, or energizing a heating element. Conversely, when the controller is in the "off" state, it completely shuts off the signal, meaning that the flow of energy or fluid is halted. This clear demarcation of signals (fully "on" or fully "off") is characteristic of on-off control systems designed to maintain a setpoint by toggling between two extremes, thereby creating a simple yet effective method for process control.

The controller does not utilize a range of values or percentages in between those extremes. This is in stark contrast to proportional control systems, where the control signal can vary continuously within a range to provide a more nuanced handling of the process being controlled. In on-off control, only the two binary signals are relevant, highlighting the simplicity and direct nature of this method.