In two-point control (also discrete or discontinuous control), there are two possible states, namely “on” and “off”.
The control takes place, for example, when the setpoint is reached by the actual value. However, the actual value may fluctuate within the hysteresis range without affecting the control. A two-point control is used when precise adherence to the setpoint value is not required.
The hysteresis represents the range around the setpoint by which the actual value is allowed to fluctuate so that constant switching on and off of the control is prevented. This results in discontinuous or discrete control, where the relevant component, for example the pump of the pump control, receives switching pulses. This in turn results in a fluctuation range with respect to the value reached.
Simple systems, for example in drainage, operate according to this principle. Another well-known example of two-point controllers is the classic heating thermostat, which, for example, regulates the heat in the room with a hysteresis of a few Kelvin.
The 2-point control is realized by a P-controller. The output signal here is proportionally dependent on the input signal, which illustrates the simplicity of the control. There are various possibilities for the technical implementation of the controllers for 2-point control, both mechanical and electronic components are available.