Thermostats are used for temperature control. But there are more ways to regulate the temperature, depending on the type of thermostat. The most common is regulation by hysteresis. Smarter is PI control, which can regulate temperatures with smaller fluctuations and can "predict" how the heat source needs to be switched.

15.1.2024

Hysteresis control is the simplest and most commonly used method for thermostats. In this control, two temperature values are set - an upper and a lower limit. When the temperature reaches the upper limit, the thermostat turns off, when the temperature drops below the lower limit, the thermostat turns on. This causes the thermostat to cycle on and off. The hysteresis value determines the difference between the upper and lower limits that is required for stable control. Hysteresis control typically uses relays to control the thermostat on and off.

On the other hand, PI temperature control is a more sophisticated method used in more advanced thermostats. PI control combines two basic components - proportionality and integration. The proportional part takes care of the immediate response to temperature changes and assigns more or less heating or cooling power to the thermostat. The integral part monitors the duration of deviations from the desired temperature and serves to eliminate constant deviations. This provides even more precise temperature control.

PI control is often used in electronic thermostats with microprocessors that can perform calculations and adaptively adjust control parameters. This provides better accuracy and stability of temperature control compared to hysteresis control.