A regulator is a device that is used to influence the regulated system to achieve and maintain a desired state.
A wide range of physical variables can be used as control variables (temperature, relative humidity, CO2 concentration, …). The regulators are mostly connected in negative feedback. The input variable is not directly the absolute value of the monitored variable, but only the deviation from the desired value. The regulator then influences the whole system so that the deviation is eliminated or is within the prescribed limits.
Regulators are most often used in automated systems where they evaluate and adjust the regulated system in real time to the satisfaction of the user. The regulation of the system can operate continuously or discretely over time. It all depends on the controlled variable and the purpose of the control. Regulators help to make the operation of all equipment more efficient and thus reduce their operating costs.