Easy xLogic, User Manual, Page: 151 / 226

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The control device is formed from the actuator and the control.
The control and controller together form the regulating device.
The following picture gives an abstract portrayal of the situation described above.
The comparing element uses the sensor to compare the command variable with the process
value. If the command variables and process value deviate from one another, this results in a
positive or negative loop error that in turn changes the process value.
Control loop
The process value x influences the manipulated variable M by means of the regulating device.
This creates a closed circuit that is also known as a control loop.
If, in the example above, the window is opened, the temperature in the room drops. The person
must increase the heat output of the heater. If the heat output is increased too much, it will get
too hot. The person must then reduce the heat output.