Rievtech xLogic ELC Series User Manual page 173

Characteristics when configuring
Observe the Control and regulate basics.
Control and regulate
In engineering, quantities can be both controlled and regulated.
When controlling, a quantity is manipulated without being able to compensate for outside influences.
When regulating, a quantity is maintained at a specific value in order to compensate for outside
influences.
In the following example, controlling means that the person can set the heat output at a fixed value. The
heater cannot compensate for the drop in room temperature when a window is opened.
In the example below, regulating means that the person can increase the heat output if the room
temperature drops to below 20 °C. If the room temperature rises above 20 °C, the heat output is
reduced.
Basic concepts of regulating
In the example, the current for the electric heating is the manipulated variable. The changeable
resistance is the actuator. The hand that operates the actuator is the control. The actual room
temperature is the controlled variable or the process value. The desired room temperature is the
command variable or the setpoint value. The electric heating is the control process. The thermometer is
the sensor. The temperature loss from opening the window is the disturbance variable.
So this means that the person measures the process value (room temperature) with the sensor
(thermometer), compares the process value (room temperature) with the command variable (desired
room temperature) and uses the actuator (changeable resistance) to manually regulate the manipulated
variable (heating current), in order to compensate for the disturbance variable (temperature drop from
opening the window). The person is therefore the controller.
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