8. Feedback System

We have talked about the 'open loop' system. A more sophisticated control method is called the 'feedback control system' sometimes called a 'closed loop' system. The diagram below shows what this means. You can see that the output is measured and some of it is 'fed back' to become part of the input.

feedback system

The advantage of a feedback system is more precise control.


  • Central heating system with a set temperature control
  • Fridge with a set temperature control
  • Oven with a set temperature control
  • Clothes dryer that can sense how moist the clothes are
  • Anti-lock brakes in a car
  • Picture exposure in a digital camera

The disadvantage is that it is a lot more complicated to make. And so the engineer has to decide whether a simple open loop system is 'good enough' or a more complicated feedback system needs to be designed.

Definition: Feedback is where the output of a system affects the input.


Challenge see if you can find out one extra fact on this topic that we haven't already told you

Click on this link: Feedback Control System