Open and Closed Loops

Why measure at all?

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Open loop acts blindly; closed loop measures, compares and corrects.
• Error = setpoint − measurement.
• Feedback copes with disturbances that open-loop control can’t see.

Steps

1. Two kinds of control
2. A heater with no thermostat
3. Set it by hand
4. A cold night
5. Spot the feedback
6. Watt’s governor
7. The price of feedback