🔍 Key Concepts

• Pneumatic proportional controller basic parts: measuring element, controller, final control element • Difference between feedback signal and supply/relay functions in pneumatic systems • Role of the response line in keeping the output in proportion to the input (process variable vs setpoint)

💭 Think About

• Ask yourself: in a proportional controller, what makes the output move in the correct direction AND stop in the right place, instead of just driving fully open or fully closed? • Which part of the system actually compares what the valve (final element) is doing with what the controller is asking for? • Which options describe functions that belong more to the air supply/nozzle system, and which describe a function related to proportional control behavior?

✅ Before You Answer

• Identify which choice clearly describes a feedback path between controller output and the sensing/measuring function • Eliminate any option that talks only about air supply regulation, rather than signal comparison or positioning accuracy • Make sure the option you choose is specifically tied to accurate positioning of the final element in proportion to the process signal, not just checking or adjusting spring forces in the relay