Who Really Controls the Process? Inside the Control Valve | Day 3 A–Z Instrumentation Challenge No sensor changes the process. No PLC moves the fluid. 👉 The control valve does. Welcome to Day 3 of the A–Z Instrumentation Challenge by Diopter Technologies Limited, where we break open the most powerful final control element in any process plant — the Control Valve. A control valve doesn’t just open and close. It listens to the controller, interprets signals, and physically reshapes flow, pressure