The 651C Self-tuning/Digital PID Valve Controller drives MKS 653 or 253 Exhaust Throttle Valves with speed and precision. Its self-tuning algorithm brings the system to set point faster than conventional controllers, and ensures repeatable process recipes without operator involvement. The self-tuning function determines optimal control parameters for any set point in the range of the valve by learning time constants, transfer functions of the valve and plumbing, valve gain, and other important parameters.