Emerson Exchange 365

Deadband and resolution cause sustained equal amplitude oscillations called limit cycles that cannot be eliminated by controller tuning. A resolution limit causes limit cycles if there is integrating action at just one point in the control loop either in the process (e.g. level), positioner, or the process controller (e.g. PID). Deadband requires integrating action at 2 or more points in the control loop. The best solution is to eliminate the source of the problem but there are fixes.