Define 'deadband' in control systems and provide an example.

Define 'deadband' in control systems and provide an example.

• A. A deadband is the maximum allowed deviation before action is taken.
• B. A deadband is the always-on control action to correct errors.
• C. A deadband is a range around SP where no control action occurs; for example, a valve may not move until PV deviates by plus/minus 2%.
• D. A deadband is the rate at which a valve opens with time.

Answer: (C)

Deadband is a region around the setpoint where the controller does not change its output. This keeps small errors or measurement noise from causing constant actuator movement. For example, if the setpoint is 100 and there is a deadband of plus/minus 2 percent, the process variable can vary between 98 and 102 without the valve moving. Only when the PV leaves that band does the controller make an adjustment to push PV back toward the setpoint. The total width of this neutral zone is 4 percentage points. This helps prevent unnecessary wear and hunting by ignoring minor fluctuations, unlike a rule that would trigger action for any tiny deviation.

Deadband is a region around the setpoint where the controller does not change its output. This keeps small errors or measurement noise from causing constant actuator movement.

For example, if the setpoint is 100 and there is a deadband of plus/minus 2 percent, the process variable can vary between 98 and 102 without the valve moving. Only when the PV leaves that band does the controller make an adjustment to push PV back toward the setpoint. The total width of this neutral zone is 4 percentage points.

This helps prevent unnecessary wear and hunting by ignoring minor fluctuations, unlike a rule that would trigger action for any tiny deviation.