In valve control loops, what does chatter refer to?

• A. Slow drift of setpoint
• B. Random electrical noise
• C. Thermal expansion causing misalignment
• D. High-frequency oscillation or rapid opening/closing of the valve

Answer: (D)

Chatter is the rapid, high-frequency motion of the valve—opening and closing back and forth around the commanded position. It happens when the feedback loop responds too aggressively or when the valve and process dynamics interact in a way that prevents a stable settle, causing the controller to continuously correct a small error. This can arise from excessive loop gain, aggressive tuning, or valve dynamics like deadband and friction, and it leads to wear, wasted energy, and degraded control accuracy. It’s not a slow drift of setpoint, not random electrical noise, and not a gradual thermal misalignment; those conditions produce different symptoms, whereas chatter is specifically the quick, oscillatory valve motion.