Process gain

What it means

Process gain is the ratio of the change in the process variable to the change in output that caused it, once everything has settled. A high process gain means a small valve movement produces a large process change.

Controller gain and process gain work against each other: the product of the two is roughly what determines loop stability. That is why a loop on an oversized valve — high process gain near the seat — needs a low controller gain, and why the same tuning can be stable at one production rate and unstable at another if the process gain varies with load.

Related

Where this comes up

• Why control valve hunting happens
• Valve position oscillates but the process variable barely moves
• Sluggish control loop
• Flow loop unstable
• Pump speed loop hunting
• Noisy PV and valve chattering
• DeltaV PID parameters explained
• Ovation PID parameters explained
• SIMATIC PCS 7 PID parameters explained
• Rockwell PIDE PID parameters explained
• Yokogawa Centum PID parameters explained
• Honeywell Experion PID parameters explained
• Foxboro I/A PID parameters explained
• ABB 800xA PID parameters explained
• GE Mark VIe PID parameters explained
• Mitsubishi MELSEC PID parameters explained
• Allen-Bradley PID parameters explained
• Schneider Modicon PID parameters explained
• How to tune a Honeywell PID
• PID calculator
• FOPDT calculator
• DCS PID converter
• Proportional band and gain converter
• PID algorithm form converter
• Feedforward gain calculator
• Valve characteristic selector
• Bump test procedure
• PID tuning cheat sheet
• Tuning flow control loops
• Tuning pressure control loops
• Tuning level control loops
• Tuning temperature control loops
• Tuning pH control loops
• Dead time
• Time constant
• Proportional band
• PID offset
• Cascade control
• Gain scheduling
• Lambda tuning
• Bump test
• First-order plus dead time (FOPDT)
• Feedforward control
• Shrink and swell
• Ratio control
• Split-range control