Proportional Mode Basics

Note that many analog controllers used proportional band instead of gain for the proportional mode tuning setting. Proportional band is the % change in the process variable (∆%PV) needed to cause a 100% change in controller output (∆%CO). A 100% proportional band means a 100% ∆%PV would cause a 100 % ∆%CO (a gain of 1). It is critical that users know the units of their controller gain setting and convert accordingly.

Gain = 100 % / Proportional Band

• Proportional Mode Advantages

• Minimize dead time from stiction and backlash
• Minimize rise time
• Minimize peak error
• Minimize integrated error

• Proportional Mode Disadvantages

• Abrupt changes in output upset operators
• Abrupt changes in output upset other loops
• Amplification of noise

1 Like