Derivative Mode Basics

Nearly all derivative tuning settings are given as a rate time in seconds or minutes. The effective rate time setting must never be greater than the effective reset time setting. The effective settings are for an ISA Standard Form. The advantages and disadvantages of the derivative mode are similar to that of the proportional mode except the relative advantages is less and the relative disadvantages are greater for the derivative mode.

Seconds = 60 ∗ minutes

• Derivative Mode Advantages

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

• Derivative Mode Disadvantages

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