Plain English Meaning

A helper mechanism inside the instrument does some of the work, so the needle reacts faster and more accurately than it would on its own.

Full Definition

Describes an instrument or control system in which a small input drives a secondary mechanism (a servo) that provides the actual sensing or actuating force, producing a faster or more accurate response than a purely mechanical system. In a servo-assisted vertical speed indicator, a servo mechanism augments the standard pressure-diaphragm sensing to display rate-of-climb or descent changes more quickly and with less lag.

Context Anchor

Seen in discussions of the vertical speed indicator, especially when comparing pressure-operated instruments with designs that respond more quickly.