ESR (Equivalent Series Resistance)

Category: science

The internal electrical resistance of a capacitor during high-frequency alternating current operation.

As electrolytic or tantalum capacitors age or suffer heat stress, their internal fluid dries out, causing their ESR to spike. A high ESR prevents the capacitor from smoothing out raw voltage ripples, introducing electrical noise that causes system instability, random reboots, or data corruption.

Common Examples

• The server motherboard suffered from random crashes under heavy load because the filtering capacitors developed a high ESR profile.
• An in-circuit ESR meter allows bench technicians to verify capacitor health metrics without desoldering the unit from the board.