guard ring

noun
1.
a ring worn tightly in front of another ring to prevent the latter from slipping off the finger.
Origin
1810-20
Examples from the web for guard ring
  • The guard ring is also included at the same voltage as the sensing plate in order to reduce fringe effects.
  • For minimal edge-effect field disturbance, a guard ring is generally placed around the upper plate.
British Dictionary definitions for guard ring

guard ring

noun
1.
(jewellery) Also called guard, keeper ring. an extra ring worn to prevent another from slipping off the finger
2.
an electrode used to counteract distortion of the electric fields at the edges of other electrodes in a capacitor or electron lens