If the position of an object oscillates about the switching point, then you need a position sensing switch with snap action and mercury wetted contacts.

Question

Quizplus · Accepted Answer

Mercury wetted contacts are not necessary for applications involving oscillation around a switching point; they are one option among many for reducing contact bounce in switches. Snap action switches can provide the necessary quick switching without specifically requiring mercury wetted contacts.

If the Position of an Object Oscillates About the Switching