Mercury switches have one or more sets of electrical contacts in a sealed glass envelope that contains a small quantity of mercury. The envelope may also contain hydrogen at pressure, an inert gas, or a vacuum. Gravity constantly pulls the drop of mercury to the lowest point in the envelope. When the switch is tilted in the appropriate direction, the mercury touches a set of contacts, thus completing an electrical circuit. Tilting the switch in the opposite direction moves the mercury away from that set of contacts, breaking that circuit.
- The contacts are enclosed, so oxidation of the contact points is impossible.
- In hazardous locations, interrupting the circuit does not emit a spark that could ignite flammable gases.
- Contacts stay clean, and even if an internal arc occurs, the contact surfaces renew on every operation, so they don’t wear out.
- Even a small drop of mercury has low resistance, so switches can carry useful amounts of current in a small size.
- The sensitivity of the drop to gravity provides a unique sensing function and lends itself to simple, low-force mechanisms for manual or automatic operation.
- The switches are quiet, as no contacts abruptly snap together.
- The mass of the moving mercury drop provides an over-center effect to avoid chattering as the switch tilts.
1 x Mercury Tilt Switch – 10Pcs.