Mercury switches are switched on and off according to the movement of mercury encapsulated in the tiny glass tube.
In comparison to mechanical switches, mercury switches have the following characteristics:
- Mercury switches can be used in harsh or extreme environmental conditions. Since the mercury switch is sealed and the mercury inside is isolated from the outside world in it's glass tube, it can be successfully employed in environments with oil, steam, dust and corrosive gases.
- Mercury is the only metal that remains liquid at room temperature. The characteristics of liquid Mercury (high density and surface tension) lend themselves to the operation of this tiny switch and allow it to operate uniquely upon contact with external forces such as vibration and movement.
- Conductivity: Mercury switch contact resistance between the electrodes is typically less than 100 m Ω.
- Current: These switches employ tungsten wires. The maximum allowable current of a tungsten wire electrode is 10A, while the maximum allowable current of a common alloy wire is generally only 1A.
- The flow of mercury switches is solely determined by gravity, so it can work reliably for a very long time. Remember how rugged the old Mercury wall thermostats used to be before they were replaced by digital ones?