Communicating level switches

Communicating level switches can be used to measure the level of a communicating body of liquid. Located in a column of liquid external to the process container, they are suitable for measuring the local level in high pressure and temperature situations.
Similar magnetic communicating level indicators have advantages that make them more suitable in applications involving fluids at high-pressure or high temperature or which are flammable, explosive, chemically aggressive, polluting, harmful or poisonous for man.  
The principle of communicating vessels dictates that a liquid contained in two or more containers connected to each other, in the presence of gravity, will reach the same liquid level and will share the same surface equipotential.