Pressure switches are typically contact switches, meaning they fit into a container of liquid to measure pressure. Because most units are very small, the displacement of the unit is factored into the measurement. The unit is composed of two sections—the transducer unit and the switch unit. The transducer is the piece of equipment that measures the pressure in the container, and can be set to identify ascending pressure, descending pressure, or, in some models, multiple pressure points. When the set pressure is met, the transducer sends a signal to the switch unit, which converts that message into electrical energy. This energy triggers the next step in the application. In a fuel gauge, for instance, this electrical energy can be used to activate a warning light if the pressure gets too low. In rocketry, scientists can monitor pressure to prevent explosions. In petroleum mining, workers can learn if they are in danger of hitting an air pocket and creating an explosion.
