Differential Pressure Switches
Differential pressure switches are a type of pressure transducer that senses changes in the relative pressure between two points and responds in a specified way. Differential pressure is one of the several types of measurement that are available for pressure switches.
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Applications of Differential Pressure Switches
In a given application, a differential pressure switch may be used to maintain a disparity of pressure in separate parts of a system or keep the pressure in various parts of a system equalized. Differential pressure switches are important for the utility, automotive, aerospace, appliance, pneumatics, and hydraulics industries because they are able to help manage the comparative pressures of different points within a system.
In airplanes, they are used to monitor and regulate the differential between the cabin air pressure and the atmospheric pressure as it changes throughout the duration of the flight. Oil filters for internal combustion engines are regularly equipped with differential pressure switches to measure the change of pressure across the filter. Differential switches can also be used to measure flow or level between connected pressurized systems or pressure vessels, since pressure tends to equalize within a free-flowing system.
Differential Pressure Switch Design
Differential pressure switches come in many forms, with or without either analog or digital displays, and in a variety of housing materials, including acetal, brass, polycarbonate, plated steel, glass reinforced polyester, polyvinyl chloride, and cast aluminum.
Electronic pressure switches are the most common type of differential switches because they are easy to program and suitable to a wide range of pressures. Electronic differential pressure switches function by measuring strain on two separate piezoresistive, piezoelectric, or magnetic sensors that are connected to a digital interface module, which shows the relative pressure.
How Differential Pressure Switches Work
Differential pressure switches simultaneously measure the pressures at two different places in a system and compare them to produce a differential pressure reading. If the pressure is the same at both points, then the differential pressure will read zero. If there is a difference in pressure between the two points, then the differential pressure reading will quantify the difference in terms of pressure – usually atmospheres (atm), Pascals (Pa), pounds per square inch (PSI) or bar.
Differential pressure switches are programmed to react when the differential pressure rises or falls to a set actuation point, either signaling an alarm or automatically switching something on or off (for instance, opening or closing dampers or louver and starting and stopping fans or motors). Different kinds of differential pressure switches are designed to sense and react to changes in relative pressures of gases, liquids, or both.