Differential pressure switches are implements to detect changes in relative pressure between two points and are programmed to respond a specific way. Normally the switch will react with an alarm or automatically switch something on or off if differential pressure rises or falls to a set actuation point. This type of pressure switch is mainly used to keep pressures in various parts of a system equalized or to maintain the pressure disparity. These switches can be found in applications such as fuel cells and fridges.
There is one partially differential pressure switch that NASA has helped test and developed that would be suitable to use in the aerospace industry. Optical zero-differential pressure switches are a design of clamped-diaphragm pressure switch. Its purpose is to detect the zero crossing of differential pressure between a tank pressure and a static test pressure. The switch delay for this particular pressure switch was as long as 2 milliseconds.
This switch came about in the hunt for a simple and inexpensive pressure switch that would be able to withstand high differential pressure for millions of cycles without damage. The optical zero-differential pressure switch was evaluated in multiple and uses a fiber-optic displacement sensor is used to detect diaphragm motion. The full-scale tank pressure of the switch is 69 N/sq cm gage and ramping frequency of 1 hertz.