A diaphragm pressure gauge, also known as a membrane pressure gauge, is a device that utilizes the deflection of a flexible thin membrane called the 'diaphragm' to measure the pressure of the fluid in a system.This pressure gauge measures air pressure inside an aircraft cabin. The diaphragm pressure gauge is used to monitor the cabin pressure during flight as well as other parameters such as barometric pressure, temperature, humidity, etc. This device is made up of two parts, the diaphragm, and the casing. The diaphragms are connected to each other via a rubber tube. When there is a change in pressure, the diaphragms will flex and the rubber tube will expand or contract accordingly.