The double flange differential pressure transmitter consists of two key components: the measuring diaphragm assembly and the electronic signal processing unit. The measuring membrane box component includes two flange interfaces, which respectively connect the positive pressure side (high pressure end) and negative pressure side (low pressure end) of the measured medium. Each flange is equipped with a high-precision pressure sensor (usually capacitive or diffused silicon) inside, which is covered with a layer of isolation membrane on its surface. The membrane is connected to the filling liquid (such as silicone oil) inside the transmitter body through a capillary tube. When the measured medium flows into the positive and negative pressure side flanges, the pressure on both sides acts on the isolation diaphragm. For example, when measuring the liquid level of a storage tank, the positive pressure side flange is connected to the bottom of the tank (to withstand the hydrostatic pressure of the liquid+the gas pressure inside the tank), and the negative pressure side flange is connected to the top of the tank (to withstand only the gas pressure). The pressure difference between the two sides reflects the height of the liquid level. The pressure difference is transmitted to the surface of the sensor through the filling liquid, causing changes in the internal capacitance value (capacitive) or resistance value (diffused silicon) of the sensor. Taking a capacitive sensor as an example, the pressure difference causes the distance between the moving plate and the fixed plate to change, and the capacitance value changes linearly, with the change proportional to the pressure difference. The weak electrical signal output by the sensor (such as millivolt level) is converted into a standard signal (such as 4-20mA DC or digital signal HART, RS485) through the amplification circuit, temperature compensation circuit, and linearization processing circuit inside the transmitter. For example, a certain model of transmitter can output a 4-20mA current signal within the differential pressure range of 0-100kPa, where 4mA corresponds to 0kPa and 20mA corresponds to 100kPa, achieving a linear mapping between pressure difference and electrical signal.