A differential pressure (DP) transmitter measures the pressure difference between two connection ports (P₁ high and P₂ low). The internal sensing diaphragm deflects based on this pressure change. This mechanical movement is converted into a linear electrical output signal—typically a standard 4–20 mA current—for industrial control systems.

• The high-pressure side (P₁) connects to the higher pressure source, and the low-pressure side (P₂) connects to the reference or lower pressure source
• Process pressure pushes against the external isolation diaphragms. Fill fluid (like silicone oil) transfers this pressure to the central sensing diaphragm.
• If P₁ is greater than P₂, the net force causes the central sensing diaphragm to flex toward the low-pressure side.
• The deflection changes electrical properties (such as capacitance between plates or strain gauge resistance).
• The internal electronics process this change, linearize it, and transmit a standard 4–20 mA signal proportional to Δ P = P₁ – P₂