Simply put, the core working principle of a differential pressure transmitter is to measure the pressure difference between two different points and convert this physical pressure difference into a standardized electrical signal (such as 4-20mA) or digital signal for output.
Below, we will explain in detail step by step：
1、 Core components
A typical differential pressure transmitter typically consists of three main parts:
Pressure sensing element (core): This is the part that directly senses the pressure on both sides, usually an isolation diaphragm and an oil filled capillary system.
Signal conversion and amplification circuit: converts small changes detected by sensing elements into powerful electrical signals.
Process connectors: such as flanges, threads, etc., used to connect the transmitter to the equipment that needs to be measured (such as pipelines, tanks).
2、 Detailed working process (taking the most common capacitive principle as an example)
Step 1: Pressure Introduction and Isolation
The transmitter has two pressure interfaces, labeled as High Pressure (H) and Low Pressure (L).
These two pressures act on the isolation diaphragms on both sides of the transmitter through process connectors. These membranes are very sturdy and can withstand the corrosion, high temperature, or solidification of process media.
The isolation membrane and the central sensing element are filled with incompressible silicone oil, which plays a role in transmitting pressure and protecting the core element.
Step 2: Convert differential pressure to displacement
High voltage (P ₁) and low voltage (P ₂) respectively act on the isolation membranes on both sides.
The pressure difference Δ P=P ₁ - P ₂ will cause the filled silicone oil to move
The movement of silicone oil will push an elastic element called a "central pressure sensing membrane" (or measuring membrane). This membrane is located between two fixed capacitor plates.
If P ₁=P ₂ (differential pressure is zero), the central diaphragm remains in the middle position.
If P ₁>P ₂, the central diaphragm will undergo a small, proportional deformation (displacement) towards the low-pressure side (L).
If P ₁<P ₂, the central diaphragm will deform towards the high-pressure side (H).
