Working principle of intelligent pressure transmitter

Intelligent pressure transmitter is a pressure parameter monitoring device widely used in industrial production control process, and is applied to many fields such as petrochemical, water conservancy and hydropower, railway transportation, etc. It can be used to continuously and accurately measure the process parameters such as pressure, differential pressure, absolute pressure, liquid level, etc. of gas, liquid and steam, and convert the measured signal into 4~20mA DC standard signal and HART signal output through its conversion function, so as to be used by other control and regulation instruments and DCS distributed control systems.

Since intelligent pressure transmitters have the advantages of high precision, small temperature drift, good long-term stability, and rich functions, they are key components for the modernization and automation of industrial production. Therefore, it is particularly important to ensure the reliability of intelligent pressure transmitters, and their reliability has a significant impact on the trouble-free operation of the entire system production process.

The working principle of the intelligent pressure transmitter is shown in Figure 1. Figure 1 mainly includes the δ chamber sensor, sensor excitation and signal conditioning circuit, A/D conversion circuit, microprocessor, D/A conversion circuit, HART communication, display circuit, etc. Among them, the δ chamber sensor is the key component. Since the temperature change of the sensor body needs to be detected, a high-precision temperature sensor is embedded in the positive pressure end of the δ chamber, that is, a pressure-temperature composite sensor is formed. When the external pressure acts on the isolation diaphragm of the δ chamber, the pressure change can be transmitted to the measuring diaphragm located in the center through the transmission of the silicone oil, causing a small displacement (maximum 0.08mm), and the displacement distance is proportional to the pressure. The displacement change of the central measuring diaphragm will cause the capacitance of the two fixed capacitor plates to change, and the pressure change can be detected by the change in capacitance.