The core of the intelligent transmitter is a capacitive pressure sensor, which is called "δ"（Figure 1-2）.The sensor isa completely sealed component, the process pressure through the isolation diaphragm and filling liquid silicone oil to the sense of the diaphragm caused by displacement.The capacitance difference between the sensing diaphragm and the two capacitance plate is converted from the electronic components to the electrical signals of the second wire system of the 4 ~ DC 20mA.

      The circuit board module of the intelligent transmitter is a circuit board which adopts a special integrated circuit (ASICS) and a surface packaging technology.The circuit board receives signals from the sensors and is modified and linearized.The output part of the circuit board module converts the digital signal into an analog output signal, and can communicate with the HART controller and the host computer software.　

      The A/D conversion circuit adopts 16 bit low power integrated circuit, and converts the analog current output of the demodulator to the digital quantity, and provides the microprocessor as the input signal.　　 

   Microprocessor control A/D and D/A conversion work, also can complete the self diagnosis and digital communication.At work, a digital pressure value is processed by the microprocessor and used as a digital storage to ensure the precision of the correction and conversion of the engineering unit.In addition, the microprocessor can also complete the sensor's linearity, range ratio, damping time and other functions.    

  Desulphurization, denitration , etc.

Appendix

Reference table for corrosion resistance of transmitter diaphragm

☆  Good         ○  Moderate        ×  Bad