For further analysisIntelligent pressure transmitterTo address the issues of instrument power supply and impedance matching in applications, it is necessary to first understand the basic working principle of intelligent pressure transmitters. The intelligent pressure transmitter is composed of two H-shaped vibration beams on a monocrystalline silicon resonant sensor, which respectively convert differential pressure and pressure signals into frequency signals, send them to a pulse counter, and then directly transmit the frequency difference to the CPU for signal processing; Convert to a 4-20mADC output signal corresponding to the input signal through a D/A converter, and superimpose a BRAIN/HART digital signal on the analog signal for communication. The built-in characteristic correction memory in the membrane box component stores the environmental temperature and static pressure of the sensor, and the input/output characteristic correction data is input into the CPU operated liquid level transmitter. Data is transmitted through digital communication with external devices (such as handheld smart terminals BT200 or BT275 and I/O cards with communication functions in DCS) through I/O ports. The digital signal is superimposed on the 4-20mA signal line and does not cause any disturbance to the 4-20mA signal.

Intelligent pressure transmitterIn practical applications on site, the most commonly encountered problems are instrument power supply and impedance matching. Except for EJA and ST3000 smart transmitters, other smart transmitters also have the same problem. The maximum load resistance and supply voltage of Rosemount's 3051 smart transmitter also need to meet the corresponding relationship shown in Figure 5, that is, R=43.5 × (U-10.5), and the ripple of the DC power supply should be less than 2%. For CSA certified transmitters, the supply voltage cannot exceed 42.4V. It can be seen that smart transmitters have strict requirements for the amplitude and load resistance of the minimum operating voltage, and special attention should be paid in applications.

During use and maintenance, it is important to carefully read the information provided by the smart transmitter and DCS system; The technical requirements for the normal operation of on-site instruments and DCS systems need to be thoroughly discussed; Combined with practical work, the wisdom of instrument engineering technicians is utilized to handle the power supply and impedance matching issues of intelligent transmitters, thereby improving the maintenance level of instruments, promoting the use of intelligent transmitters, and creating conditions for improving the automation level of petrochemical production.