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With the development of microelectronics, computer technology, and communication technology, traditional analog pressure transmitters have been combined with fieldbus technology, giving rise to fieldbus pressure transmitters. The HART protocol is a universal fieldbus protocol that is compatible with the traditional 4-20mA analog communication standard. It enables the simultaneous transmission of analog and digital signals through loop carriers, and the additional communication protocols allow for the digital and intelligent management of instruments. The reasons that may cause errors in pressure transmitters during pressure transmission are as follows: 1. Leakage; 2. Wear and tear (especially when cleaning agents are used); 3. Presence of gas in the liquid pipeline (causing head error); 4. Presence of liquid in the gas pipeline (causing head error); 5. Differences in density due to temperature differences between the two pressure conduits (causing head error). The methods to reduce errors in pressure transmitters are as follows: 1. Keep the pressure guide tube as short as possible; 2. When measuring liquids or steam, the pressure guide tube should be connected to the process pipeline upward, with a slope of not less than 1/12; 3. For gas measurement, the pressure guide tube should be connected to the process pipeline downward, with a slope of not less than 1/12; 4. In the case of liquid pressure guide tubes, avoid having high points in their middle, while for gas pressure guide tubes, avoid having low points in their middle; 5. Maintain the same temperature between the two pressure guide tubes; 6. To prevent frictional effects, the diameter of the pressure guide tubes should be large enough; 7. There should be no gas present in pressure guide tubes that are filled with liquid; 8. When using an isolation fluid, the liquid in both pressure guide tubes should be the same; 9. When using a cleaning agent, the connection point of the cleaning agent should be close to the pressure tapping point on the process pipeline. The length and diameter of the pipelines through which the cleaning agent flows should be the same, and it should be avoided that the cleaning agent passes through the transmitter. The communication condition for HART protocol smart pressure transmitters is that the loop resistance must be ≥250Ω, and the operating voltage must fall within the specified range for communication; for example, the communication requirements for the 3151 pressure transmitter are a loop resistance of 250Ω, a very low communication voltage of 18 V DC, and correct connection of the power supply. If communication still occurs in this way, there are the following reasons. (1) The communication cable is not properly connected. Check that the cable plug is securely inserted and that the terminal screws are not loose, to ensure good contact. (2) The cable is in the wrong position. The handheld terminal can be connected to terminals A and B, or to both ends C and D of the load resistor R; however, it cannot be connected to points A and D. A resistor of ≥250Ω is required between the power supply and the handheld terminal; its function is to prevent the low-impedance power supply from diverting the communication signals. However, the value of R should not be too high, as this is necessary to maintain the very low operating voltage of the transmitter, thereby ensuring that the handheld terminal can read information from the transmitter and send the configured parameters to its memory. Since the internal resistance of the power supply is very low, it can be considered a short circuit; connecting it to the AD terminal is equivalent to connecting both ends of the communication cable at the same point. As a result, communication is not possible, and it is thus impossible to read information or set configuration parameters. Leveraging its core technologies in sensors and smart circuit boards, Huaheng Instruments is able to modify these core technologies at low cost to meet customer requirements, thereby enabling the customization of personalized products. The main products include the SMART series of pressure transmitters, multi-parameter transmitters, flow meters, temperature sensors, and level (liquid level) instruments. These offer industrial automation devices with a high performance-to-price ratio for industries in China such as power, petroleum, chemicals, metallurgy, cement, and mining. The information was compiled by Huaheng Transmitter Manufacturer.