Microprocessor-based on-site smart meters are generated in line with fieldbus. Similarly, the application of on-site smart meters also provides a good foundation for the development and application of fieldbus and raises new questions for expert research. At the present stage, the on-site intelligent instrument is just as described in the related literature, due to the incompatibility of the communication protocol and the consideration of the conventional instrument 4-20mA.
Analog signal transfer hold. Is a last resort transition product. Really smart field instruments that can't really fit into a fieldbus. It can neither reduce the initial installation cost of the control system. It is also unable to give full play to its own superior functions, and it cannot realize the exchange and operation of mutual information between on-site smart instruments.
however. After all, the smart transmitter represents the rise of new generations of transmitters. It uses a lot of high-tech today. Such as sensing technology, microelectronics digital processing technology, compared with the regular transmitter, with high precision, good stability, high reliability, wide measurement range, large range ratio and so on. What is more advantageous is that it implements digital communication functions. Through the DCS system or field communication controller with the same communication protocol, various parameters of the smart transmitter can be changed and set to achieve remote debugging and human-machine dialogue. Online monitoring of various data. Like all smart meters, smart transmitters also have complete self-diagnostics. It can be said that the current smart transmitter is a new transmitter that replaces the past and represents the development of future field instruments.
2 Applications of Smart Differential Pressure Transmitters The following are examples of practical applications of smart transmitters and their various characteristics to solve various problems that arise in process control scenes. It should be pointed out that various types exist in the market. Smart transmitter. The intrinsic features will not be the same, so the individual examples cited in this article may not necessarily be generic. Please ask the reader for Kam.
2.1 Actual verification of differential pressure in the original design. A differential pressure flowmeter is used for air flow measurement. Air is used to adjust copper ratio after regeneration of copper scrap. This set of flowmeters has a design differential pressure of 10KPa. But it has not been able to operate normally. Field operators can only rely on experience to judge and control air flow, accompanied by arbitrariness and blindness to process operations; Excessive air volume can increase the oxygen content in the system and threaten the safety of the system. Considering that the air flow is small, the process piping is small, and the corresponding art parameters in the original design are biased, which makes it theoretically insignificant to verify the original design differential pressure value.
After applying the smart differential pressure transmitter. Use the smart differential pressure transmitter to display the input differential pressure value. The unit can be selected from the specified series, and it is very convenient to actually verify the design differential pressure value. With the cooperation of the post personnel, the actual differential pressure value and the maximum differential pressure value of the flow meter are actually measured. Surprisingly, the maximum differential pressure reached 100KPa. 10 times the original design value, no wonder that the original differential pressure flowmeter can not operate normally. According to the differential pressure value, the smart terminal is used to modify the measurement upper limit of the transmitter and the air flow is automatically measured. Solve the problems that have not been solved in history and have long been troubled.
In differential pressure flowmeter applications. Especially in the measurement of small flow and small pipelines, there may be a series of problems such as detailed description of the process parameters or serious deviation from the actual conditions. The serious error caused by the original setting differential pressure value, resulting in the entire set of flow meter anomalies. At this point, the reference to the smart differential pressure transmitter can play a role in simplifying the use of it directly with the actual measurement of the differential pressure before and after the throttle, according to which the original design value is modified to make difficult problems solved.

2.2 Simplify the system components The smart differential pressure transmitter only needs to obtain the output signal with the square root relation of the input differential pressure signal through a simple setting, thus avoiding the use of a differential pressure flowmeter. Simplifies the composition of measurement and control systems. The benefits are self-evident. Simultaneously. After the prescribing small signal cut again has its own uniqueness. There are two ways to cut off the small signal. One of them is like a normal squarer, and it is completely cut off when the output signal is smaller than the cutoff point. As shown in Figure l. Call it "zero cut method": The second is when the output signal is smaller than the cut off point. The output signal is linear with the input differential pressure signal. As shown in Figure 2, it is called "linear cut mode." The resection point for both resections was continuously adjustable between 0% and 20%. Comparison of Figure 1 and Figure 2 shows. The linear cutting method is useful for on-site operation when measuring the lower limit flow.
2.3 Reducing the number of meter spare parts For medium nitrogen enterprises, the measurement of the flow of hydrogen and fluorine mixed gas in the inlet of the ammonia converter tower has a large flow rate measurement and a small flow rate measurement. Large flow rate for the normal production of the synthesis tower. The small flow rate is used in the temperature-recovery stage after the synthesis tower catalyst is updated. When using a conventional differential pressure transmitter. In the temperature-reduction stage, a small-range differential pressure transmitter (the actual differential pressure value of the plant is 16KPa, and the measurement of the safety gas volume (ie, small flow rate) when the electric furnace heats up) is required; after the temperature-reduction stage is over, the synthesis tower is put into operation. During normal production, it is necessary to re-install a large range of differential pressure transmitter (actual differential pressure value is 254KPa). Usually a conventional differential pressure transmitter does not have such a large turndown ratio. For full production needs, the flow rate The measurement is actually equipped with two differential pressure transmitters.
The use of smart differential pressure transmitter has a large range ratio. And self-setting, self-checking ability. Use it for mainline flow measurement. Only the intelligent terminal needs to perform the modification of the small range differential pressure and the large range differential pressure value in the control room to accomplish the same purpose. Avoids the disassembly verification of conventional differential pressure transmitters. Reduce the amount of meter maintenance and reduce the number of spare parts. The conventional differential pressure transmitter has a smaller range than Yu. Like the familiar 1151 differential pressure transmitter. The range ratio is 6:1, while the smart transmitter's range ratio can reach at least 30;1. Generally up to 50:1. Obviously. If the smart transmitter is used as a backup for the conventional 4-20mA output transmitter, the specification and quantity of the spare meter can be greatly reduced.
2.4 Facilitate the On-Site Display of Various Parameters The simple setting of the instrument enables the intelligent transmitter to have an LCD module to display a variety of different data. Such as pressure transmitter. Allows the LCD to directly display the input pressure and the corresponding unit, differential pressure transmitter, which allows the LCD to indicate the unit's own flow engineering value. In some occasions, it is possible to omit on-site indicating instruments, such as pressure gauges, rotameters, etc. without affecting the on-site monitoring and operation. The LCD display module has a mandatory self-diagnosis display function. Once the measured parameter exceeds the range or the transmitter itself fails, the LCD will display the error code instead of the display of the original set parameters, which will facilitate timely troubleshooting. If you pass the smart terminal, you can read out more process information from the transmitter.
3. Problems that need to be improved technically are also found in use. Smart transmitters still have technical problems that need to be improved.
(1) How to realize the encryption of the transmitter and ensure the authoritativeness of various setting data.
(2) How to reduce the power supply requirements of the transmitter when communicating. Easy on-site commissioning and maintenance.
(3) How to separate other information measured by the transmitter, such as ambient temperature, process medium static pressure, differential pressure, etc., that can be displayed on the smart terminal. To reach a table with more use.
(4) How to break through the situation where the communications protocol is separate and realize the standardization and openness of communications.
4 Conclusion Although the price of smart transmitters is slightly higher than that of conventional analog transmitters, its performance-price ratio is beyond the reach of conventional meters. The above examples only summarize several features of the smart transmitter, and there are other advantages that are limited in length and cannot be enumerated. In short, even if there is no corresponding DCS system to match, reasonable choice of smart transmitter, there is no problem of oversizing, it can help automation personnel to improve production efficiency, reduce the workload of the instrument, reduce the spare parts of the instrument, broaden the working ideas, provide solutions to problems New methods and new ideas ultimately increase the automation level of the production process. It is called "the primary application of the smart differential pressure transmitter." The main reason is that the true digital communication function of the smart transmitter is not integrated with the DCS system, fully embodying its comprehensive advantages. Used only as a replacement for conventional transmitters, using some of its features to solve practical problems. For the first time, as a primary experience in the field of smart meter applications dedicated to their peers.

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