Microprocessor-based field smart meters are produced in accordance with the field bus. Similarly, the application of field smart meters also provides a good foundation for field bus development and application and raises new questions for expert research. At this stage, the on-site intelligent instrument, as introduced in related literature, is a compelling transition product due to the incompatibility of communication protocols and the holding point of 4-20mA analog signal transmission of conventional instruments. Really intelligent field instruments that can't really adapt to fieldbuses. It can neither reduce the initial installation cost of the control system, nor can it give full play to its own superior functions, nor can it realize the mutual information exchange and operation between field intelligent instruments.
毕竟代表着新一代变送器的崛起，它采用了当今不少高新技术，如传感技术，微电子数字处理技术等，与常现变送器相比，具有精度高、稳定性好、可靠性高、测量范围宽、量程比大等特定。 However, after all, the intelligent differential pressure transmitter represents the rise of a new generation of transmitters. It uses many high-tech today, such as sensing technology, microelectronic digital processing technology, etc. High accuracy, good stability, high reliability, wide measuring range, large range ratio, etc. Even 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, man-machine dialogue, and online monitoring of various data. Like all smart meters, smart transmitters also have comprehensive self-diagnostics. It can be said that the current smart transmitter is a new type of transmitter that replaces the past and represents the future development of field instruments.
Second, the application of intelligent differential pressure transmitter The following examples of practical applications of smart transmitters, give play to its various characteristics, and solve various problems in process control surveying. It should be pointed out that there are various types of smart transmitters on the market, and the internal functions will have different characteristics. Therefore, the individual examples given in the article may not be general. Please call the readers. 1. Actually verify the original design differential pressure. There is a differential pressure flow meter for the measurement of air flow in the regeneration station of the copper-alkali washing section of a factory. Air is used to adjust the copper ratio after the waste copper liquid is regenerated. The designed differential pressure of this flow meter is 10KPa, but it has not been able to operate normally. On-site operators can only rely on experience to judge and control the air flow, and to accompany the process operation with randomness and blindness; when the door is opened, too much air volume will increase the oxygen content in the system and threaten the system safety. Considering that the air flow is small, the process pipeline is small, and the corresponding art parameters in the original design have deviations, so that the theoretical verification of the original design differential pressure value becomes meaningless. After applying the intelligent differential pressure transmitter, the intelligent differential pressure transmitter has the function of displaying 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 staff, the working differential pressure value and the maximum differential pressure value of the flowmeter were actually measured. Surprisingly, the maximum differential pressure value reached 100KPa, which is 10 times the original design value. It is no wonder that the original differential pressure flowmeter could not operate normally. According to this differential pressure value, the measurement upper limit of the transmitter is modified with an intelligent terminal, and the automatic measurement of air flow is realized, which solves the problem that has not been solved in history and has been troubled for a long time. In the application of differential pressure flowmeters, especially in the measurement of small flow and small pipelines, there may be a series of problems such as detailed process parameters or serious deviations from the actual situation. Causes a serious error in the original differential pressure value of the juice, causing the entire flowmeter to be abnormal. At this time, the use of intelligent differential pressure transmitters can play a role in simplifying and simplifying. It can directly measure the pressure difference before and after the throttling part, and then modify the original design value to solve the difficult problem. 2. Simplify system composition. 流量计的开方环节，简化了测量、控制系统的构成。 The intelligent differential pressure transmitter only needs to obtain the output signal that is related to the square root of the input differential pressure signal through simple settings, so it can be avoided by using the square root of the differential pressure transmitter flowmeter, which simplifies the measurement and control system. Composition. The benefits are self-evident. At the same time, the small signal resection after the prescription is unique. There are two types of small signal resection: one, like an ordinary squarer, complete resection when the output signal is less than the resection point. The second is that when the output signal is smaller than the cut-off point, the output signal has a linear relationship with the input differential pressure signal. The resection points of the two resection methods are continuously adjustable between 0% -20%. The linear resection method is useful for on-site operation when measuring the lower limit flow. 3. Reduce the number of instrument spare parts. For nitrogen companies, the main line of the ammonia synthesis tower's imported hydrogen and fluorine mixed gas flow measurement can be measured with large flow and small flow. The large flow rate is used for the normal production of the synthesis tower, and the small flow rate is used for the heating-up and reduction stage after the catalyst update of the synthesis tower. When using a conventional differential pressure transmitter. In the heating-reduction phase, a small-range differential pressure transmitter (the actual differential pressure value of our factory is KPa) is required to measure and control the safe gas volume (that is, small flow rate) when the electric furnace is warming up; after the heating-reduction phase ends, the synthesis tower is put into operation. In normal production, it needs to be replaced with a large range of differential pressure transmitters (actual differential pressure value is 254KPa). Usually conventional differential pressure transmitters do not have such a large range ratio. For full production needs, the flow measurement In fact, it is equipped with two differential pressure transmitters. The intelligent differential pressure transmitter has a large range ratio, and has self-setting and self-checking capabilities. It can be used to measure the main line flow only in the control room through an intelligent terminal. The small range differential pressure value and a large number of range differential pressure values are modified and completed the same purpose. Avoiding the disassembly and verification of the conventional differential pressure transmitter, reducing the maintenance of the instrument, and reducing the number of spare parts tables. Conventional differential pressure transmitter The range ratio of Yu is not large, like the familiar 1151 differential pressure transmitter. The range ratio is 6: 1, and the range ratio of smart transmitters can reach at least 30; 1. Generally up to 50: 1. Obviously, if you use Smart transmitter as conventional 4-20mA The transmitter's spare parts can greatly reduce the specifications and quantity of the spare instrument. 4. It is convenient for the on-site display instruments of various parameters to be easily set, and the LCD module built in the smart transmitter can display various data. .For example, the pressure receiver can directly display the input pressure and the corresponding unit on the LCD, and the differential pressure receiver can make the flow rate engineering value of the LCD indicating unit self-defined. In some cases, the on-site indicator can be omitted, such as pressure Meters, rotor flow meters, etc. without affecting on-site monitoring and operation. The LCD display module has a forced self-diagnosis display function. Once the measured parameter exceeds the range or the transmitter itself fails, the LCD will display an error code to replace the original set parameter. The display is helpful for timely troubleshooting. If the smart terminal is used, more process information can be read from the transmitter.
Third, the problem that needs to be improved in technology It is also found in use that the smart transmitter still has technical problems that need to be improved.
(1) How to realize the encryption of the transmitter to ensure the authority of various setting data.
(2) How to reduce the power supply requirements of the transmitter during communication. Convenient for on-site debugging and maintenance.
(3) How to separate other information measured by the transmitter, such as the ambient temperature, the static pressure of the process medium, and the differential pressure value, etc., which can be displayed on the smart terminal to achieve a multi-purpose table.
(4) How to break through the fragmented situation in communication protocols and realize the standardization and openness of communication.
Fourth, the conclusion Although the price of the intelligent differential pressure transmitter is slightly higher than the conventional analog transmitter, but its performance-price ratio is beyond the reach of conventional instruments. The above examples summarize only a few features of the smart transmitter. There are other advantages that are limited in space and cannot be listed one by one. In short, even if there is no corresponding DCS system to support it, a reasonable selection of intelligent transmitters does not have the problem of large materials and small use. It can help automatic control personnel improve production efficiency, reduce the workload of instruments, reduce instrument spare parts, broaden working ideas, and provide solutions New methods and new ideas will ultimately improve the automation level of the production process.
的初级应用”，主要原因是未将智能变送器真正意义上的数字通讯功能与DCS系统结合起来，充分体现其综合优势。 The reason why it is called "the primary application of intelligent differential pressure transmitter " is that the digital communication function of the intelligent transmitter in the true sense is not combined with the DCS system, which fully reflects its comprehensive advantages. Only used as a replacement for conventional transmitters, using some of its characteristics to solve problems in actual work. Let's dedicate it to our peers as the primary experience of smart meter application in the field.