At present, high stability of pressure, differential pressure transmitter used more and more important in the field of automation, stability in China's development with high pressure transmitter local transmitter manufacturing enterprises are facing a very serious problem. But through practice shows that using foreign technology can choose from super stability principle of monocrystalline silicon chips, super stability of monocrystalline silicon wafer stress free packaging, elimination of hysterisis error, abate and compensation of static error, instrument range than the broadening of special treatment, the liquid surface as well as ultra high temperature measurement, and many other technical breakthrough, can significantly improve stability of high pressure, differential pressure transmitter, level of whole performance, accuracy and reliability. In order to make up the monopoly and impact of foreign high-end transmitters on China market.
As a high precision field measuring instrument, pressure transmitter and differential pressure transmitter are very common and significant in the field of automation. It has been widely used in most important industries, such as thermal power generation, nuclear power, petroleum smelting, chemical industry, steel, paper making, pharmaceutical, food, cement manufacturing and other fields. In a broad range of applications, however, the domestic research and development and manufacture of high-end pressure transmitter is very scarce, and almost entirely by the United States, Japan, Germany, Switzerland and other industrial developed countries have dominated the pressure transmitter. This is a huge safety hazard for China's rapidly developing national economy. Therefore, it is more and more important to utilize foreign technology research and development and scale production to have high stability pressure and differential pressure transmitter. MaiDeSheng electric (China) co., LTD. Is the use of foreign advanced technology, through introducing and learning from the United States, and by adapting to the characteristics of localization of production and research and development and large-scale production validation, finally formed a monocrystalline silicon resistance principle of high pressure, differential pressure transmitter scale production line.
The present situation of high stability pressure and differential pressure transmitter is analyzed
The current high stability pressure and differential pressure transmitter in the Chinese market are divided into three types and principles. The first is a series of 1151 series and 3051C/S series of metal capacitance pressure and differential pressure transmitter, which are developed by American manufacturers and produced in Beijing, China. Its working principle is: the external pressure differential relay to metal capacitance plate, internal displacement occurs when the plate after the changes of electric capacity, namely, the change of capacitance through collection, magnified electronic circuit and the software compensation after processing, get the pressure signal of linear output.
1, 3051 and 1151 series capacitance sensor technology introduced into China by the 80 s, in the domestic large-scale counterfeit and promotion, to 2016 domestic manufacturers of generic reached nearly hundred, typical domestic manufacturers have Shanghai, xian, Beijing, chongqing and the ministry of nuclear industry instrument co., LTD. Domestic instrument manufacturer, after many years of research and exploration, and the most manufacturers began in the early 21st century will be 1151 transmitter have been dealt with miniaturization, shrink sharply, gradually shift to digital circuit and analog circuit, finally realizes the accuracy level from 0.5 to 0.5 on the Richter scale are unlikely. But this improvement without fundamentally changing the structure of the sensor, still have considerable limitations, thus improved the accuracy and long-term stability, EMC performance, static pressure, temperature properties are compared with the original 3051 c/S still a gap. Eventually, domestic transmitters still lag far behind developed countries.
However, the American 3051C/S series transmitter has been revolutionized on the basis of 1151, which has realized substantial improvement in structure isolation, suspension and circuit reliability improvement. The degree of accuracy is achieved at the level of 0.05. However, the 3051 c/S technical difficulty and technical barriers brought by the pressure transmitter, cannot effectively by Chinese local enterprises breakthrough, so almost all of China's manufacturers have abandoned the capacitive transducer further exploration and research.
2. The single crystal silicon pressure transmitter and differential pressure transmitter developed and manufactured by the Japanese manufacturer, the representative model is the yokogawa EJA and the EJX series. Its working principle is: the external pressure difference to the internal monocrystalline silicon resonant beam, the resonance beam under the action of pressure produced a pair of differential frequency signal, with pressure changes will be the differential frequency signal through the collection, magnified electronic circuit and the software compensation after processing, get the pressure signal of linear output.
A series of single-crystal silicon resonant transmitters in henghe EJA series has some advantages over the manufacturing cost control in the production process of the capacitive sensor. Main advantage in temperature and static pressure compensation, namely: the double resonance circuit of the original differential signal output, and the differential signal is not affected by temperature and static pressure, so for the transmitter temperature compensation of the late and static pressure compensation process links such as simple operation. Its final accuracy rating reached 0.065, slightly less than the rosemount 3051C/S series. But with the mass production of monocrystalline silicon resonant beam chip technology is yokogawa company monopoly, the single crystal silicon resonant beam chip brought about by the technical difficulty and technical barriers, also cannot effectively local Chinese enterprises breakthrough, so almost all of China's manufacturers have abandoned the monocrystalline silicon resonant transmitter further exploration and research.
3. Single crystal silicon resistance pressure and differential pressure transmitter represented by MADSHEN international corporation, Germany and Switzerland. Its working principle is: the external pressure differential is passed to the piezoresistive effect of monocrystalline silicon full dynamic within the wheatstone bridge, hui, a bridge under the action of pressure to produce a voltage signal output, follow the pressure changes the voltage signal collection, amplified by electronic circuit and the software compensation after processing, get the pressure signal of linear output.
This kind of monocrystalline silicon resistive sensor output high sensitivity, large amount of signal and return difference, and circuit design is simple, reliable and so on the international more transmitter manufacturers preferred using this solution to research and development and manufacture of high-end transmitter. But compared with the above mentioned metal capacitive sensor and single crystal silicon resonant sensor, the application of single crystal silicon resistance chip has a special process requirement. It mainly shows the non-stress encapsulation technology of silicon chip and the one-way overload protection technology of silicon thin film. These two application technology in firmly in the hands of western developed countries by 2000, from 2013 years later, the MaiDeSheng electric (China) co., LTD. Through technical cooperation MADSHEN international companies from the United States, introduction, and then research and development, eventually fully mastered a number of related technologies, thus realize the stability of high silicon pressure, differential pressure transmitter in the domestic large-scale manufacturing, MDSGP100 series and MDSDP series high stability of monocrystalline silicon transmitter accuracy theory up to 0.05 grade, normal can reach 0.075, well-known brands abroad completely achieve even more than the above of the transmitter.