- Nov 07, 2017 -
Pressure transmitter is mainly used for the measurement of parameters such as pressure, flow, level, degree of vacuum and density in industrial process automation control. It is widely used in metallurgy, electric power, chemical industry, coal chemical industry, nuclear power, building materials, shipbuilding, Garbage disposal, highways, urban heating, military, medicine, food and other industries.
Pressure transmitter is a kind of pressure will be detected as the pressure is proportional to the electrical signal, and then amplified, the standard output signal for the control system, secondary instrument provides display, recording, adjustment, measurement, communication and other signals equipment. Pressure transmitter is the core of the pressure sensor and signal processing circuit in two parts.
With the development of computer and electronic technology, pressure transmitter has been rapidly improved in technology, function and performance, and also promoted the development and application of industrial automation.
1 pressure transmitter technology status quo
After years of construction and development, China's instrumentation has been the initial formation of a wide range of product categories, with a certain scale of production and development capabilities of the industrial system, the rapid development of instrumentation in China, the situation is very good, many foreign-funded enterprises and private enterprises have been Rapid development and rise, now has become the main instrument industry. In addition, the state supports and promotes the industrial development of new functional materials and the overall strategic layout in which industrial distribution develops from a lower level to an advanced stage is gradually emerging.
Although China's instrumentation industry has made great progress, it still can not meet the urgent needs of the growing economy in various fields such as national economy, scientific research, national defense construction and social development. Most of our instrumentation products are low-end products, high-precision transmitters rely almost entirely on imports. Our instruments lag behind the international advanced level, the gap is all-round, including product technology gap and the overall strength of the enterprise gap. Mainly reflected in the following areas:
1) Basic material research, not included in national level research projects.
2) The gap between standardized work is large.
3) Technology gap: See Table 1.
4) Industry level gap: SMEs account for the majority, and manufacturing technology is not high.
2 pressure instrument overview
2.1 pressure gauge classification
Since there is pressure in nature and in modern society, we need to measure stress. The pressure gauge is a pressure gauge used to measure.
Pressure gauge according to their measurement accuracy, can be divided into precision pressure gauge, general pressure gauge. Accuracy of precision pressure gauges were 0.1,0.16,0.25,0.4 level; general pressure gauges were 1.0,1.6,2.5,4.0 level of accuracy.
Gauge pressure gauge according to their different instructions, divided into general pressure gauge, absolute pressure gauge, differential pressure gauge. General pressure gauge to atmospheric pressure as a benchmark; absolute pressure gauge absolute zero as a benchmark; differential pressure gauge to measure the difference between the two measured pressure.
Pressure gauge according to its measuring range, divided into vacuum gauge, pressure vacuum gauge, micro pressure gauge, low pressure gauge, pressure gauge and high pressure gauge. Vacuum gauge is used to measure pressure values less than atmospheric pressure; pressure vacuum gauge is used to measure pressure values less than and greater than atmospheric pressure; micro-pressure gauge is used to measure pressure values less than 60,000 Pa; low pressure gauge is used to measure pressure values 0-6 MPa ; Medium pressure gauge is used to measure the pressure value of 10 ~ 60MPa; High pressure gauge is used to measure the pressure value of more than 100MPa.
Pressure transmitter is the most commonly used in industrial practice, a pressure measuring instrument, which is widely used in a variety of industrial automation environment, involving water conservancy and hydropower, railway transportation, intelligent building, production control, aerospace, military, petrochemical, oil wells, electricity , Ships, machine tools, pipes and many other industries.
2.2 pressure transmitter composition and measurement principle
As a measuring instrument converted to electrical signals, Figure 1-2-1 is a basic block diagram of the pressure transmitter: After the pressure sensor detects the pressure, it outputs an electrical signal, which can be either voltage or frequency Or pulse. Signal processing circuit will amplify this signal or plastic, if the smart transmitter will convert this signal into digital, non-linear and temperature compensation, and then converted to analog, sent to the transmitter output part, into 4 ~ 20mA current signal. If non-intelligent transmitter, the analog electrical signal sent directly to the output. The general transmitters are 2-wire meters that use the same 2 wires for power and measurement signal output.
3.Specialized (individualized) demand is more prominent, more broad application areas
With the improvement of the level of industrial automation, various industries, especially the fine chemicals, petroleum and petrochemicals, coal chemical industry's development, the requirements of the transmitter is also getting higher and higher, for different process conditions, to be developed for intelligent transmitters , To solve the pressure, flow, liquid measurement process problems.
Such as: in the coal oil, coal gas technology, need to solve the high temperature, high pressure, hydrogen permeation, solid impurities flushing and clogging problems of the special flange transmitter. In large fertilizer urea synthesis, fine chemicals, need to solve the high temperature, high pressure, strong corrosion, easy crystallization, and high temperature vacuum measurement of special transmitter. In deep-sea oilfields, special pressure transmitters that are resistant to sea water corrosion, high pressure protection grade and high reliability of the sea bottom should be developed to ensure long-term and stable operation of the transmitter in offshore oil exploration. In the liquid, gas measurement, the need for a dedicated multi-parameter smart pressure transmitter to improve the accuracy and reliability of small flow measurement. The company is located in:
The design and manufacture of standardized transmitters have formed a certain industry standard, but the instrumentation industry in our country is facing huge challenges. Only by improving the performance of domestic brands in order to compete with foreign brands have a place.
Aiming at the long service life, stability and reliability of sensor and instrument components in China, there is a big gap between advanced technologies and products in foreign countries, and the reliability design and analysis of component reliability service platforms, sensors and instrumentation components are established. Reliability Test and evaluation; environmental adaptability test technology and simulation; reliability database construction technology, build a unified reliability database, data sharing; reliability screening test and reliability management. A little accumulation, step by step in order to create good future development of the industry.