Based on the analysis of the product samples of Omega, JMS and other companies in the United States, this paper believes that the sensor brand can have two modes: "large and complete" and "small and special". At present, "small and special" is the development direction of domestic temperature instrument enterprises. In order to keep a close eye on the development trend of the instrument in China, the author has been paying close attention to the development trend of the instrument in the world. With the help of Omega and JMS products samples, the author summarizes some opinions.
OMEGA At the beginning of 1990, only temperature, pressure and strain, flow and liquid level and data storage products were produced by the company. In 2004, there were temperature, pressure, strain and force, flow and liquid level, transmitter, data storage, military products for land, sea, air and space. At present, it has established branches in the Netherlands, Canada, Czech Republic, France, Germany, Mexico and the United Kingdom A large and complete instrument enterprise is a model of large and complete. However, in order to develop China's temperature instrument industry, although it is impossible to create a transnational super large temperature instrument enterprise for the time being, the state should advocate cross regional and cross industry joint reorganization, and establish a large and comprehensive temperature instrument enterprise in China as soon as possible, so as to compete with the international large enterprises.
Namnak company is a company specialized in thermocouple temperature measurement products. Its slogan is "the best in the field of temperature measurement". The characteristic product is thermocouple with W-coated Mo protection tube. Mo is usually used as thermocouple protection tube and tungsten rhenium couple is used to measure temperature in high temperature furnace above 1600 ℃ with graphite as lining or heating body. Due to the carbon corrosion at high temperature, Mo tubes are rapidly carbonized and crystallized into pores, and then the grain growth of wre couple occurs. Namnak has such technology that coating Mo tube with a layer of W can minimize the carbonization degree of Mo tube and greatly extend the life of thermocouple. Field test shows that wre thermocouple with W-coated protective tube can be used continuously for 2 months at 2000 ℃, and the life without w coating is only a few hours.
The temperature measurement products of JMS company in Southeast America launched thermocouple type thermal cable in 1990. At that time, the temperature measurement range was - 29 ℃ ~ + 900 ℃, type E, accuracy ± 14 ℃, diameter of wire Φ 2.35-4.80mm, length up to 150m. Thermocouple is a traditional temperature sensor, which is widely used. In recent years, a new temperature measurement technology has been developed on this basis, which has a unique application in fire accident early warning. This new type of temperature sensor is called special temperature sensing cable, also known as continuous thermocouple or heat seeking thermocouple.
The thermal cable uses the thermoelectric effect of thermocouple, but the temperature is not measured at the end of the thermocouple, but at the highest temperature point along the length of the thermal electrode. Because of its unique function, it was initially laid in the cabin of aircraft carrier and destroyer and military aircraft by developed countries as high-precision technology products. At present, it has been widely used in various fields to prevent and reduce accidents and losses caused by "overheating".
Thermal cable is composed of thermal electrode, isolation material and protective tube. Thermoelectric electrode is a pair of parallel wires separated from each other at a certain distance. The graduation number and material of the electrode are similar to those of the standard thermocouple. One of T, J, e, K, s can be selected randomly. The relationship between thermoelectric potential and temperature of thermal sensitive cable is different with different materials. The isolation material tightly filled between thermoelectric electrodes is a kind of thermistor material with negative temperature coefficient (NTC) made by special technology. It is an insulator with high resistance at low temperature. With the increase of temperature, the resistance decreases sharply. Thermistor material is the key to manufacture thermal cable. Different negative temperature coefficient thermistor materials have been used as isolation materials. At present, there are several kinds of thermal cables made of different negative temperature coefficient thermistor materials in the market, and the outer layer is the armored metal protective tube.
The structure of the thermal cable is simple: no external power supply is needed. Strong and durable: armored structure, not only has good toughness, but also has enough strength, can be bent when installed. Gradable: the relationship between thermoelectric EMF and temperature of thermal sensitive cable can refer to the graduation table of standard thermocouple, without field calibration. Strong compatibility: it can be compatible with most current analog instruments and digital thermometers. The thermal cable signal can also be converted into standard signal by temperature transmitter.
The JMS sample also introduces SiC protective tube, carbon bonded SiC protective tube, recrystallized SiC protective tube and other special purpose protective tubes, and introduces the LT-1 cermet protective tube (cr-al2o3) of American carbide company (UCAR) in detail, and introduces the applicable environment and industry of LT-1 protection tube.
The patented t-5590 and t-50230 W-Re thermocouples introduced in the 1991 sample of ARI company in the United States are solid composite tube type wre thermocouples which can be used at high temperature of 7 MPa and 1600 ℃. In this way, it is possible that wre 5 / 26 thermocouple wire only contacts with H2, which solves the problem of oxidation resistance of W-Re thermocouple.
Companies such as namnak and JMS are not big compared with Omega in terms of instruments. However, they all have their own characteristics and compete with large companies, providing a broad space for their own existence and development. Overall view of China's Temperature sensor With the instrument industry, no one can compete with the large and complete Omega company. It is planned and operated by the superior management department and elites to cultivate China's large and comprehensive instrument enterprises by means of establishment and holding shares. So the formation and development of small and special enterprises can be realized by every enterprise leader. To this end, we must closely track the most advanced technology and products in the world and make them serve China. All these "small and special" processes are closely related to the accumulation of theory and practice. In order to systematize and theorize the above ideas. The instrument of our country, the appearance of the international market development, hope to better meet the needs of domestic and international market development.