The thermocouple is the most accurate and most economical product in the development of measurement sensors. Therefore, it has become the most widely used type of temperature measuring element. It directly measures temperature. The shapes of various thermocouples are often very different due to needs, but their basic structures are roughly the same. They usually consist of main parts such as hot electrodes, insulating protection tubes and junction boxes, and are usually combined with display instruments, recording instruments and electronic regulators. Supporting the use of. A thermocouple measures the temperature difference between its hot and cold ends. In order to obtain the absolute temperature at the hot-junction sensing point, the cold-junction temperature must be measured and the thermocouple output adjusted accordingly. Now, the cold junction located at the input of the thermocouple signal processing unit is kept at the same temperature, usually by a sheet of material with high thermal conductivity. Thermal conductivity/copper is an ideal material. Input connections must be electrically isolated and thermally connected to the chip. The entire signal processing unit should ideally be in this same temperature environment. The stability of thermocouples varies depending on the operating temperature and climate. So how to control the stability of thermocouples? For the same type of sensor, the maximum operating temperature of a type thermocouple also changes due to different diameters. Type thermocouples with the same diameter also have great differences in stability due to different structures. When selecting a thermocouple, it must be based on the use. The conditions consider the anti-vibration performance of the atmosphere such as the common temperature and the maximum operating temperature oxidation and reduction. For assembled thermocouples, the influence of the atmosphere first depends on the protective tube material and the thermocouple structure. Therefore, be familiar with the physics of various protective tube materials. , chemical properties are very necessary. For example, in the powder metallurgy industry, molybdenum tubes are commonly used as thermocouple protection tubes. In an atmosphere of 10 degrees Celsius, the use effect is better. However, in an oxidizing atmosphere, molybdenum tubes will deteriorate in a short time. Corroded by oxidation.
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