What are the disadvantages of thermocouple thermometer?

Friends who like physics probably know the working principle of thermocouple thermometer! But this is a headache for Bian Xiao, because Bian Xiao is blind! Generally speaking, thermocouple thermometer measures temperature through thermoelectric effect. As for the thermocouple, it is actually an energy converter, which converts thermal energy into electrical energy and measures the temperature through its own thermoelectric potential. This measurement method is very extensive and common in industry. Because its components are composed of two metal wires with different materials, it is easy to operate, convenient to use, accurate in measurement and wide in measurement range, so many industrial manufacturing and production cannot do without it.

Although thermocouple thermometers are widely used, in fact! It also has many shortcomings. Let's explain it by Bian Xiao!

1. Complex signal conditioning: In order to convert thermocouple voltage into usable temperature reading, a lot of signal conditioning is needed. For a long time, signal conditioning consumes a lot of design time, and improper processing will introduce errors, resulting in reduced accuracy.

Second, the accuracy is low: except for the inherent inaccuracy of thermocouple caused by metal characteristics, the measurement accuracy of thermocouple can only reach the measurement accuracy of reference junction temperature, generally within 1℃ to 2℃.

3. Corrosion sensitivity: Because the thermocouple is composed of two different metals, under some working conditions, with the passage of time, corrosion may reduce the accuracy. Therefore, it may need protection; And maintenance is essential.

4. Poor noise immunity: When measuring the change of millivolt signal, the noise generated by stray electric field and magnetic field may cause problems. The twisted thermocouple wire is coupled to a magnetic field that may be greatly weakened. Using shielded cable or wiring and protection in metal conduit can reduce electric field coupling. The measuring equipment shall provide hardware or software signal filtering to effectively suppress the power frequency (50HZ/60HZ) and its harmonics.

In addition, the sensitivity is low because the thermoelectric electromotive force is small. Because of its high price and low mechanical strength, it is not suitable for use in reducing atmosphere or metal vapor.

There are still some difficulties in thermocouple measurement. For example, it is not easy to convert the voltage generated by a thermocouple into an accurate temperature reading. There are many reasons: the voltage signal is too weak, the temperature-pressure relationship is nonlinear, and reference junction compensation is needed, and thermocouple may cause grounding problems.

Today, Bian Xiao will introduce you here! Thermocouple thermometers can be used to measure high-temperature areas, such as coking furnaces and steelmaking furnaces, and also to measure low-temperature objects, such as liquid nitrogen and liquid hydrogen. Because thermocouple thermometers also have many shortcomings, more attention should be paid in the process of contact and application! For example, when installing a thermocouple, it should be as vertical as possible to prevent the protective sleeve from being deformed at high temperature. In addition, in order to prevent heat loss, try to install it in the pipeline with protective layer. ? Tubatu Online provides you with "every decoration quotation, 1-4 local decoration companies, 3 sets of decoration design schemes" and the decoration pit avoidance strategy for free! Click this link:/Zhu Ye /zxbj-cszy.php? to8to _ from = SEO _ zhidao _ m _ jiare & amp； Wb, you can get it for free ~