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Working principle of thermocouple

by:JVTIA     2021-01-22

The basic principle of thermocouple temperature measurement is that two conductors of different components form a closed circuit. When there is a temperature gradient at both ends, current will flow through the circuit. At this time, there is an electromotive force-thermoelectromotive force between the two ends. It is the so-called Seebeck effect. Two homogeneous conductors with different compositions are thermoelectrodes, the end with a higher temperature is the working end, the end with a lower temperature is the free end, and the free end is usually at a certain constant temperature. According to the functional relationship between thermoelectromotive force and temperature, a thermocouple index table is made; the index table is obtained when the free end temperature is at 0℃, and different thermocouples have different index tables.


Note on selection of thermocouple materials
Not all materials can form a thermocouple. Generally, the basic requirements for the electrode material of a thermocouple are:
1. Within the temperature measurement range, the thermoelectric properties are stable, do not change with time, have sufficient physical and chemical stability, and are not easy to oxidize or corrode;
2. The temperature coefficient of resistance is small, the conductivity is high, and the specific heat is small;
3. The thermoelectric potential generated in temperature measurement should be large, and the relationship between thermoelectric potential and temperature is linear or close to linear single value function;
4. The material has good reproducibility, high mechanical strength, simple manufacturing process and low price.



Product features of micro thermocouple

The micro thermocouple has many advantages such as flexibility, high pressure resistance, fast thermal response time and durability. It is the same as the industrial assembled thermocouple. It is used as a transmitter to measure temperature, usually with display instruments, recording instruments and electronic regulators. It can be used as a complete set, and can also be used as a temperature sensing element of an assembled thermocouple. It can directly measure the temperature of liquid, steam, gas medium and solid surface in the range of 0~800℃ in the production process of famous species. It is suitable for temperature measurement and control in narrow and curved places.


Thermocouple production standard:

Thermocouple is one of the most commonly used temperature detection sensors in industry, civil use, testing, and scientific research, with high measurement accuracy. The thermocouple is in direct contact with the measured medium and is not affected by the intermediate links, and cannot be replaced by an infrared thermometer. Thermocouples can be continuously measured from -80~+2300℃. Some special thermocouples may have a wider range, but the temperature is too high and not recommended.


Omega thermocouple terminal audit capability

The rail-mounted thermocouple terminal block from the DRTB series from Omega Engineering has a built-in SMP compatible socket, which accepts a female miniature thermocouple connector. The female connector enables you to connect, such as data collection, quality assurance compliance, capability research applications, handheld instrumentation and troubleshooting installation or repair.

The DRTB series terminal blocks come in K type, J, T type, electronic, nitrogen, R/S analysis and U calibration. Its plastic shell is made of gray polyamide 6.6 a UL94V0 rated thermoplastic resin to 85°C. In addition, they are fully enclosed and do not require end plates. The screws and clamps are zinc-plated, providing a maintenance-free connection, both withstand vibration and corrosion.

The junction box of the thermocouple is installed on a standard 35mm DIN rail or 32mm G-rail. The width of the terminal is only 10.7 mm. Each unit is determined and calibrated with positive (+) and negative (-) connections. The wire entry funnel allows fast wire insertion even if twisted wire.
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