1. Platinum platinum rhodium thermocouple (s type) graduation grade lb-3 industrial thermocouple wire: Φ 0.5mm, laboratory use can be finer. Cathode: platinum rhodium alloy wire, with 90% platinum and 10% rhodium (weight ratio) smelting. Negative electrode: platinum wire. Measurement temperature: long term: 1300 ℃, short term: 1600 ℃.
characteristic:
(1) It can be made into standard thermocouple or reference thermocouple. Purpose: laboratory or calibration of other thermocouples.
(2) The measurement temperature is high, which is generally used to measure the high temperature above 1000 ℃.
(3) It is easy to be eroded in high-temperature reducing gas (such as CO, H2, etc.) and needs to be protected.
(4) The material is precious metal and the cost is high.
(5) The thermoelectric potential is weak.
2. Pt Rh 30 Pt Rh thermocouple (type b) is LL-2 positive electrode: Pt Rh alloy (made by smelting 70% Pt and 30% RH). Platinum (6%) is used as anode. Measurement temperature: 1600 ℃ in the long term and 1800 ℃ in the short term.
characteristic:
(1) The material performance is stable and the measurement accuracy is high.
(2) It is easy to be eroded in reducing gas.
(3) The low temperature thermoelectric potential is very small, and there is no compensation when the cold end temperature is below 50 ℃.
(4) High cost.
3. Several thermocouples with special application
(1) It can measure high temperature up to 2100 ℃ in oxidizing atmosphere.
(2) Tungsten rhenium thermocouple was developed in 1960s. It is a good high temperature thermocouple at present. It can be used in vacuum inert gas medium or hydrogen medium, but its high temperature oxygen resistance is poor. The working temperature range of domestic w-re-20 thermocouple is 300-2000 ℃, and the graduation accuracy is 1%.
(3) Au Fe Ni Cr thermocouples are mainly used for low temperature measurement. They can be used in the range of 2-273k. The sensitivity is about 10 μ V / ℃.
(4) Palladium platinum iridium 15 thermocouple is a kind of thermocouple with high output performance. Its thermoelectric potential is 47.255mv at 1398 ℃, which is three times higher than that of platinum platinum Platinum Rhodium 10 thermocouple at the same temperature. Therefore, it can be used with indicator instruments with lower sensitivity and is often used in aviation industry.
(5) It has good linearity and low price. It can be used in reducing medium below 800 ℃. The main disadvantage is that iron is easy to oxidize, and the anti rust ability can be improved by bluing treatment.
(6) The thermoelectric potential of thermocouple MK is slightly higher than that of Ni Cr Ni Si thermocouple, which is about 43 μ V / ℃. It has good reproducibility, good stability, high precision and low price. The disadvantage is that copper is easy to oxidize, so it is widely used in low temperature laboratory measurement from 20K to 473k.
4. Zirconium diboride composite ceramic thermocouple has a temperature measurement accuracy of ± 2 ℃ at 200-1900 ℃, and can be used in vacuum or oxidation environment with an error of ± 10 ℃ at 1900-2200 ℃. But it has not been widely recognized by the market.
On 2018-08-08 11:45:46
