Fe-CuNi thermocouple (type J) is also named Fe- Constantan thermocouple. The positive leg Fe(JP) is made by pure Iron, and the main chemical composition of negative leg Constantan (JN) is Cu: Ni'e 55%; 45%. Although they are all called Constantan, JN does not give the same EMF output curve as EN and TN, it cannot be instead by other Constantan. The operating temperature range of type J thermocouple is -210~1200℃, but it is usually used in the temperature range 0~750℃c due to embrittlement of Iron. Type J thermocouple has good resistance to oxidation and high EMF output against Platinum 67, with good temperature accuracy, sensitivity and stability. It is recommended for vacuum, oxidizing, reducing or inert atmospheres, but it can not be used in sulphurous atmosphere above 500℃.

NiCr-NiSi(Type K) thermocouple finds the widest use in all basemetal thermocouple, at temperature above 500℃。The main chemical composition of positive leg NiCr (KP) are Ni~90% and Cr~10%; negative leg NiSi (KN) are Ni×97% and Cr~3%. The operating temperature range is -200~1300℃(for short term) and 0~1100℃( for long term)。 Type K thermocouple has strong resistance to oxidation than other base metal thermocouples. It has high EMF against Platinum 67, excellent temperature accuracy, sensitivity and stability, with a low cost. It is recommended for oxidizing or inert atmospheres, but cannot be used directly in the following cases: (1) Alternatively oxidizing and reducing atmosphere, (2) Atmosphere with sulphur gases (3) Long time in vacuum (4) Low oxidizing atmosphere such as hydrogen and carbon monoxide atmosphere

Cu-CuNi thermocouple (type T) is also named Cu- Constantan thermocouple. The positive leg Cu(TP) is made by pure Copper, and the main chemical composition of negative leg Constantan (TN) is Cu: Niz 55%: 45%. Although EN, TN, JN are all called Constantan, TN and EN do not give the same EMF output curve as JN. EN and TN are able to interchange but they are not interchangeable with JN. The operating temperature range of type T thermocouple is -200~350℃, Due to the low resistance of oxidation that Copper has, it is not advisable to go beyond that range. Type T thermocouple has good resistance to oxidation, high EMF output, with good temperature accuracy, sensitivity and stability. In the temperature range -200~0℃, it has better property, the year stability is less than ±3μV.

NiCrSi-NiSiMg(Type N) thermocouple is the latest base metal thermocouple, developed to improve the drawbacks that type K thermocouple has. The main chemical composition of positive leg NiCrSi(NP) is Ni: Cr. Si~84.4:14.2: 1.4; negative leg NiSiMg (NN) is Ni: Si: Mg~95.5: 4.4:0.1. Type N thermocouple also be used in the similar atmospheres that type K works, and the operating temperature range is -200~1300℃C。 Type N thermocouple improves the EMF drift and short term EMF change, compared to type K thermocouple, and has a longer life than type K thermocouple. Therefore, in the industries where temperature control and measurement are especially critical, type N thermocouple has more advantages than other thermocouple as it has long life and stable thermal EMF.

NiCr- CuNi thermocouple (type E) is also named NiCr- Constantan thermocouple. The main chemical composition of positive leg NiCr (EP) is Ni: Cr~90:10; negative leg Constantan (EN) is Cu: Nize 55%, 45%. Although EN, TN, JN are all called Constantan, EN and TN don not give the same EMF output curve as JN. EN and TN are able to interchange but they are not interchangeable with JN. The operating temperature range of type E thermocouple is -200~900℃。 Type E thermocouple has the largest EMF output and highest sensitivity, so it is ideal for measuring small temperature change. It also has good stability in the low temperature range up to 300℃, and good property of anti-corrosion in humidity atmosphere. It is recommended for oxidizing or inert atmospheres, but cannot be used directly in reducing atmosphere and atmosphere with sulphur gases.