S type thermocouple deficiency is thermoelectric potential, thermoelectric potential rate is small, low sensitivity and mechanical strength under high temperature to drop, is sensitive to pollution, precious metal materials is expensive, and one-time investment is larger. （ K type thermocouple) Nickel chrome - Nickel silicon thermocouple nickel chrome - Nickel silicon thermocouple ( K type thermocouple) Is the use of inexpensive metal thermocouple, its dosage is the sum total of other thermocouple. The anode ( KP） In the name of the chemical composition is: Ni: Cr = 90:10, the cathode ( KN) In the name of the chemical composition is: Ni: Si = 97:3, minus its working temperature 200~1300℃。 K type thermocouple has advantages of good linearity, thermoelectric emfs, high sensitivity, good stability and uniformity, the oxidation resistance is strong, the advantages of cheap, can be used for oxidizing inert atmosphere. Widely adopted for the user. K type thermocouple cannot directly at high temperature for sulfur, reducing or reduction, oxidation atmosphere and vacuum alternately, also not recommended for people with weak oxidizing atmosphere. （ T thermocouple) Copper - Copper nickel thermocouple copper - Copper and nickel thermocouple ( T thermocouple) Also known as copper - Constantan thermocouple, is also a kind of measuring thermocouple of cheap metal at low temperature. It's the positive ( TP） Is pure copper, anode ( TN） For copper and nickel alloy, often as a constantan, chromium and nickel - it - constantan constantan EN general, and iron Constantan constantan Jacqueline Nottingham not general, although they are called constantan, copper - The lid of the copper and nickel thermocouple temperature range of measurement for - 200~350℃。 T thermocouple has advantages of good linearity, thermoelectric emfs is bigger, high sensitivity, good stability and uniformity, the advantages of cheap, especially in - 200 to 0 ℃ temperature zone, better stability and stability can be less than + / - 3 mu in V, the low temperature test can be used as second class standard value transmit. in at low temperature. T thermocouple of the anode copper poor oxidation resistance at high temperature, so the temperature limit is restricted.