The most detailed thermocouple selection rules

When actual temperature measurement, by the side of the object is extremely complex, should be familiar with the object to be tested, grasp the thermocouple on the basis of the features, according to the measurement requirements, the use of the environment, such as temperature correctly choose thermocouple.

one, by using temperature choose

when t< More than 1000 ℃, choose cheap metal thermocouple, such as K type thermocouple. Its characteristic is to use a wide temperature range and high temperature performance is stable. When t = - 200 a 300 ℃ when, had better choose T thermocouple, it is a cheap metal thermocouple in the highest accuracy; E can choose the type thermocouple, it is a cheap metal thermoelectric potential change rate is the largest, the highest sensitivity. When t = 1000 - a - 1400 ℃, choose more R, S type thermocouple. When t< At 1300 ℃, can choose N or K type thermocouple. When t = 1400 - a - 1800 ℃, choose B type thermocouple. When t< 1600 ℃, the short-term available S type and R type thermocouple. When t> At 1800 ℃, often choose tungsten zinc thermocouple.

2, according to the measured medium choose

1, oxidizing atmosphere

when t< More than 1300 ℃, the selection of N and K type thermocouple, because they are cheap metal thermocouple oxidation resistance in the strongest; When t> When 1300 ℃, choose platinum basking thermocouple.

2, vacuum, reducing atmosphere

when t< At 950 ℃, can choose J type thermocouple, it can work under oxidizing atmosphere. And can work under reducing atmosphere; When t> At 1600 ℃, should choose tungsten-rhenium thermocouples.

3, choose according to the influence of the temperature of the cold end

when t< At 1000 ℃, can choose to drill a nickel aluminum thermocouple, the cold end temperature in 0 300 ℃, can ignore its influence, it is often used in aircraft exhaust exhaust temperature measuring arms; When t> At 1000 ℃, often choose B type thermocouple, can generally be ignored the influence of the temperature of the cold end. 1) According to the diameter of the electrode and the choice of the length of the hot electrode diameter and length of selection is the hot electrode materials, resistivity, temperature measurement range and the price of mechanical strength. For the rapid response, must choose fine wire electrode diameter. Test site end is smaller, the more sensitive. The faster response speed, the greater the resistance but also. If the hot electrode diameter is choose carefully, can make the test address line resistance increased.