Although thermocouple and thermocouple effects are same measuring the temperature of the objects, but their principles and features are different. 1, thermocouple is divided into eight different degree, respectively b, r, s, k, n, e, j and t, its measuring low measurable temperature of minus 270 degrees Celsius, up to 1800 degrees c, b, r, s belong to platinum series thermocouple, because platinum are precious metals, so the thermocouple is also known as precious metals, and the remaining few called cheap metal thermocouple. 2, commonly used thermocouple pt100, pt10, cu50, cu100, platinum thermocouple temperature measurement range is generally 200 - below zero 800 degrees Celsius, copper thermocouple to minus 40 to 140 degrees Celsius; 3, different application temperature range: thermocouple used in 300 degrees commonly the following, thermocouples are used for more than 300 degrees; 4, material: thermocouple is commonly made of pure metal resistance wire, thermocouple is usually two different materials of metal; 5, different signal: thermocouple is the resistance value and temperature, thermocouple is millivolt level signals and measuring temperature corresponding; 6, connection ( Compensation) In a different way: thermocouple need dedicated two compensation wire lead to signal wire, thermocouple is usually three copper wires. Commonly used in low temperature zone thermocouple is a kind of temperature detector. Thermocouple temperature measurement is based on the metal conductor resistance value increases with the increase of the temperature of the properties for temperature measurement. Its main characteristic is high accuracy, stable performance. The platinum thermocouple measuring accuracy is high, it is not only widely used in industrial temperature measurement, and is made into standard benchmark instrument. Thermocouples are mostly made of pure metal materials, the application is a lot of platinum and copper, in addition, now began to use the materials such as nickel, manganese and rhodium thermocouple. Metal thermocouple commonly used thermal material sort is more, the most commonly used is a platinum wire. Industrial measurement with metal material in addition to the platinum wire, thermocouple as well as copper, nickel, iron, iron - Nickel, etc. The main species from the thermocouple temperature measurement principle of thermocouple, measured the change in temperature is directly measured by thermocouple resistance change, therefore, of the thermocouple lead wire and other wire resistance change will affect temperature measurement. Thermocouple is by thermal components ( The resistor body) , wire, insulation materials, stainless steel casing combination solid body, its diameter is commonly phi - 2 Phi mm phi 8 mm, a small coke. Compared with conventional type thermocouple, it has the following advantages: 1, small volume, no internal air gap, thermal inertia, small measuring hysteresis; 2, good mechanical properties and resistance to vibration and impact resistant; 3, can bend, easy to install; 4, long service life. Capillary thermocouple ends thermocouple temperature sensing element resistance wire winding by special processing, close to the face in the thermometer. Compared with general axial thermocouple, it can reflect more correctly and quickly end face of the actual temperature being measured, is suitable for measuring temperature bearing and other parts of the face. Flameproof thermocouple junction box flameproof thermocouple with special structure, its shell internal explosive mixed gas by affected by sparks or electric arc explosion limit within the junction box, that wouldn't make production field explosion. Flameproof thermocouple can be used in the Bla B3c level zone with explosion danger place temperature measurement.