Thermocouple
Thermocouple Thermometer is a pyrometer metallurgical industry widely used. The thermocouple pyrometer consists of a thermocouple and a millivoltmeter. It has a wide temperature range, simple structure, easy to use and accurate measurement.
First, the working principle of thermocouple Thermocouple pyrometer is composed of two different metal conductor wires A, B, see the figure below. The two conductors of A and B are welded together at one end. When the solder joints of the two wires are heated, a potential difference is generated at the other end of the two wires, and a current is passed therethrough. This phenomenon is called thermoelectric potential. When the heated end is heated, the potential difference is larger. A and B in the figure are called hot electrodes, and the contacts T are usually joined by welding. When measuring temperature, place it in the temperature measurement location, called the working end, and the end point T. Call it the free end and ask it to stay at a constant temperature. For a certain hot electrode material, the thermoelectric potential is only related to the temperature of the two end points, regardless of the length and thickness of the electrode. The thermal electrode of the same material has the same relationship between temperature and potential.
Thermocouple type names often named electrode material, even usual electricity "platinum and rhodium - platinum" thermocouple, "nickel-chromium - nickel silicon" thermocouple.
In order to prevent chemical damage or mechanical damage to the hot electrode, the thermocouple should be placed in the protective tube after the insulating tube is placed. The type of thermocouple is shown in the table below.
Type of ordinary thermocouple | ||||||
Thermocouple name | Index number | Hot electrode | Operating temperature range | Scope of use | ||
polarity | Identification | chemical composition | °C | |||
Platinum rhodium 10-platinum (platinum rhodium) | LB-3 | positive | Harder | Pt6%-Rh10% | long  short term |  Suitable for use in oxidizing atmospheres, not suitable for reducing atmospheres |
negative | soft | Pt100% | 1300-1600 | |||
　 | 　 | 　 | 　 | 　 | 　 | 　 |
Platinum rhodium 30-platinum      铑6 (double platinum 铑) | LL-2 | positive | Harder | Pt70%, Rh30% | long  short term | with   on |
negative | soft | Pt94%, Rh6% | 1600-1800 | |||
　 | 　 | 　 | 　 | 　 | 　 | 　 |
Nickel-chromium-nickel silicon (nickel-chromium-nickel silicon) | EV-2 | positive | Do not | Cr9-10% | long  Short-term 600  800 |  Suitable for use in neutral and oxidizing atmospheres |
Dear | SiO.4% | |||||
magnetic | Ni90% | |||||
　 | 　 | 　 | ||||
negative | a little | Si2.5-3% | ||||
Dear | Co≤0.6% | |||||
magnetic | Ni97% | |||||
　 | 　 | 　 | 　 | 　 | 　 | 　 |
Nickel chrome - copper | FA-2 | positive | color | Cr9-10% | long  Short-term 600  800 |  Suitable for use in reducing atmosphere |
More | Si0.4% | |||||
dark | Ni90% | |||||
　 | 　 | 　 | ||||
negative | silver | 　 | ||||
White | Cu56-57% | |||||
color | Ni43-44% | |||||
   Third, the construction of thermocouple
The construction of the thermocouple, including the four parts, is shown in the figure below.
Stainless Steel Double Ferrule Fitting
DOUBLE FERRULE COMPRESSION FITTING,ss Double Ferrule Fitting
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