How to choose the correct thermocouple specifications

How to choose the correct thermocouple specifications

The choice of thermocouple specifications should be based on the temperature range of use, the required accuracy, the atmosphere of use, the performance of the object to be measured, response time and economic benefits.

First, thermocouple specification measurement accuracy and temperature measurement range selection

When the temperature is between 1300 and 1800 °C and the accuracy is relatively high, the type B thermocouple is generally used. The accuracy is not high. The atmosphere allows the use of tungsten-rhodium thermocouple specifications. Above 1800 °C, tungsten-rhodium thermocouple specifications are generally used. The temperature is 1000~1300°C, and the required accuracy is higher. S-type thermocouple specifications and N-type thermocouple specifications are available. Below 1000°C, K-type thermocouple specifications and N-type thermocouple specifications are generally used. Below 400°C, E is generally used. Type thermocouple specifications; T-type galvanic couples are generally used for measurement at 250 ° C and negative temperature. T-type thermocouples are stable and have high precision at low temperatures.

Second, the choice of atmosphere for thermocouple specifications

S-type, B-type, and K-type thermocouples are suitable for use in strong oxidation and weak reducing atmospheres. J-type and T-type thermocouples are suitable for weak oxidation and reducing atmospheres, if a gas-tight protective tube is used. The requirements for the atmosphere are not too strict.

Third, thermocouple specification durability and thermal response selection

Thermocouples with large wire diameters have good durability, but the response is slower. For thermocouples with large heat capacity, the response is slow. When measuring the temperature of a large gradient, the temperature control is poor in the case of temperature control. Requires a fast response time and requires a certain degree of durability.

Fourth, the nature and state of the thermocouple specification measurement object selection of thermocouple specifications

The temperature measurement requirements of moving objects, vibrating objects, and high-pressure vessels are high. The atmosphere with chemical pollution requires a protective tube. In the case of electrical interference, the insulation is required to be relatively high. Selection process: model - indexing number - explosion-proof grade - accuracy grade - mounting and fixing form - protection tube material - length or insertion depth