How to properly use thermocouple temperature sensor - Solutions - Huaqiang

inductance

Thermocouples are an important part of temperature sensors and are very common in automated production. The correct use of thermocouples is directly related to the accuracy of temperature measurement, and secondly, it can save materials and save money. Thermocouple temperature sensor should pay attention to the error caused by the following conditions during use, and minimize the error.

First, due to the error introduced by the installation

The correct installation method for the thermocouple should be 1. The thermocouple should be away from the door and the place where it is heated. The depth of insertion is at least 8 to 10 times the diameter of the protection tube. 2. Avoid strong electric and magnetic fields, and isolate the thermocouple from the power cable. 3. When measuring the gas temperature, it should be installed along the direction of gas reverse flow. 4. The gap between the thermocouple protection tube and the furnace wall hole should be blocked with thermal insulation to prevent air convection and affect its temperature measurement.

Second, the error introduced by thermal inertia

Thermal inertness means that the temperature displayed by the thermocouple temperature sensor lags behind the temperature of the measured object. In order to reduce thermal inertia, a thermocouple with a small time constant should be selected. The time constant is proportional to the diameter of the hot end of the thermocouple, the density of the material and the specific heat, and inversely proportional to the heat transfer coefficient. To reduce the time constant, in addition to increasing the heat transfer coefficient, the most effective way is to minimize the size of the hot end. . In use, it is usually a material with good thermal conductivity, a protective tube with a thin tube wall and a small inner diameter.

Third, the thermal resistance error

The thermal resistance error is caused by infrequent maintenance, such as dust adhering to the surface of the thermocouple, which causes an increase in thermal resistance. The usual practice is to keep the thermocouple protection sleeve clean and wipe it often.

Fourth, the error introduced due to the deterioration of insulation performance

If there is a problem with the thermocouple insulation performance, it will first cause the loss of the thermoelectric potential, and secondly, it will introduce external interference. The error introduced by this is not small. In high temperature applications, there may be a difference in Baidu. Therefore, when selecting materials, materials with good insulation properties should be selected, which can also extend the service life of the thermocouple.