1, Reasons for errors
1. The impact of thermocouple accuracy on measurement errors. This refers to the thermoelectric characteristics, stability, and uniformity of thermocouples.
2. The impact of the indexing characteristics of display instruments and measurement circuits on measurement accuracy.
3. After laying thermocouples on the tested surface, the original temperature field at the tested location was changed. At this point, the temperature indicated by the surface thermocouple is no longer equal to the temperature when the thermocouple was not installed. The error caused by thermal conductivity after laying surface thermocouples is called "thermal conductivity error". It should be emphasized that the accuracy of the thermocouple itself produces much smaller errors compared to thermal conductivity errors. As long as high-quality thermoelectric electrode materials are selected, the thermoelectric characteristics are stable, and the thermocouple and instrument are properly matched, the errors caused by the accuracy of the thermocouple itself can generally be ignored. However, thermal conductivity errors are difficult to avoid and are crucial for surface temperature measurement.
4. If the surface temperature of the measured object is in a changing state, the error caused by the dynamic response lag of the thermocouple to temperature is called the "dynamic response error". After installing a thermocouple on the tested surface, the surrounding environment will also generate radiation heat transfer on the thermoelectric electrode. For example, the difference in surface blackness between the tested object and the thermoelectric electrode generates radiative heat transfer. This type of error is called the "radiation heat transfer error"
2, Errors caused by improper installation and laying methods.
In summary, the measurement error of surface wear-resistant thermocouples is generally caused by the six factors mentioned above. To determine the total measurement error, further error analysis is necessary, which can be determined through experiments and calculations.

3, Measures and methods to reduce measurement errors
1. Choose thermoelectric electrode materials with small thermal conductivity and fine diameter as much as possible under the conditions of mechanical strength. The diameter of the thermoelectric electrode is usually selected from 0.2 to 0.5 millimeters.
2. When laying surface thermocouples, the interference of convection should be eliminated as much as possible. For example, when there is flowing gas on the tested surface, if conditions permit, the thermocouple can be buried. But it is important to note that the groove size should be as small as possible, and after embedding, the surface of the filling material should be polished to be level with the measured surface.
3. During installation, try not to damage the temperature field of the tested surface and the geometric shape of the tested object.
4. The dynamic response of the selected surface thermocouple is better during changes in working conditions and instantaneous measurements.
5. Isothermal laying can effectively reduce thermal conductivity errors. The thermoelectric electrode behind the measuring end should be laid along the measured surface for a length of at least 50 times the diameter of the thermoelectric electrode. The thermoelectric insulation along the tested surface should be thin and the material should have good thermal conductivity to enhance the thermal conductivity between the tested surface and the thermoelectric electrode. After the thermoelectric electrode causes the measured surface, the insulation layer of the thermoelectric electrode needs to be thicker and well insulated to reduce the heat dissipation of the thermoelectric electrode towards the gas. If the resistance of the thermocouple measurement circuit is too large, the method of overlapping thick and thin thermoelectric electrodes can be adopted. When selecting the overlapping of thick and thin thermoelectric electrodes, attention should be paid to the consistency of thermoelectric characteristics as much as possible.
6. When measuring surface temperature, we always hope for high accuracy. In order to reduce measurement errors, reasonable measures can be taken according to actual working conditions to obtain satisfactory measurement results.
7. The measuring end of the surface thermocouple should have good thermal contact with the measured surface, and the contact method should be welding (referring to welding allowed on the measured surface). Welding points should not have slag inclusions or porous sponge like structures. The welding points should be small while ensuring sufficient strength. To enhance the welding strength of the thermocouple measurement end, the welding part of the thermoelectric electrode can be slightly biased.
8. The measuring end of the pressure spring thermocouple should be as close as possible to the measured surface. For spherical measuring ends, the measuring end can be flattened. When the thermal conductivity of the tested object is very low, a collector plate with good thermal conductivity can be used.
9. Thermoelectric electrode materials should have good thermoelectric properties, stability, and uniformity. Before production, the thermoelectric electrode material should be calibrated to ensure good and reliable performance.