Calculation method for excessive temperature of standard thermocouples

1. Overview
Excessive temperature refers to the temperature that exceeds the design temperature range of a thermocouple, which can cause changes in the physical properties of the thermocouple material, thereby affecting the accuracy of temperature measurement. The calculation method for excessive temperature varies for different types and materials of thermocouples.

2. Calculation formula for excessive temperature of standard thermocouples
For standard thermocouples, the formula for calculating excessive temperature is as follows:

Δ T=(T1-T0)/(K × α)

Among them, Δ T represents excessive temperature, T1 represents the working temperature of the thermocouple material, T0 represents the maximum temperature of the thermocouple, and K represents the sensitivity coefficient of the thermocouple, α Represents the temperature coefficient of the thermocouple material.

3. Example explanation
Taking K-type thermocouple as an example, if its operating temperature is 500 ° C, the maximum temperature is 900 ° C, and the sensitivity coefficient is 20 μ V/° C, with a temperature coefficient of 0.02%/° C, the calculation process for excessive temperature is as follows:

Δ T=(500-900)/(20 × 0.0002)=-2000 ° C

Through calculation, it is known that the excessive temperature of the standard thermocouple is -2000 ° C, indicating that the working temperature has exceeded the limit temperature range.

4. Factors affecting excessive temperature
In addition to considering the material parameters of thermocouples, there are also some other factors that can affect the calculation of excessive temperature:

The excessive temperature increases with the increase of temperature gradient.

The excessive temperature increases with the extension of measurement time.

The excessive temperature increases with the presence of an oxidizing atmosphere.

(4) The usage status of thermocouples: The excessive temperature increases with the aging degree of thermocouples.

5. Methods to prevent excessive temperature
To ensure the accuracy and stability of temperature measurement results, it is necessary to prevent the occurrence of excessive temperature:

(1) Choose the appropriate thermocouple model and material.

(2) Reasonably determine the range of use of thermocouples based on working conditions and requirements.

(3) Control the temperature gradient to avoid rapid or slow heating and cooling.

(4) Regularly inspect and maintain thermocouples, and replace severely aged thermocouples in a timely manner.

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The calculation of excessive temperature of standard thermocouples is an important step in ensuring the accuracy and stability of temperature measurement results. By selecting appropriate formulas and parameters correctly, and considering the working conditions of thermocouples from multiple aspects, it is possible to effectively prevent the occurrence of excessive temperature and improve the reliability of temperature measurement.