SaM - Thermocouples (Class I & II)

Remeber:

Reduced Range of thermocouples: The reduced range is a range of temperatures more than the actual measurement range of the devices, in this range the error is “fixed”. Extended Range of thermocouples: While outside the reduced range, you have also to account for an additional error, which scales with temperature, so the more you are outsude the range, the more the total error will be.

Class I thermocouples:

• Reduced range: $[-40°\text{C}÷375°\text{C}]$, reduced range error: $\pm 1°\text{C}$.
• Extended range error: $0.004°{\text{C}}^{-1}$
  So the total error, in the extended range, would be: $1+0.004\cdot T$.

Class II thermocouples:

• Reduced range: $[0°\text{C}÷333°\text{C}]$, reduced range error: $\pm 2.5°\text{C}$.
• Extended range error: $0.0075°{\text{C}}^{-1}$

If we wish to represent a thermocouple here’s the equivalent electric circuit, really simple:

• $R_S$ is the resistance given by the thermocouple.
• $\sim 40\frac{\mu \text{V}}{°\text{C}}$ represent a common sensitivity for a thermocouple.IMPORTANTE

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Memory Card

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And I remember you that the thermocouple obeying to the standard, which is IEC5842 of 1982, for class 1 devices, we have errors that can be of this entity here:

• THe reduced range is a range of temperatures more than the actual measurement range of the devices, class I is $[-40÷375°C]$, in this range we can have errors around $1°C$
• Whereas outside, in the extended range, you have also to account for an additional error, which scales with temperature, so the more you are outsude the range, the more the additional error will be.

Whereas for class 2 devices, we have an error:

• Here we can also see an euivalent circuit for a thermocouple, really simple.