Question

The temperature of inversion of a thermocouple is $620^{\circ }C$ and the neutral temperature is $300^{\circ }C$, what is the temperature of cold junction?

• A. $20^{\circ }C$
• B. $320^{\circ }C$
• C. $-20^{\circ }C$
• D. $40^{\circ }C$

Answer 1

Answer: (C)

The temperature of inversion is higher than the neutral temperature by the same amount as the neutral temperature is higher than the temperature of cold junction.
As per Key Idea
$t_n-t_0=t_i-t_n$
$\Rightarrow t_0=2t_n-t_i$
Given, $t_i=620^{\circ }C,t_n=300^{\circ }C$
Hence, $t_0=$ temperature of cold junction
$=2\times 300-620$
$=600-620=-20^{\circ }C$
NOTE: Neutral temperature does not change for a metal whether the temperature of cold junction and inversion temperature change by any value.