In thermocouple when, keeping the temperature of the cold junction constant, the temperature of the hot junction is gradually increased.

The thermodynamic emf rises to a maximum at a temperature (θ_n) called neutral temperature and then gradually decreases and eventually becomes zero at a particular temperature (θ_i) called temperature of inversion.

If, the inversion temperature and neutral temperature both measured in degree Celsius, then we can say "inversion temperature is always double the neutral temperature"

But if measured in other units such as Kelvin, inversion temperature may not be double the neutral temperature