Consider a temperature probe used to measure a gas temperature. In the presence of significant radiation heat transfer, the equilibrium temperature probe may be different from the fluid temperature begin measured . Because radiation heat transfer is proportional to the fourh power of temperature, the importance of ration effects increases as the absolute temperature of the measuring environment increases. The error due to radiation can be estimated by considering steady-state thermodynamic equilibrium condition for a temperature seneor. Consider by case wher energy is transfer to / from a sensor by convection from the environment snd from/to the sensor by radiation neglected. A first law analysis of a system containing the probe, at steady-state conditions, yields