This heat loss through the glass keeps the internal bulb temperature steady so that the two sides of the vanes can develop a temperature difference.

Unlike wet bulb temperature, dry bulb temperature does not indicate the amount of moisture in the air.

Halogen lamps are usually much smaller than standard incandescents, because for successful operation a bulb temperature over 200 C is generally necessary.

Assuming constant pressure, sigma heat is solely a function of the wet bulb temperature of the air.

In contrast, the dry bulb temperature can vary even for processes where there is no such net energy change.

In keeping with this, the wet bulb temperature also remains unchanged, as its reading already represented the maximum possible amount of evaporative cooling.

The dry bulb temperature however is in conflict with the sigma heat since it decreases during such evaporative cooling.

This is why measurements of sigma heat which use dry bulb temperatures must also take into account the humidity of the air.

Use a psychrometric chart to calculate wet bulb temperature, and then add 6-8 F as described above.

The dew point temperature is equal to the fully saturated dry bulb or wet bulb temperatures.