DEWPOINT
DEWPOINT [ F, C, R, K] returns the dewpoint temperature for air-water gas mixtures. The value and units of the returned value depends on the Unit System setting. This function can be used only with AirH2O as the substance name. Three arguments follow the substance name in any order: temperature (T), total pressure (P), and relative humidity (R) or humidity ratio (W) or wetbulb temperature (B).
The letters in parentheses are the identifiers for each property. A complete list of the identifiers and instructions are available in the Thermophysical Function help.