Abstract: A portable device and method for measuring enthalpy and humidity of humid air from a space or flow channel at temperatures from 80.degree. to 400.degree. F. is described. The device consists of a psychrometer for measuring wet-bulb temperature, a vacuum pump for inducing sample air flow through the unit, a water-heating system for accurate psychrometer readings, an electronic computer system for evaluation of enthalpy and humidity from corrected and averaged values of wet- and dry-bulb temperatures, and a monitor for displaying the values. The device is programmable by the user to modify evaluation methods as necessary.

Abstract: In a psychrometer for measuring the humidity of a gas flow, especially a gas flow having a temperature of above 100.degree. C., a flow of liquid is supplied to a wick surrounding the wet sensor via a preheater which heats the liquid to approximately the wet bulb temperature of the gas stream before the liquid comes into contact with the wet sensor, thereby avoiding cooling of the wet sensor by the liquid. The necessary preheating of the liquid can be achieved largely by heat exchange between the liquid and the gas flow downstream of the wet sensor; such heat exchange may be effected in part by using an auxiliary wick from which a portion of the liquid evaporates before the rest of the liquid reaches the main wick.