Campbell Scientific's KH20 krypton hygrometer is for measuring water vapor fluctuations in the air. it is typcially used the CSAT3 3-D sonic anemometer for measuring latent heat flux (LE), using Eddy Covaraiance technique. The sensor uses a krypton lamp that emits two absorpotion lines: major line at 123.58nm and minor line at 116.49nm. Both of these lines are absorbed by water vapor, and a small amount of the minor line is absorbed by oxygen. This device is intended for short, attended studies only and is typically used with fine wire thermocouples. It is designed for measurement of rapid fluctuations in atmospheric water vapor. It does not measure absolute concentrations.