Thermocouple psychrometry
Thermocouple psychrometry is a technique that infers the water potential of the liquid phase of a sample from measurements within the vapor phase that is in equilibrium with the sample. The theoretical relation between water potential of the liquid phase and relative humidity of the vapor phase is given by the Kelvin equation
Ψ = energy/volume = (RT/Vw) ln(p/po) [3.2.3–1]
where ψ is water potential (sum of matric and osmotic potential, MPa), R is the universal gas constant (8.314 × 10-6 MJ mol-1 K-1), T is temperature (K), Vw is molar volume of water (1.8 × 10-5 m3 mol-1), and p/po is relative humidity expressed as a fraction where p is actual vapor pressure of air in equilibrium with the liquid phase (MPa) and po is saturation vapor pressure (MPa) at T.
Citation Information
Publication Year | 2002 |
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Title | Thermocouple psychrometry |
DOI | 10.2136/sssabookser5.4.c22 |
Authors | Brian J. Andraski, Bridget R. Scanlon |
Publication Type | Book Chapter |
Publication Subtype | Book Chapter |
Series Title | Soil Science Society of America Book Series |
Series Number | 5.4 |
Index ID | 70194882 |
Record Source | USGS Publications Warehouse |
USGS Organization | Nevada Water Science Center; Toxic Substances Hydrology Program |