Abstract
This chapter tells how to measure plant water potential using thermocouple psychrometers. The theory of their use is given. It includes knowing the relation between water potential and relative humidity (called the Kelvin equation); the Peltier thermoelectric effect; Joule heating; thermoelectric power; and the relationship between vapor pressure and temperature (called the psychrometric equation). Each of these topics is discussed. A sample problem is given showing how to get partial pressure of water vapor in air, relative humidity, vapor pressure deficit, and dewpoint temperature from wet and dry bulb readings obtained from a psychrometer. Calibration of thermocouple psychrometers and how one takes measurements with them are described. The importance of isothermal conditions during measurements is emphasized, and reasons for them are enumerated. Four types of thermocouple psychrometers are distinguished: the isopiestic thermocouple psychrometer; the Spanner thermocouple psychrometer; the Richards-and-Ogata thermocouple psychrometer; and the dewpoint hygrometer. Appendices give biographies of Peltier, Joule, and Kelvin.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
