11 - Peltier psychrometers The Peltier cooling effect is applied to a small thermocouple until condensation takes place. When the electric circuit is opened, evaporation starts and the thermocouple junction will act as a wet-bulb thermometer. The generated electomotive force is proportional to the wetbulb depression and allows the determination of the water vapor pressure. This type of instruments are used for accurate measurement of water potential in plant tissues and soil samples. 2.3. Sunshine and Radiation 2.3.1 General comments 2.3.11 Physical aspects Radiation fluxes to and from the earth's surface are most important meteorological elements for heat and energy balance assessments. As the energy conversion from solar radiation mainly takes place on the surface of the soil and of plants.
