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An Electronic Sensor for Vapor‐Pressure Deficit of the Air 1
Author(s) -
Johnson W. C.,
Davis R. G.
Publication year - 1978
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1978.00021962007000050042x
Subject(s) - thermistor , diode , hygrometer , evapotranspiration , vapour pressure deficit , voltage , multiplier (economics) , limiting , electrical engineering , materials science , environmental science , optoelectronics , humidity , chemistry , engineering , meteorology , physics , mechanical engineering , ecology , biochemistry , photosynthesis , transpiration , macroeconomics , economics , biology
The parameter of vapor‐pressure deficit (VPD) is used in several methods of calculating potential evapotranspiration. This note describes an electronic sensor for measuring VPD whose principle of operation is based on wet and dry‐bulb psychrometry and utilizes thermistors and silicon diodes as wet and dry‐bulb probes. These probes produce two voltages which, when multipled together by an inexpensive, commercially available, analog multiplier, result in an output voltage proportional to VPD that can be recorded continuously on a strip chart recorder. The VPD sensor has shown good reliability in actual field tests with accuracy that would not be a limiting factor in calculating potential evapotranspiration. Detailed information on construction and operation of the sensor is available from the authors and will be mailed on request.