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SIMPLE AUTOMATIC SCANNING AND RECORDING SYSTEM FOR THE MEASUREMENT OF WATER POTENTIALS WITH DROPLET THERMOCOUPLE PSYCHROMETERS
Author(s) -
BARRS H. D.
Publication year - 1969
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1969.tb06504.x
Subject(s) - thermocouple , hygrometer , galvanometer , chart , thermometer , environmental science , acoustics , meteorology , electrical engineering , optics , physics , mathematics , engineering , humidity , thermodynamics , statistics , laser
S ummary A simple, automatic scanning and recording system designed specifically to receive the output from up to twenty‐five droplet thermocouple psychrometers is described. Essential components are a solenoid‐operated, low‐level switch, a high grade preamplifier and a potentiometric chart recorder capable of remote operation. Chart traces show noise level is low even on a 10 μ V range. Provision is made to correct psychrometer readings for temperature effects due to heat of respiration. Statistical comparison of psychrometer calibrations obtained with this system and with manual switching into a reflecting galvanometer show the former system is at least as accurate as the latter. Parallel leaf water potential measurements made with the two systems agreed closely.