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Development and Testing of a Low-Cost Condensation Detection System

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  024013,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.9176) @2002
Authors:   Braun, M.J., Montross, M.D., Beaman, C., Duncan, G.A., Gates, R.S.
Keywords:   Greenhouse, grain bin, moisture, ventilation.

A system was designed to detect condensation using a leaf wetness sensor. The leaf wetness sensor was a variable resistance device that was a function of moisture on the surface. A circuit was developed to compare the sensor output to a reference voltage and control a relay for ventilation. The system was validated in an environmental chamber in the laboratory using a heat exchanger and water bath. Condensation was immediately detected when the plate was cooled below the dew-point temperature of the chamber. When the water temperature increased above the dew-point temperature there was a delay as the moisture was evaporated from the plate. Dirt and other foreign material were added to the leaf wetness sensor with little effect on system performance. The dirt acted to delay the sensor from drying and predicted slightly longer condensation periods. The system was tested in a tobacco greenhouse and a grain bin and was verified using relative humidity sensors and thermistors. There were frequent periods of condensation in the greenhouse and the system accurately predicted them. Condensation did not occur in the grain bin as a result of the dry conditions the grain was stored under. The relative humidity and thermistors verified that condensation probably did not occur during storage.

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