ISHS Acta Horticulturae 421: II International Symposium On Sensors in Horticulture
DETECTING SURFACE CONDENSATION ON TOMATO PLANTS IN GREENHOUSES |
| Authors: | Y.Q. Wei, B.J. Bailey, D. Wilkinson, A. Lockwood, B.C. Stenning |
| DOI: | 10.17660/ActaHortic.1998.421.4 |
| Abstract:
An impedance-type sensor to detect the condensation of water on the surface of tomatoes growing in a greenhouse has been designed, built and tested. It was made from 0.08 mm thick, flexible copper-coated polyamide film. Interlaced comb-type electrodes with a separation of 0.25mm, were created using a photographic and etching process. Flexibility of the film enabled the sensors to make good thermal contact with the surface of tomato fruits. The performance of sensors with bare electrodes was compared with sensors coated with acrylic latex and vinyl acetate based latex, in different concentrations. Uncoated sensors gave good and repeatable responses whereas the coated ones had non-reproducible responses and overestimated the wetness period. This was attributed to the slow release of moisture absorbed in the latex. The uncoated sensors were used in a series of experiments to monitor condensation on tomato fruits. The experimental results showed that the total wetness periods, indicated by the impedance changes of the sensors, agreed well with those deduced from measurements of fruit surface and air dew point temperatures. | |
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