Leaf wetness is a meteorological parameter that describes the amount of
dew and precipitation left on vegetation. It is used for monitoring leaf moisture for
agriculture purposes, such as
fungus and
disease control, for control of
irrigation systems, and for detection of
fog and
dew conditions, and early detection of
rainfall.
[ The Leaf Surface Wetness Duration Home Page, Cornell University]
Leaf wetness may be measured by various means:[ Types of sensors, The Leaf Surface Wetness Duration Home Page][ Some leaf wetness sensors, Campbell Scientific]
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By change in electrical resistance between two metal conductors in an alternate finger
[ Resistance type sensor , Davis Instruments] or double spiral[ Double spiral configuration , ICT International] configuration on a flat surface, either flat or cylindrical.[ A comparison of cylindrical and flat plate sensors for surface wetness duration: Gillespie T.J., Duan R.X., 1987. Agric For Meteorol 40: 61-70.] The conductors are usually gold plated for corrosion resistance. An issue with this method is that measurements depend on droplets being large enough to bridge the gap between the conductors. A surface coating of for instance hygroscopic latex paint may be applied for more consistent results.[ Do you measure leaf wetness?, Decagon Devices][ Effects of coating, deployment angle, and compass orientation on performance of electronic wetness sensors during dew periods: Lau, Y.F., Gleason, M.L., Zriba, N., Taylor, S.E., Hinz, P.N., 2000. Plant Disease 84:192-197.][ Electronic leaf wetness duration sensor: why it should be painted: Sentelhas, P.C., Monteiro, J.E., Gillespie, T.J., 2004. Int J Biometeorol 48: 202-205.] Resistance measurement is often by alternating current excitation.[ Leaf Wetness Sensor , LWET]
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By measuring the change in the dielectric constant of the surface of a sensor, thus detecting the presence of water or ice on the sensor's surface.
[ Dielectric Leaf Wetness Sensor , Campbell Scientific]
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A sensor with hygroscopic properties where a change in sensor length or weight can be measured mechanically.
See also
