Enhancement of a Commercial Pressure Plate Apparatus for Soil Water Retention Curves

Pressure plates are widely used to measure soil water retention properties of soils in the laboratory with axis-translation technique. Imperfect sealing of the pressure chamber, exchange of water vapour between the soil and the air in the chamber, lack of soil-plate contact, part of the porous plate directly in contact with air in the pressure chamber, and evaporation of water from the ballast tube may lead to incorrect estimation of the water volumes exchanged by the soil. An improved version of a commercial pressure plate apparatus is presented, which proved able to reduce the intrinsic drawbacks of the original design. The system was also equipped with an image-processing based data acquisition system for continuous measurement of exchanged water.