The object of the Electrical Density Gauge (EDG) invention is to provide a low cost, portable, non-nuclear, and rugged field-use device that measures dry density in soils that have been constructed for use as road-beds and building foundations. This data is used to ensure the quality control of the constructed...http://www.google.de/patents/US6963205?utm_source=gb-gplus-sharePatent US6963205 - Electrically measuring soil dry density
