CHANG Banhong
(Machinary Dept)
Abstract: With the rapid detector to determine water contents in slip, we use a capacitance sensor mainly in the light of dielectric coefficience large in water and small in material itself. As water contents in material changes, it would cause a change in sensitive capacitane, In fact. the reason is not the change taken place in dielectric coefficient of material or wa ter, but it is the proportion between water and partial volume in material that causes changes.The capacitance formed by water and material can be expressed Cs= 0.0884(εsS/d) Band CL=0.0884(εLS/d) (1-B) respectively, B represents percentage of water contents' volume. uensitive capacitance actually consists of Cx= Cs+ C1. further analysis, we can find that sensitive capacitance of slip consists parallelly of fixed unchanging capacitance CLo (determined by dielectric coefficience of material) and changing capacitance with the changes of percentage B of water contents'volume in the material , that is: Cx=Cy+CLo,When Cy=0.0884 (εy S/d) B, percentage B of slip volume has linear relation with sensitive capacitance, which can be expressed with maths model B= bCy= bCx-bcLo.The experiment proves that analysis theory is in agreement with practical performance. This is a very important basis for designing capacitance sensor of rapid detector in slip water contents.
Keywords：capacitance sensor,capacitance,water contents