The fundamental principle of conductivity instrument

 The fundamental principle of conductivity instrument

一：the conductivity test and the basic principle of eddy current testing are basically the same,are according to the theory of electromagnetic field of electromagnetic induction phenomenon ,namely take advantage of testing coil with alternating current is close to the conductive specimen, the surrounding alternating magnetic field can make the specimen induce eddy current (eddy current ),the size of the vortex flow ,phase and flowing form are  influenced by factors such as the performance parameters of the specimens, and the magnetic field generated by the eddy current and makes the test coil impedance changed , so it can be concluded that the conductivity difference of test specimen by testing the change of test coil impedance .

二:the physical significance of the conductivity, according to its electrical conductivity, the material can be divided into :insulators,semiconductors,conductors,superconductor (the conductor under the special condition )

Metal materials can be conductive because in the metal,the outermost electron of atoms is weak to bound to a nucleus,they can free of nucleus at normal temperature and become a free electrons ,freedom of movement within the metal,normally,in an instant crossing section of conductor,the power can be offset each other,namely there is no current flow through the conductor,if provide potential difference on both ends of a conductor,namely the conductor produces electric field,the free electrons in the electric field will move to high electric potential from low potential ,there are a lot of free electrons in conductor,it is easy to happen electron flow,so the conductor will easily be conductive,in this case,any section of conductor will have certain electric current flows through。

Because of the free electrons in the metal material will impact on atoms or other free electrons in the process of movement ,free electrons motion speed will slow