The instrument according to the insulated wire in the electric field distribution characteristics, represented by the distribution of electric field lines to reflect inner and outer conductor of electric field condition and the electric potential, potential difference, and other potential surface.Product is composed of a base, an outer insulating bracket, outer conductor connection piece, the metal ball, spherical external insulation thread, an inner insulating bracket, an internal conductor lugs, metal ball, ball insulation thread and the outer ball insulated wire composition.