10 Electronic measuring devices for determining the concentration of a substance in an in-vitro or in-vivo specimen containing body or other liquids, comprising of a first electrode covered by a cover layer of insulating material, a signal source connected to the first electrode applying a modulated electrical voltage to the first electrode for generating an electric field in the specimen, a measuring circuit for measuring at least one parameter depending on a response of the specimen to the field, and a data processor determining the concentration from the parameter; electronic measuring devices and electronic measuring instruments, namely, electronic glucose sensors and electronic steering devices for insulin pumps