Measuring apparatuses, namely, electrical or electronic measuring transmitters for measuring a physical, chemical, or analytical parameters, namely, pressure, temperature, mass flow rate, volume flow rate, filling level of a fluid or bulk material in a container, pH, oxidation-reduction-potential, ion concentration, electrical conductivity, turbidity, humidity, content of dissolved gasses in a liquid, especially, content of dissolved oxygen, total organic carbon content in aqueous samples, total nitrogen content in an aqueous samples, specific gravity, viscosity; spectrometers; photometers; potentiometric sensors, namely, pH-electrodes or electrodes for measuring oxidation-reduction-potential; plug connectors with galvanic isolation and inductive coupling; threaded plug connector head; connector plug for an electrode, said plug connector comprising a memory module containing sensor data, calibration data, and electronic signatures; connector cables for galvanically isolated connection between sensors and analyzers or transmitters; data recording apparatuses, namely, memory modules; display devices, namely, LCD-displays, TFT-displays; solar cells; battery modules, namely, battery packs; apparatuses for automated maintenance and automated calibration of pH-electrodes; downloadable or recorded computer software for operation, bringing into service, testing, maintenance, or calibration of the above measuring apparatuses; all of the above goods only in the fields of industrial process measurement instrumentation, industrial process automation, laboratory measurement instrumentation, laboratory automation, manufacturing automation, building automation, environmental measurement instrumentation, medical technology, and traffic engineering, none of the above goods in the fields of office technology and office equipment, respectively