Precise, electrometric measurement of pH and other ion activities is greatly simplified for practical applications by means of a sophisticated physical and chemical solution with the entire measuring setup permanently stabilized. The electrolyte for the reference electrode and the activating solution for the measuring electrode are usually identical in this new rapid-measurement concept. This completely eliminates various measuring errors often neglected in practice as well as the frequent recalibration. Factory-adjusted pH, pC, and other px-meters with integrated sensors, usually in combination, have already worked well under difficult conditions, e.g. in maintenance of sewage detoxification plants, field measurements, and in new fields of application for electronic pH measurement.