This combined single-rod measuring chain (platinum and reference electrode in one shaft) has an annular gap diaphragm with polymerized solid electrolyte. This prevents deposits and blockages and achieves a fast response time. The additional salt reservoir improves the service life. The single-rod measuring chain was specially developed for use in chromate reduction, nitrite oxidation, swimming pool and drinking water disinfection in heavily contaminated media. It can be used for a redox range of plus/minus 1500 mV and has a temperature resistance of -5 to +90 °C. The installation length is 120 mm.