reference electrode the at least partial shielding of the reference electrode against substances that would lead to a change in the reference potential when reaching the reference electrode is arranged in the vicinity of the reference electrode a highly stable reference potential can be obtained with the present invention application_number US 26918405 A description referring to the drawings in particular the embodiment of fig1 is a three electrode electrochemical sensor according to the present invention comprising a housing 1 in which an opening is closed by a membrane 2 which is open for diffusion and behind which a measuring electrode 3 is located a reference electrode which is designed as a u201c swiss roll u201d structure is arranged in the central area of the electrolyte space 4 the reference electrode containing at least one layer of a material of a reference electrode 5 and a layer of a material of a protective electrode 6 the two materials being rolled around each other and the material of the protective electrode 6 closing off the overall arrangement to the outside and toward the electrolyte space 4 a counterelectrode or auxiliary electrode 7 is arranged on the side of the sensor housing 1 facing away from the measuring electrode 3 layers of nonwoven material 8 are arranged between the layers of the material of the reference electrode 5 and the layers of the material of the protective electrode 6 so that an intimate contact is guaranteed between the electrolyte and the electrode material in the immediate vicinity of the reference.