Measuring electrode

A measuring head assembly for making pH measurements such as for transcutaneously determining CO.sub.2 partial pressure, the measuring head assembly comprising:

• a measuring head defining a measuring head surface and having an opening formed in said surface;
• a reference electrode having a first measuring surface and being mounted in said opening so as to cause said first measuring surface to be next to said measuring head surface, said reference electrode further having a receiving opening formed therein;
• a measuring electrode unit mounted in said receiving opening, said unit including:
• a supporting structure made of electrically insulating material and defining a cavity electrically insulated from said reference electrode;
• an electrode lead seated in said supporting structure with a portion of said lead extending into said cavity;
• a solid contact body filling said cavity so as to embed said portion of said lead therein to establish electrical contact therewith;
• said solid contact body containing a mixture of a metal oxide, the metal of said oxide and a matrix carrier;
• and,
• said solid contact body having an outer surface defining a second measuring surface having a width greater than the diameter of said lead;
• said measuring head surface, said first measuring surface and said second measuring surface being disposed one next to the other and being mechanically shaped so as to be flush and conjointly define a smooth, uninterrupted composite measuring surface.