At least one conductor is formed at a preselected location on a substrate made of a first insulating material having a high temperature resistance. The conductor is made from a solidified electrically conductive thick film material. A coating made of a second insulating material is formed over the substrate to hermetically seal at least a portion of the conductor. An exposed distal region of the conductor provides a detection electrode. The conductor has a reduced porosity that inhibits migration of fluid or constituents thereof through the conductor.
