A sealed electrode assembly for fluid measurements in a pressurized pipe having a wall, for providing contact between an electrode in contact with the fluid and the outside. The assembly includes a conductive bolt extending from the electrode and through the wall, a lining in the pipe having an opening for the bolt and insulating the electrode from the wall, a sealing ring fitted around the bolt, a mantel surrounding the bolt having a recess partially accepting the sealing ring and provided a pressure on the sealing ring when pressed into the recess, and a tightening structure on the outside of the wall for applying a pressure forcing the electrode toward the wall and thus a pressure between the lining, sealing ring and mantel.