Device for measurement of the potential with respect to the soil of a cathodically protected metallic structure

A measuring device for measuring the potential, relative to the earth, of a metallic structure at least partially buried in said earth and cathodically protected by an externally applied DC voltage, comprising in combination:

• a metallic, rod-shaped probe, having one end provided with an essentially conical tip for being driven into said earth, and having a major portion of the surface of said probe coated with an electrically insulating material, and a minor portion of said surface, near said one end, not coated with said insulating material, said uncoated portion constituting a measuring electrode;
• a dry reference electrode consisting of (a) a material selected from the group consisting of zinc-plaster of Paris and (b) plaster of Paris/copper sulfateplaster of Paris, situated in a transverse bore in the rod-shaped probe near one end, and electrically insulated from said probe;
• said measuring device having means for electrically connecting said measuring electrode to said metallic structure, and means for electrically connecting said measuring electrode and said reference electrode to a measuring circuit for measuring the potential difference between said measuring and reference electrodes.