Hydrogen probe with limited active area

Claim 1

A hydrogen probe device comprising: an elongated tubular member formed of a hydrogen-permeable metallic material, said member having a first closed end formed of said hydrogen-permeable metallic material and a second open end for connection to a hydrogen-sensing device; an inner liner in said tubular member, said liner being formed of a hydrogen-impermeable material and extending a part of the length of said tubular member and being sealingly joined at each end to the interior of said tubular member whereby hydrogen permeating the portion of the length thereof between the sealed ends of said liner is prevented from entering the interior of said probe and passing out the open end thereof; and a vent means through the wall of said tubular member between the ends of said liner whereby hydrogen which permeates said tubular member between the sealed ends of said liner may pass freely from between the outer surface of said liner and the lined inner surface of said tubular member thereby preventing a buildup of pressure between the interior of the lined portion of said tubular member and the exterior of said liner, the extent of said vent means being from the exterior to the interior of said tubular member.