Abstract: A disk-shaped thin plate or a long-sized thin plate having a roll appearance housed in a casing in which openings for penetration of test substance are formed and on which diffusion-limiting membranes are adhered to cover each openings. Also a driving mechanism for moving the thin plate is provided with the casing. The casing thus houses the thin plate and is provided with the driving mechanism and is positioned in a test apparatus body having a concentration measuring electrode therein. Multiple measurments of concentration of a test substance are carried out by moving the thin plate by the driving mechanism to position the diffusion-limiting membrane having the test solution deposited thereon to the position available to contact with the concentration measuring electrode, while keeping the casing placed in the test apparatus body. As a result, a plurality of measurements of concentration of the test substance is carried out easily.

Abstract: An apparatus for mounting a diffusion-limiting membrane for a sensor in which a mounting member for mounting a diffusion-limiting membrane holding plate is movable toward and away from an enzyme electrode unit and in which, with the mounting member positioned away from the enzyme electrode unit, a diffusion-limiting membrane holding plate having a diffusion-limiting membrane mounted thereon is mounted on or removed from the mounting member, thus preventing the diffusion-limiting membrane from being slidingly rubbed with the surface of the enzyme electrode and in which, with the holding plate mounted on the mounting member, the mounting member ius moved toward the enzyme electrode unit, causing the diffusion-limiting membrane to be stuck to the surface of the enzyme electrode unit.

Abstract: A diffusion-limiting membrane holding means for a sensor comprising: a slender resilient thin plate, of which one shorter side serves as an engagement side, and of which one longer side is provided at its predetermined position with an engagement portion, an opening being formed in the thin plate between the engagement side and the engagement portion; and a diffusion-limiting membrane integrally attached to the thin plate as covering the opening; whereby the resliency of the thin plate causes the diffusion-limiting membrane to be stuck to the surface of an enzyme electrode unit of a sensor, thus enhancing the accuracy of concentration measurement of a target substance to be measured.