Abstract: Disclosed herein is a retainer assembly for applying a membrane to a physiological sensing unit for the transcutaneous determination of the magnitude of physiological quantities, particularly for measuring the partial pressure of gases in blood or the like. The assembly constitutes a preassembly of a membrane, with a clamping ring accommodating the membrane and having an annular recess receiving the rim of the membrane. The clamping ring has a lip in the form of an inwardly protruding annular edge for removably securing the clamping ring together with the membrane to the sensing unit by virtue of the lip resiliently snapping into a peripheral groove of the sensing unit, the lip defining the periphery of the annular recess. A retainer element is provided for temporarily and removably assembling the membrane with the clamping ring prior to assembly with the sensing unit.

Abstract: A measuring sensor head for determining the contents of gases in liquids, particularly for transcutaneous determination of oxygen in blood, as well as a method of manufacturing such sensor head are disclosed. In accordance with the invention, the gas-permeable membrane which covers the front face of the sensor head and which, during use, is applied to the human skin, is preshaped to assume a cap-shaped configuration. This eliminates previously occurring measuring errors due to uncontrollable stresses causing thickness variations generated in conventional membranes and, moreover, provides for an improved sealing effect between the housing of the measuring head and the membrane.