Retainer arrangement and method for applying a membrane to a physiological sensing unit

Disclosed herein are a method and a retainer arrangement 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 invention proposes the preparation of a preassembly thus constituting a spare part which will be ready for application to the sensing unit when needed. The preassembly comprises a membrane, a clamping ring for removably assembling the membrane with the sensing unit, and means, including an auxiliary retainer element, for temporarily and removably securing the membrane to the clamping ring prior to assembly with the sensing unit.