Abstract: In an apparatus for detecting the surface of a liquid or foam, for example in a fermentation vessel a detector electrode (10) is surrounded at its lower end by a protective shroud (12) so as to protect a confined vapor space (14) surrounding the detector electrode. The vapor in the space (14) is maintained at a relatively low humidity either by heating the detector electrode or some other part of the apparatus or by purging the space (14) with a relatively dry air or gas. It is thereby ensured that no condensation onto the O-ring seal (20) and surrounding parts takes place. The shroud (12) also protects the parts from splashing.

Abstract: A system is disclosed for measuring the oxygen concentration in a fluid contained in a fermentation vessel, comprising a fermentation vessel containing a nozzle aperture disposed in the wall thereof, an electrode holder slidably disposed within the nozzle aperture, the electrode holder being provided at one end thereof with an oxygen permeable membrane which provides a wall across the aperture in the vessel for contact with the fluid to be examined, a diaphragm oxygen electrode mounted in the electrode holder of the fermentation vessel so that the diaphragm of the electrode and the oxygen permeable membrane are in close contact with each other, whereby the oxygen concentration of the fluid contained in the fermentation vessel is measured. A method for measuring the oxygen concentration in a fluid contained in a fermentation vessel is also disclosed.

Abstract: A carbon dioxide sensor for measuring dissolved carbon dioxide or carbon dioxide in gas is sterilizable with steam under pressure at a temperature of 120-130 degrees Celsius. The sensor comprises an outer tube having on its one end a gas-permeable membrane and a pH electrode disposed in the outer tube and supporting a spacer of poor hydrophobicity positioned between the distal end of the electrode and the membrane. For measurement of carbon dioxide, a liquid containing sodium bicarbonate is poured into the outer tube to form a layer of electrolyte at the spacer, and the outer tube is mounted on a fermentor. The pH electrode can be removed from the outer tube which is attached to the fermentor, and a membrane protecting rod can be inserted into the outer tube for sterilization of the membrane. The gas-permeable membrane can easily be replaced.

Abstract: A carbon dioxide sensor for measuring dissolved carbon dioxide or carbon dioxide in gas is sterilizable with steam under pressure at a temperature of 120-130 degrees Celsius. The sensor comprises an outer tube having on its one end a gas-permeable membrane and a pH electrode disposed in the outer tube and supporting a spacer of poor hydrophobicity so as to be positioned between the distal end of the electrode and the membrane. For measurement of carbon dioxide, a liquid containing sodium bicarbonate is poured into the outer tube to form a layer of electrolyte at the spacer, and the outer tube is mounted on a fermentor. The pH electrode can be removed from the outer tube which is attached to the fermentor, and a membrane protecting rod can be inserted into the outer tube for sterilization of the membrane. The gas-permeable membrane can easily be replaced.