Dissolved oxygen measured by cell with membrane - clamped onto ring which surrounds cathode mounting

摘要

An appts. for measuring oxygen dissolved in a measuring liquid, esp. water, more partic. in the range of 15mg/l. comprises a measuring cell, a pref. Au cathode and a pref. Ag anode in the cell casing and electrolyte chamber contg. the electrolyte liquid. A membrane permeable to dissolved oxygen is stretched across the cathode and oxygen diffusing through the membrane is reduced at the cathode and thereby generates a diffusion boundary current. The membrane is fixed in liquid-tight manner around its perimeter to a cylindrical ring mounted in the housing; this ring contains (surrounds) a cylindrical component which itself contains the cathode and bears with its opposite face against the support surface of the housing. The arrangement permits easy changing of the membrane. Because the membrane is supported there is no risk of electrolyte loss during membrane changing. The membrane always has a defined mechanical stress.