Replaceable measuring electrode system

A rotatable shaft of a measuring electrode assembly, the shaft having an upper end adapted to be supported for engagement with a drive means and a free lower end adapted for supporting at least one electrode that is immersed for rotation in an electrolytic fluid for amperometric determination of chemical components in the fluid, said shaft comprising:

• at least one bore axially opening in an end face of the shaft lower end;
• at least one contact pin slidably received in said at least one bore and electrically isolated from the shaft;
• biasing means provided to act between the shaft and the contact pin in order to axially bias the contact pin towards the mouth of the bore;
• fastening means for removably attaching a measuring body to the shaft such that an electrode, when supported on said measuring body, electrically connects said contact pin under a resilient pressure exerted from the biasing means.