Re-Usable-Sensor (RUS) in Single-Use PolarWell
Mettler Toledo manufactured for many years the MT InPro 6800 family of polarographic oxygen sensor. CerCell manufacture and install optionally (before bagging and E-beam irradiation) the non-invasive transparent Polycarbonate tube / Silicon membrane product named PolarWell.
In real life the user inserts their own DO Re-Usable-Sensor (RUS) into the non-invasive PolarWell Single-Use-Well (SUW). And fasten gently, tighten slightly by hand until 0.5 Nm torque. There is no direct contact between the MT InPro 6800 (pn 52 201 013) and the media, broth. No autoclaving of InPro is required insuring the sensor obtain a long and stable lifetime. PolarWell for the InPro is available in PG 13.5 x 120, 220, 320, 420 sizes.
The polarographic sensor principle is invented by Prof Leland Clark early 1960ties. The sensor electrode tip is isolated from the broth by a thin Silicone (originally Teflon) membrane. The membrane is permeable to molecular oxygen and allows this gas to reach the cathode, where it is electrolytically reduced. The reaction is diffusion limited and depends strongly on the permeability properties of the membrane and by the oxygen gas concentration, which is the measured quantity.