Oxygen Gas sensor BT59i

The Oxygen Gas sensor BT59i measures the gaseous oxygen concentration in the range of 0 to 100 %. It uses an electrochemical cell, which contains a lead anode. The anode and cathode are immersed in an electrolyte. When oxygen molecules enter the cell, they get electrochemically reduced at the cathode. This electrochemical reaction generates a current that is proportional to the partial pressure of oxygen in the gas mixture. The current is measured across a resistance to generate a small voltage output. The voltage output is amplified to the 0 .. 5V output range.
The Oxygen Gas sensor has a limited operating lifetime because the chemicals in the electrochemical cell are depleted over time. A lifetime of the sensor will depend on the way it is stored and exposed to open air.