This is an Oxygen Cell / O2 sensor interfacing circuit. Oxygen sensor generates 2mV to 28mV by electro-chemical reaction of Pb and oxygen in contact with oxygen cell electrode. High concentration of oxygen gives high voltages. At 100% oxygen, O2 cell generate maximum voltage.
OOM102-1 is oxygen cell this sensor generate 14mV maximum in it initial life span. R1 is load resistor for O2 sensor. R2 and R3 are controlling the gain of AD820AS. AD820 is operating at 5V single supply. Further more ADS1013 ADC also operates on single 5V supply. Oxygen cell output is single polarity, so U2 does not need dual power supply. C1,C2 and R4 are filtering circuit for sensor output. Micro controller communicate with ADS1013 ADC with I2C protocol.
Oxygen Sensor Calibration
At 100% oxygen, O2 cell generate maximum voltage. This maximum voltage can be achieve by applying pure oxygen. Then secondly measure voltage at ambient air. ambient air oxygen is 21%. So these two points are calibration or reference points for system.
Oxygen cell widely use in medical ventilators, anesthesia , incubators and where need to control air and oxygen ratio.
Note: Oxygen Cell have limited life span just like any other battery or cell. So system should be capable of monitor cell performance and physically changeable easily from equipment.