Bosch L-Jetronic Electronic Fuel Injection

Fig. 5 Oxygen sensor.:

The outer part of the oxygen sensor is constructed of ceramic and is exposed to the exhaust gas flow, Fig. 5. The inner part of the sensor is exposed to ambient air temperature. If the oxygen content is different on both sides of the sensor, a voltage is created across the two outer surfaces of the sensor. This voltage allows measurement of the difference in oxygen content on each side of the sensor.