S 420 (140.043) V8-4.2L (119.981) (1996)
The active sensor ceramic consists of a gas-permeable ceramic body manufactured from zirconium dioxide. A protective tube with several slots protects
the ceramic body from mechanical stresses and from temperature jumps.
The eletrical connection is performed by means of a 4-pin connector.
The capacity of the sensor heater at operating temperature is:
- 18 W (engines with ME 1.0, 2.0, 2,1)
- 7 W (engine 112, 113 with ME 2.8, engine 137).
O2 Sensors, Function
O2 Sensors, Function
1
Sensor ceramic
2
Electrodes at boundary surfaces
3
Exhaust pipe
Arrows
black: exhaust gases
white: outside air
The sensor ceramic is conductive for oxygen ions from approx. 300 °C. If the oxygen share varies greatly on both sides of the ceramic probe body, a
voltage (Nernst concentration cell) is generated on the friction planes by means of the particular properties of the ceramic probe body on the friction
plane. This is a measure for the residual oxygen content in the exhaust.
Curve of O2 sensor voltage, schematic
A
minimum sensor voltage (lean mixture)
B
maximum sensor voltage (rich mixture)