Zirconium dioxide lambda sensor

Zirconium dioxide lambda sensors are used as a regulating and as a diagnostic sensor, depending on the vehicle.
Zirconium dioxide lambda sensor

This lambda sensor is comprised of a zirconium-dioxide-based solid electrolyte. This material is conductive for oxygen ions at temperatures of 300 °C or higher.

Through electrodes which are attached on the interior side (reference / environmental air) and on the element the exhaust side (sample gas), the oxygen content of the exhaust gas can be measured.

The output signal is generated by oxygen ions, which pass through the element and attempt to compensate for the oxygen difference (oxygen partial pressure differential).

The zirconium dioxide lambda sensor is distinguished by the following characteristics:

  • Fast operational readiness
  • Temperature resistance
  • Not sensitive to hydraulic shock
  • Resistant to contamination
  • High level of reliability

These sensors are used as a regulating and as a diagnostic sensor, depending on the vehicle.

The zirconium dioxide sensor element is finger-shaped and hollow. The interior has contact with the ambient air. The outside lies in the exhaust flow. Both sides are covered in a thin porous layer of platinum acting as an electrode.
Principle of the zirconium dioxide sensor

Method of operation of the zirconium dioxide lambda sensor

The zirconium dioxide sensor element is finger-shaped and hollow. The interior has contact with the ambient air. The outside lies in the exhaust flow. Both sides are covered in a thin porous layer of platinum acting as an electrode.

If the lambda sensor reaches operating temperature, the oxygen ions flow on the basis of the varying oxygen concentration. Oxygen ions from the outside air also move in the direction of the exhaust in order to equalise them.

The voltage is proportional to the oxygen concentration

The resulting potential differential gives rise to an electrical voltage (U) at the platinum electrodes. If the mixture is lean the sensor signal is approx. 0.1 volts. If the mixture is rich, it is 0.9 volts. If lambda=1 a characteristic voltage jump of 0.8 takes place.

Cable assignment

Zirconium dioxide sensors from NTK can have up to four cables.

Unheated sensors with earth contact through the thread come with a black signal cable. Unheated sensors with their own earth contact for the vehicle have an additional, grey earth cable.

Heated sensors have either three or four cables. Here the black cable always carries the sensor signal. Two white cables are responsible for the current supply of the heater. If the earth connection does not take place through the thread, there is an additional grey earth line to the vehicle electrical system.

Cable assignment for heated and unheated zirconium dioxide sensors