The document explains the function and types of oxygen sensors used in vehicles, which are vital for regulating fuel supply and monitoring catalytic converter efficiency. It details the structure of the sensors, particularly the zirconia type, and how the voltage generated from the difference in oxygen concentration is used by the engine control unit (ECU) to adjust the air/fuel mixture. Overall, oxygen sensors are crucial for optimizing engine performance and reducing emissions.

1. BY- AAYUSHI NANDA
VIT UNIVERSITY, VELLORE

2. Oxygen sensor is located on the exhaust line
; one before catalytic converter (upstream
/precat sensor) and one after catalytic
converter( downstream/ postcat sensor).
Upstream sensor is used for regulating the
fuel supply.
While downstream sensor monitors the
efficiency of the catalytic converter.

3. High pressure and temperature exhaust gases
leaving the engine cylinder during the exhaust
stroke travel through the exhaust manifold
and come in contact with the O2 sensor placed
before the catalytic converter.
fig. oxygen sensor placed on the exhaust pipe

6. The oxygen sensor plays a critical role in
providing optimum engine performance with
minimal emissions.
There are three basic types of oxygen
sensors. They are the:
• Zirconia
•Titania
• Air Fuel

7. The sensing element at the front of the
sensor consists of a zirconium dioxide sensing
element enclosed within a steel shell.
The sensing element is further connected to
platinum electrodes and wire leads down the
line.

9. Exhaust gas consisting of oxygen molecules
contacts the sensing element after flowing
through the slots or holes on the steel shell.
Outside air is made to flow through the gaps
between the connecting cables . This air is then
heated to enable the ions to produce voltage.
The difference in concentration of the oxygen
molecules in the exhaust gas and the ambient air
drives the oxygen ions from higher conc. To
lower concentration.

10. Due to the movement of oxygen ions from one
platinum layer to the other, a potential
difference is generated.
A rich mixture surges the voltage up to 0.9V.
Lean mixture drops the voltage down to 0.1 V.
These voltage signals are then fed to the ECU.
The ECU then compares it with the pre stored
standard data to decide whether the mixture is
rich or lean. And these calculations manipulate
the air/fuel mixture during the subsequent
stroke.

12. Thankyou