HOW AN OXYGEN SENSOR WORKS?

BY- AAYUSHI NANDA

VIT UNIVERSITY, VELLORE

LOCATION INSIDE THE AUTOMOBILE?? 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.

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

OXYGEN SENSOR- CROSS-SECTIONAL VIEW

FIGURE - A CROSS-SECTIONAL VIEW OF A TYPICAL ZIRCONIA OXYGEN SENSOR.

OXYGEN SENSOR OPERATION

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

OXYGEN SENSOR OPERATION 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.

OXYGEN SENSOR

WORKING (CONTD..) 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.

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.

FIGURE -THE OXYGEN SENSOR PROVIDES A QUICK RESPONSE AT THE STOICHIOMETRIC AIR-FUEL RATIO OF 14.7:1.

Thankyou