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AF sensor vs O2 sensor | Difference between Air Fuel ratio sensor,O2 sensor

This page compares AF(Air Fuel) sensor vs O2 (Oxygen) sensor and mentions difference between AF ratio sensor (Air Fuel ratio sensor) and O2(Oxygen) sensor.It mentions working of oxygen sensor and internal construction of Air Fuel ratio sensor and O2 sensor.

We will understand O2 sensor and AF sensor used in automobile industry in vehicles to control air fuel mixture. O2 stands for Oxygen and AF stands for Air Fuel and hence their short name derived from this. As AF sensor is modification of original oxegen sensor, it is known as wideband oxygen sensor.

Oxygen sensor, O2 sensor working

The figure-1 depicts working of oxygen sensor. O2 sensor works in closed loop operation. As shown in the figure, ECU (Engine Control Unit) takes input from various different sensors such as throttle position sensor, MAF sensor, MAP sensor and air temperature sensor and gives out A/F ratio (i.e. Air to Fuel ratio). This air fuel is present in the exhaust pipe of the engine where O2 sensor is located.

Ideally air fuel ratio should be 14.7 in number. Oxygen sensor gets information of the air fuel ratio and based on this it will direct ECU to reduce or increase the injection of the fuel in order to maintain the ratio.

O2 Sensor | Oxygen Sensor

O2 sensor or Oxygen Sensor

The figure-2 depicts internal construction of the O2 sensor. As show oxygen sensor is constructed with two platinum electrodes and zirconium dioxide element between the electrodes.

As exhaust displaces the oxegen in the oxygen pipe. The platinum electrodes react to the potential difference in oxygen content between outside air and inside of exhaust pipe. This potential difference creates electrical current (i.e. voltage).

Typically O2 sensor generates 0.2 to 0.7 volts at 600 degree fahrenheit. For the correct mixture, O2 sensor produces 0.5 Volt. It will produce over 0.5V for reach mixture and will produce below 0.5V for lean mixture.

AF Sensor | Air Fuel Ratio Sensor | Air Fuel Sensor

A/F or Air Fuel Ratio Sensor

The figure-3 depicts internal construction of the Air Fuel ratio sensor. This sensor is based on operation of original oxygen sensor. It consists of two O2 sensors housed in one common area with common chamber between them. This wideband Air Fuel sensor adds two chambers to the original zirconium sensor named diffusion chamber amd air reference chamber.

Conclusion: O2 Sensor measures oxygen through voltage. Air Fuel ratio sensor uses current to measure air to fuel ratio. AF sensor uses minimal current for its operation. This is the difference between Air fuel ratio sensor and O2 sensor other than the inner construction.

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