NOx sensor for Truck | Kreation

NOx sensor consists of a ceramic sensor element and an electronic control unit.

The smart NOx sensor measures the NOx concentration, air/fuel ratio (A/F ratio) and equilibrum oxygen partial pressure in the exhaust gas of combustion engines and can be used for

· Lean burn engines (NOx trap)

· engines (SCR catalysts, NOx trap, closed-loop NOx control)

· On board diagnostics, OBD 

A ceramic sensor made of zirconia electrolyte measures in amperometric operation the oxygen concentration entering from exhaust gas through a diffusion barrier into a first cavity. The oxygen concentration inside the cavity is controlled to the constant concentration of a few ppm NOx. Other components of the exhaust gas also entering the cavity as HC, CO and H2 are oxidized at the pumping electrode made of Pt.

From the first cavity the test gas with a few ppm O2 and NOx enters a second cavity, where gaseous oxygen is totally removed by an auxiliary pump. At the measuring electrode the equilibrium of NO <-> N2 + O2 is changed by removing oxygen generated by the reduction of NO. The amperometric measurement IP2 of this generated oxygen represents the NOx concentration of the exhaust gas.

An sensor control unit (SCU) provides the power control for heating the sensor element to operating temperature. In an ASIC the regulation for the amperometric operation of all pumping cells to determinate NOx concentration, air/fuel ratio and binary l signal is realized. The SCU provides the measured gas concentrations digitally via CAN bus.

The assembly of the entire NOx sensor system, consisting of sensor and electronic control unit connected by a wiring harness is shown in next drawing.