NOx sensors used in the automotive industry are primarily of the amperometric type and feature two to three electrochemical cells in separate chambers.
The first cell removes O2 from the sample to prevent interference with the NOx measurement in the second cell.
These sensors are commercially available from multiple suppliers and are used to control NOx adsorber and SCR aftertreatment systems. Additionally, NH3 sensors have been developed for use in SCR systems.
The development of these sensors began in the 1990s and commercial versions were first introduced in the early 2000s for use in lean-burn gasoline passenger cars and diesel vehicles with NOx adsorbers and urea-SCR aftertreatment for light and heavy-duty diesel engines.
The NOx sensor measures the amount of nitrogen oxides (NOx) present in the exhaust gas of an internal combustion engine. These sensors use an electrochemical cell to detect the concentration of NOx in the exhaust stream and provide real-time feedback to the engine control system, which can then adjust the air-fuel mixture or the operation of the NOx aftertreatment system to reduce emissions. The sensor’s function is crucial in ensuring that the engine meets emission standards and operates efficiently.