Automotive Air Quality Sensors
Using MiCS Air Quality Sensors
This application note describes the appropriate integration of a MiCS Air Quality Sensor in a modern automobile. MiCS is the AQS brand of e2v technologies.
Important note : Reproduction and distribution of this document is restricted by e2v. The following specifications are subject to change to accommodate continuous improvement.
The AQS function
The Air Quality Sensor is based on two semiconductor gas sensors that detect pollution peaks in the traffic. It calculates an “Air Quality level” that is sent to the CPU of the HVAC. The HVAC can then open and close the recirculation flap so as to minimize the pollution in the cabin.
Location in vehicle
The AQS module must be exposed to a source of external air at all times. The location must be chosen so as to maximize air renewal; dead spaces must be avoided. The best location is in the air intake BEFORE (upstream) the filter. When the flap is closed, it can create a “pocket” of stagnant air; for that reason, the AQS module should not be too “deep in the duct”.
Preferably, the filtering membrane should be facing downward. If this is not possible, it should be vertical, but should never be facing upward, to prevent accumulation of dust
If the AQS module is attached with a bayonet to the air intake wall with its body “in the cabin”, the fixation should be sufficiently air tight so that no air from the cabin is pulled in front of the sensor head.
HVAC unit
Air inlet without AQS
Air
inlet with AQS    Detailed
view
First possibility : bayonet attachment
Second possibility : attachment with plastic snap-in clip
Electrical integration
Connector reference : Tyco C-967642 coding “B”