Capelec EOBD, Руководство пользователя

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23/04/2019 Rev 3 39
III. SMOKE-METER
III.1. OPERATING PRINCIPLE
In the composition of the exhaust gas emitted by diesel engines, the pollutant component is
considered to be carbon in suspension. A polluting vehicle emits on acceleration a puff of gas that
is darker (and thus more opaque) than a vehicle in good conditions. The partial flow opacimeter is
used to give a measure of this phenomenon based on a given measure unit called K (m
-1
).
The principle of opacity measurement is the following: a beam of light (transmitter aimed at a
receiver, with a constant distance between the two) is passed through a sample of gas. The
fraction of incident light which reaches the receiver is inversely proportional to the concentration
of particles in suspension in the gas.
The measurement obtained is digitally corrected.
The opacity of a vehicle is the maximum opacity value measured during free acceleration cycle.
3
4
5
1
2
6
7
Air pur
Gaz d'échappement
8
1- Transmitter
2- Receiver
3- Temperature sensor chamber
4- Heating elements
5- Gas temperature sensor
6- Gas inlet
7- Measurement chamber
8- Exhaust fan
Measurement chamber diagramm.
The opacimeter depends on the interactive operation of two sub-systems. The first is composed
of the cell. This is what establishes the opacity measurement. The electronic system of this cell
contains a microprocessor which makes it possible, on the basis of several temperature and
pressure sensors, to regulate the system, to detect bad operating conditions and to correct the