Capelec EOBD, Руководство пользователя

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23/04/2019 Rev 3 16
II. GAS ANALYZER
II.1. Principle
The gas analyzer is a module dedicated to PTI and automotive workshops. It allows measurement
of carbon monoxide (CO), carbon dioxide (CO
2
), hydrocarbons (HC) in hexane equivalent (C6H14),
and oxygen (O
2
) concentration of the gases from spark-ignition vehicles (petrol, high-octane
petrol, LPG), with or without catalytic converter. As an option, it can be equipped with the NOx kit
allowing nitrogen oxides to be measured.
The CAP3201 also allows the following values to be obtained at any time:
- Calculation of the corrected CO value
- Calculation of Lambda value
- The measurement of rotation speed (measured by induction clip, by battery input …)
- Measurement of oil temperature.
The measurement of CO, CO
2
and HC is carried out using non-diffusing infrared radiation.
The gas passes through a measuring chamber, at the ends of which there are three infrared
detectors and three transmitters. Each transmitter emits a specific wavelength associated with
one of the three gases.
Each of the detectors transmits an electrical signal corresponding to the received radiation
intensity.
Measurement of oxygen concentration is carried out by an active chemical sensor.
ANODE
CATHODE
ELECTROLYTE
O
2
MEMBRANE
ddp
R=f(T°C)
Principle of oxygen measurement:
The oxygen sensor is an electrochemical one; it is based on the principle of electrolysis. In the
presence of oxygen, an ionic current is generated through the cathode, the electrolyte and the
anode, giving rise to a potential difference at the terminals of a resistor, which varies according to
temperature. As a result, the sensor is temperature-compensated.