Chap. I - Gas Analyser
Gas-manual-en.docx — 5 —
4.2 BACK PANEL
1 - Connector (Jack) for the power supply plug
2 - Connector for the computer serial cable
Fig. 2 – View of the back panel of the Gas Analyser
5. CONSTRUCTION OF APPARATUS
5.1 MECHANICAL PART
The device frame is fabricated from steel with a zinc finish, and is coated with a two-compound acrylic paint. The
device case is also fabricated from steel with a zinc protective finish, and sprayed with a wear resistant powder
coated paint. The exhaust probe is made of stainless-steel flexible hose.
5.2 ELECTRONIC PART
The internal electronic system and all clamps, connectors and sensors accessible from the outside are
galvanically isolated, any voltages on them do not exceeding safe levels. The electronics consist of a printed
circuit board, the electronic system of the optical testing bench, and the fan. In the case of the extended version
including engine speed and engine temperature measurement, an additional circuit board is included for these
sensors.
5.3 PNEUMATIC PART
This consists of a double membrane pump with two pumping channels. The P1 channel pumps the exhaust gas
to be measured from the exhaust probe to the optical bench and oxygen sensor (or nitrogen sensor NOx), and
the P2 channel continually empties condensate from the rough filter F1.
The solenoid enables zeroing of the measuring apparatus by switching from the exhaust probe to the zero setting
inlet (which draws in surrounding air). The zero setting inlet includes an active carbon filter F4, which decreases
hydrocarbons which may be present in the surrounding air.
The gas sample measured is subject to double filtration before entry to the optical bench. The first filtration stage
is through a rough filter F1, which is made from sintered bronze grain. The second filtration stage is the fine filter
F2, which is made from paper. Inside the apparatus there is safety filter F3 that protects the solenoid, optics of
the measuring bench, and the oxygen sensor (or nitrogen sensor NOx) in case of incorrect fitting or failure of the
external filters.
The apparatus is also equipped with a calibration inlet CAL, which is used for the connection of the calibration
gas. The pneumatics include a vacuum
switch, which is used for indication of decreased flow through the exhaust
probe from taking in water or blockage, this is also used for the probe leakage test.
The device is equipped with automatic compensation for ambient air pressure.
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