TECNOMOTOR 820 Manual Operativo página 41

2 GENERAL INFORMATION
820, 840 and 840 Plus opacimeters have been type approved for conformity with Italian Ministerial
Decree 628/96 of 23 October 1996. The opacimeter you have purchased has also been type approved
for compliance with the new circular of the Italian Ministry of Transport and Navigation n° 88/95 of 6
September 1999 published in the ordinary supplement to the Italian Official Journal "Gazzetta
Ufficiale" no 229.
3 MEASURING MODULE
Opacimeters are designed to measure the pollutant emissions of a diesel vehicle. The instrument is
partial flow type, namely it can measure smoke opacity by taking a sample of the exhaust gases
emitted by means of a sampling probe which is introduced into the vehicle tail pipe. Tests carried out
have shown that the probe specific shape does not significantly alter neither the normal flow of the
vehicle exhaust gases nor the engine operation in any way. Furthermore, inserting the probe inside the
exhaust pipe completely eliminates the risk that the measurement can be influenced by the external air
or by small infiltrations due to counter-pressure that may be present in the outlet close proximity.
Therefore, the exhaust gases collected enter the analysis module, where a specific measuring system
based on the absorption of light intensity, performs the measurement.
4 Operating principle
The operating principle on which the opacimeter is based is the light beam intensity attenuation,
caused by the optical absorption by solid (particulate matter) and gaseous particles contained in the
exhaust gas and by the radiance effect. A light source, consisting of a LED, produces a light beam
that passes through the centre of the exhaust gas column, where part of the light is absorbed, so that
the light intensity reaching the receiver is attenuated. The receiver sensitive element is a photodiode.
The difference between the electrical signal produced by the receiver in the absence of exhaust gas
and the signal produced when the exhaust gas enters the measuring chamber, gives a measure of the
light intensity absorbed by the exhaust gas column and therefore allows calculating its opacity.
Opacity is conventionally measured as a percentage (of light attenuation), but this value depends on
the optical path of the light beam. In order to free from the optical path, the unit of measurement k
(absorption coefficient) expressed in m¯ ¹ according to Lambert Beer's law is used.
5 WARRANTY
Here following the warranty terms and conditions, unless otherwise specified in the Order
confirmation:
5.1.1 Subject of Warranty
THE BUILDER guarantees the good quality and good construction of the machines
manufactured; committing itself, during the specified warranty period, to repair or replace
free of charge parts which would get broken or worn prematurely due to poor quality of the
materials used, manufacturing defects or imperfect assembly.
The guarantee is not applied in case of parts which would get broken or worn due to:
- Failure to comply with the instructions contained in the Use and Upkeep Manual.
- Lack of or incorrect upkeep
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