Bosch BEA 460 Description De Produit page 23

3.5.3 AMM (gasoline exhaust gas module)
1 2
17 16 15 14 13
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Fig. 3: AMM
1 NO2 probe (no function)
2 NO probe (special accessory)
3 O sensor
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4 Activated charcoal filter
5 Pump protection filter GF3
6 Inlet filter GF2
7 Exhaust gas measurement inlet
8 8 m Viton exhaust gas sampling hose (black)
9 Coarse filter GF1
10 30 cm Viton exhaust gas sampling hose (black)
11 Exhaust gas sampling probe
12 Hose connection for leak test
13 Calibrating gas inlet
14 23 cm PVC hose (transparent)
15 23 cm PVC hose (transparent)
16 Gas and condensate outlet
17 Test gas outlet
Robert Bosch GmbH
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3 4 5
459715/8Rf
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Description of unit | BEA 460 | 23
3.6 Description of AMM operation
The AMM is used to measure the gasoline emission
6
components CO, HC, CO
be retrofitted). The excess air factor (Lambda) is
calculated on the basis of the gas values measured.
The non-dispersive infrared method is employed for
measuring the CO, CO
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oxygen component is established by means of an O
sensor with electrochemical action.
3.6.1 Warm-up time
The warm-up time is roughly one minute. Measurements
cannot be taken during this period.
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3.6.2 Zero calibration
At the start of measurement and once measurement
has been started, the BEA performs zero calibration
automatically with ambient air at irregular intervals (the
oxygen measurement drift is monitored and corrected
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if necessary). For zero calibration purposes, the BEA
switches a solenoid valve to ambient air (also referred
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to as zero gas). The system is flushed with ambient air
for 30 seconds. An activated charcoal filter removes the
hydrocarbons from the ambient air drawn in.
i
If measurement is in progress, zero calibration is
postponed until the end of the measurement.
3.6.3 Excess air factor (Lambda) measurement
The BEA calculates the excess air factor (Lambda) from
the measured HC, CO, CO
The Lambda value is calculated with the aid of the
Brettschneider formula:
[ ] Concentration in % by vol, also for HC
K1 Conversion factor for HC from NDIR to FID
(value 8)
HCV Hydrogen/carbon ratio in the fuel
(typically 1.7261) *
OCV Oxygen/carbon ratio in the fuel
(typically 0.0175) *
* Depending on the fuel used. These values can be altered by
Bosch Service.
BEA 460 | 23 | 23
, O and NO (NO can
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and HC components. The
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and oxygen concentrations.
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1 689 989 027 2009-03-26
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