Measuring Principle (PEMS)
The EFM and the control box measure the vehicle’s flow rate and the exhaust gas temperature. The heated sampling line takes a partial volume flow (2 l/min) and feeds it to the PEMS. A system computer ensures the connection to the entire system components. The measurement data is saved on the integrated hard drive. The mobile exhaust emission measuring system is able to detect different exhaust gas components:
| NDUV1 analyser: | NO (nitrogen monoxide), NO2 (nitrogen dioxide), NOx (calculated sum of NO + NO2) |
| NDIR2 analyser: | CO (carbon monoxide), CO2 (carbon dioxide) |
| O2 sensor: | O2 (oxygen) |
1 Non-dispersive UV absorption photometry
2 Non-dispersive infrared sensor
In addition to the gaseous exhaust gas components that are detected with the PEMS, the solid exhaust gas components can be detected with an additional particle PEMS (PN-PEMS). The PN-PEMS counts the number of particles in the exhaust gas. To determine the ambient conditions, a so-called weather station is placed on the vehicle. The weather station measures the relative humidity and the air temperature. With the help of a GPS sensor, which is also mounted on the vehicle roof, the vehicle speed and meas-urement route’s course are determined. |
The following figure illustrates the measuring principle of the PEMS (without PN-PEMS):
The extracted raw gas is cleaned of particles by a filter. The exhaust gas is then passed through the respective measuring devices and analysed.