KBA uses portable emission measurement systems, for both gaseous pollutants (Gas-PEMS) as well as for particles (PN-PEMS), in verification tests, spot checks and field studies. KBA currently has six gas and PN-PEMS combinations.
The mobile measuring systems are mainly used in real road traffic to carry out real driving emissions (RDE) tests. Measurements are carried out under the conditions of Regulations (EC) numbers 715/2007 and 2017/1154 as well as additional, case-related tests.
KBA is thus able to randomly examine vehicles in the field with the mobile exhaust emission measuring devices and determine any prohibited defeat devices.
The mobile exhaust emission measuring device is usually mounted upon a support structure on the connecting device of the test vehicle.
Extensive adjustments are sometimes required in order to connect the vehicle's exhaust system to the PEMS. A gas-tight connection must be established. The entirety of exhaust gas from the test vehicle is routed through the Exhaust Flow Meter (EFM) as part of the PEMS. A schematic representation of the measurement principle is given below.
If vehicles do not have a coupling device, the gas PEMS is placed in the trunk. In this case, the EFM for measuring the exhaust gas mass flow is fixed to the rear of the vehicle by a steel frame, which is attached to the body and to the towing eye respectively. The heated sampling line leads a partial flow of the exhaust gas to the analysers of the portable emission measuring system. The Kraftfahrt-Bundesamt (KBA) has the option of equipping each vehicle type with the PEMS individually.
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:
NO (nitrogen monoxide), NO2 (nitrogen dioxide), NOx (calculated sum of NO + NO2)
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.