In Germany, the measurement of the particle concentration in diesel exhaust gas is governed by the Measures and Verification Act. The measuring instruments used for this purpose have to meet specific requirements. Such particle counters must, for instance, be tamper-proof, stable and robust to disturbances, and they must obviously provide correct measurements. In Germany, PTB’s CAB is the only entity to check that these requirements are met and to document this within the scope of a type examination carried out on a representative particle counter. The tests performed include checking whether the maximum permissible error limit is complied with and whether the particle counter performs measurements fast enough. Tests are also carried out to ensure that particle counters work reliably in hot and cold environments and to make sure that electromagnetic disturbances – e.g., from cell phones – have no influence on the measured values.

The main requirements placed on such particle counters are specified in the Measures and Verification Ordinance. The details concerning concrete implementation are recorded in the PTB requirements developed over the past few years with the participation of all relevant stakeholders (i.e., representatives of the competent ministries, the Federal Highway Research Institute (Bundesanstalt für Straßenwesen – BAST), organizations responsible for testing, associations of manufacturers and end-users, weights and measures offices, PTB). These requirements were published in May 2021.

The first three measuring instruments have passed all mandatory tests and have therefore been issued a type-examination certificate. Further measuring instruments are currently being tested.