Division 5.7.2 Calibration/validation of the VPR

N_in(d_i) and N_out(d_i) shall be corrected to the same conditions.

The arithmetic average particle concentration reduction factor $\bar{f_{r}}$ at a given dilution setting shall be calculated using the following equation:

\bar{f_{r}} = \frac{f_{r} (30nm) + f_{r} (50nm) + f_{r} (100nm)}{3}

Where a polydisperse 50 nm aerosol is used for validation, the arithmetic average particle concentration reduction factor $\bar{f_{v}}$ at the dilution setting used for validation shall be calculated using the following equation:

\bar{f_{v}} = \frac{N_{in}}{N_{out}}

where:

N_in

is the upstream particle number concentration;

N_out

is the downstream particle number concentration.

5.7.2.1Calibration of the VPR’s particle concentration reduction factors across its full range of dilution settings, at the instrument’s fixed nominal operating temperatures, shall be required when the unit is new and following any major maintenance. The periodic validation requirement for the VPR’s particle concentration reduction factor is limited to a check at a single setting, typical of that used for measurement on particulate filter-equipped vehicles. The approval authority shall ensure the existence of a calibration or validation certificate for the VPR within a 6-month period prior to the emissions test. If the VPR incorporates temperature monitoring alarms, a 13 month validation interval is permitted.
5.7.2.2The test aerosol for these measurements shall be solid particles of 30, 50 and 100 nm electrical mobility diameter and a minimum concentration of 5 000 particles per cm3 at the VPR inlet. As an option, a polydisperse aerosol with an electrical mobility median diameter of 50 nm may be used for validation. The test aerosol shall be thermally stable at the VPR operating temperatures. Particle number concentrations shall be measured upstream and downstream of the components.
5.7.2.3Division 5.7.2.3