In addition to the APB® module, the APA includes the HEPA filters for the dilution and saturator flows, the IPA external tank, microprocessor-controlled pumps, a diffusion screen to increase the system d50 up to 23 nm, sampling hose and sampling probe. The APA could also be easily fitted with a second diluter to extend the particle number concentration range to 10,000,000 #/cm3 even though concentration above 250,000 #/cm3 provide reliable indication for defective diesel and gasoline particle filters. An evaporator tube for the removal of the semi-volatile particles is also added to the set up. The simple evaporator tube is operated at nominally 250°C and has a tetracontane removal efficiency of >95%. With the evaporator tube installed, the system can be operated with the evaporator assembly in an active or disabled configuration. This facilitates easy investigations associated with the benefit, for example, reducing the likelihood of reporting a false vehicle PTI failure caused by the intermittent release of semi-volatile nano-particles by the vehicle/engine during testing.
The APA / APB® can be calibrated to fulfil the performance criteria of ISO 27891:2015. However, with the intrinsic linearity and performance predictability of CPC technology, a much-reduced calibration scope could be used (with little or no detrimental effect) with the corresponding significant cost reduction.
APB® test data compares concentrations of 8 test vehicles
APA correlation to reference PMP