Diesel particle mass concentration by optical techniques

Particle mass concentrations in the exhaust streams of a variety of Diesel engines have been measured using both a visible wavelength opacity meter and an IR photoacoustic device. We present real-time recordings of the emissions from vehicles operated over the Federal Test Procedure driving cycle. Steady-state mass concentrations of a few mg x m(-3) can be measured by opacity and as low as 0.4 mg x m(-3) by the photoacoustic technique, but the uncertainty is approximately 15% in both cases. An uncertainty of approximately 20% is found in the estimation of total mass emission rates over the Federal Test Procedure cycle by integration of the optical signals.