A laboratory comparison of in-line and end-of-line full-flow, diesel smoke opacity meters

A cooperative round robin type program to compare the response characteristics of in-line (NL) and EPA end-of-line (EOL) diesel smoke opacity meters is described. Test results indicated the INL and EOL meters correlated well, agreeing approximately 75% of the time. Best correlation was obtained by using a modified Beer-Lambert expression, i.e., correcting the absorption coefficient for meter emitted light wavelength. The study recommends that future tests consider including detailed optical response characteristics. Further investigation into the use of neutral density filters as calibration standards as well as research to ascertain whether or not the exhaust gas temperature has any effect on smoke correlation are also recommended.