Date of Graduation


Document Type


Degree Type



Statler College of Engineering and Mineral Resources


Mechanical and Aerospace Engineering

Committee Chair

Marc Besch

Committee Co-Chair

Ross Ryskamp

Committee Member

Arvind Thiruvengadam


Constant Volume Sampling (CVS) systems are an approved method for emission testing as stated in CFR Title 40 Part 1065 Engine Emission Testing Program. For future near zero emission vehicles, the emission measurement equipment must verify the results with the same accuracy as the limits in the past. The most critical values are the limitations for THC, NOx and particulate matter.

The objective of this study was aimed at identifying challenges associated with measuring system-out emissions at proposed ultra-low NOx (ULNOx) levels - 0.02 (g/bhp-hr) and system robustness. The study compared a variety of existing instrument technologies for addressing the question of suitability of these instruments in satisfying the measurement accuracy standards at ULNOx levels. In addition to the conventional automotive grade instrument (MEXA-ONE) an MKS MultiGas 2030HS and two other standalone low ppm NOx instruments used in continuous emissions monitoring systems (CEMS), were also included (Brandgaus 7705 and Ecophysics CLD64). This study addressed linearity, drift, cycle-by-cycle performance, low concentration performance, and signal noise at various concentrations.

The study showed that the Ecophysics CLD64 outperformed the conventional MEXA-ONE during low concentration steady state ambient NOx conditions (<7 >ppb) while the Brandgaus 7705 and MKS MultiGas 2030HS reached their detection limits at 0.02 and 0.5 ppm respectively. The study also showed that NO2 has negative effects on CLD analyzers regardless of photomultiplier tubes or solid-state photodiode detector technology. In summary, the study compared such analyzers in various conditions and addressed their respective uses in future ULNOx environments.