An understanding of exhaust processes, especially during unsteady engine operation, greatly assists in achieving emission goals. Conventional~i.e., integral~measurement systems only provide lump-sum, final values at the end of a given interval, or instantaneous rate values during steady-state operation.The paper presents a system for measuring instantaneous emission values during unsteady engine operation. The system is designed for installation in commercial vehicles, it is resistant to vibration, and it does not affect fuel consumption.The equipment includes infrared CO analyzers with transistorized sensors, rather than gas-filled receptor chambers which are sensitive to vibration. Mass flow rates of inlet combustion air rather than exhaust are measured, due to temperature fluctuations of exhaust. The produced electric signals are amplified, corrected, and filtered before they are processed to provide read-out emission values. Measuring deficiencies which tend to delay and reduce peak values can be overcome by the incorporation of proportional-differential electronic circuits.