| abstract |
Sample air is divided into two paths. One path leads through a thermal converter where ambient NO 2 is changed into NO. The other path passes through equivalent tubing to keep the air samples synchronized. Both samples then go to separate cells where each combines with ozone. The resulting chemical reaction produces light, chemiluminescence, which is measured by separate photo-multiplier tubes. Electronic circuits translate the results into simultaneous readings of NO x and NO concentrations. A difference amplifier subtracts the NO from the NO x to give a continuous NO 2 value. |