Abstract: The combination of ambient air, exhaust and premeasured calibration gases is used according to this invention in the analysis of either low or high pollutant concentration gases measured by a single range analyzer. By using ambient air as a diluent and employing its concentration values to generate the Reference Dilution Ratio, DR.sub.ref, iterative calculations are made to find the Raw Sample Concentration value, C.sub.raw. The gas diluting/mixing system includes pressure balanced infeed plumbing legs. Each of the legs feeds to respective flow restrictors and a common, downstream mixing "T" fitting. One leg is interconnected to the high concentration emission gas output from the sampling system and high concentration calibration gas. The other leg is interconnected to the diluent gas source, ambient air.

Abstract: Apparatus for retaining contact of a wheel having a first and second sidewall includes a first roller having a tapered body, the tapered body of the first roller having a larger diameter at the first sidewall of the wheel and having a constant or curved taper to a smaller diameter towards the second sidewall of the wheel. The apparatus further includes a second roller having a tapered body, the tapered body of the second roller having a larger diameter at the first sidewall of the wheel and having a constant or curved taper to a smaller diameter towards the second sidewall of the wheel, the first and second rollers being disposed adjacent to each other, wherein the taper of the first and second rollers enables the rollers to maintain contact with the wheel at varying rotational speeds.

Abstract: A brake test method measures the brake force per axle of a vehicle by having an operator linearly depress the vehicle brake pedal while the axle's left and right wheels positioned on torque motor driven, constant speed rollers. The roller drive torque magnitude is periodically sampled and the samples are filtered to remove ovality discontinuities, the left and right side filtered samples are then compared to detect the maximum brake force imbalance.