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In pneumatic conveying, solid particles such as flour or coal are carried through a duct by a moving air stream. Solids density at any duct location can be measured by passing a laser beam of known intensity I„ through the duct and measuring the light intensity transmitted to the other side, 1. A transmission factor is found by
T = t/!o= e~KEW 0 < 7 < 1
Here IV is the width of the duct, K is the solids density, and E is a factor taken as 2.0 ± 0.04 (95%) for spheroid particles. Determine how uk/K is related to the relative uncertainties of the other variables. If the transmission factor and duct width can be measured to within ±1%, can solids density be measured to within 5%? 10%? Discuss your answer, remembering that the transmission factor varies from 0 to 1.
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Theory and Design for Mechanical Measurements
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