Sampling in motion

An alternative operation to sample the coal is to employ bottom sampling, in which coal is sampled as it is discharged from the bottom of hopper cars. Since the coal is sampled in motion, bottom sampling is considered to be an improvement over car-top sampling. 

In each installation requirements of power, insulation to motion and temperature, and air intake and instrument operation needed specific consideration. Power was usually supplied by a 60-cycle, 110-V gasoline generator except in the aircraft where the 24-V aircraft battery was used. Venturi effects while sampling in motion were controlled by attaching an air baffle at the intake. Temperature stability was achieved by the use of insulation material, and the equipment was carefully mounted on an independent spring suspension to protect it from vibrations. 

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