ABSTRACT
Some mechanical sampling systems take only a particular section of a moving stream and this is not considered satisfactory. There is a widespread belief that, as with modern instrumentation in chemical laboratories, the installation of any kind of automatic electronic equipment is foolproof. The most important component of a mechanical sampling system is the primary sampler. Conventionally, the width of the sampling aperture is a minimum of three times the nominal top size of the coal being sampled. It cannot be stressed too strongly that regular tests must be performed on such installations in order to prevent sample bias. The danger of applying statistical formulae to the measurement and checking of the precision of the performance of primary samplers in mechanical systems is that they make certain assumptions which are not always valid.
