To be understood under the term "sampling" are all work procedures necessary to remove a quantity of samples in such a manner that they largely correspond to the total quantity with regard to quality and without systematic errors.
Subsequent "sample preparation" includes all requisite work procedures to bring the sample material obtained in sampling into the condition prescribed for the subsequent examinations.
To be taken into account in subsequent sample preparation is that the collection sample from the individual samples reflects the homogeneity of the material to be sampled. In all work procedures, special care is required to ensure that the sample is prepared without loss of characteristics worth mentioning (e.g. water content).
The high requirements to be made on the technical execution of machinery and equipment for sampling and sample preparation arise, inter alia, from the very high proportion of the material quantity to be examined to the total amount to be assessed. This can be explained using the example of ash content.
Taking a representative sample from material that is stationary involves very great difficulties and almost invariably can only be realised in a limited manner.
The average sample to be taken for sampling ("random sample" in the statistical sense) comprises individual samples, the number of which depends on the material quantity to be assessed and on the dispersion of the characteristics to be determined within the material quantity.
Should several quality characteristics have to be determined, the strongest dispersing characteristic is decisive for defining the number of individual samples. When planning and executing such plants for sampling and sample preparation, the manufacturer should take special care to ensure that all machinery and equipment operate without systematic errors, and that deviations that may occur, for example, when separating sample material are as low as possible.