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13 General information concerning moisture analysis
13.1 Application
In all cases where moisture is added to or removed from products, a fast
determination of the moisture content is of enormous importance. For countless
products the moisture content is not only a quality feature but also an important cost
factor. Very often fixed limits for moisture content apply to the trade in industrial or
agricultural goods as well as chemical or food products which are defined by terms of
delivery and general standards.
13.2 Basics
The Halogen Moisture Analyzer is used to determine the moisture content of almost
any substance. The instrument works according to the thermogravimetric principle. A
halogen lamp dries the sample substance that is being examined, while the precision
balance integrated in the instrument continuously measures the weight of the
sample. In the process, the total weight loss will be interpreted as moisture content.
The main benefit of using a halogen lamp is the shortening of the measuring time
compared to conventional drying methods. In addition, the sample is heated very
evenly by the radiant heater, as it is positioned in a ring above the sample material.
This results in very good repeatability of the measurement result. The basis for
calculating the moisture content is the amount of weight the sample has lost when
drying is complete. Final results, intermediate results, procedures and method
parameters can be documented by connecting an optional printer.
13.3 Drying process
The conventional drying chamber method follows the same principle, with the
exception that this method requires a considerably longer measuring period. . In
accord with the drying chamber method, the sample is heated from the outside to the
inside by a hot air current, so as to remove the moisture. The radiation applied in the
KERN DAB penetrates mainly the sample in order to be transformed inside it into
heat energy that is, warming from the inside to the outside. A minor amount of
radiation is reflected by the sample, a reflection that is less in dark samples than in
light-coloured ones. The depth of penetration of the radiation depends on the
permeability of the sample. For samples with low transmittance, the radiation only
penetrates the upper layers of the sample, which can lead to incomplete drying, the
formation of a crust or burnt areas. For that reason the preparation of a sample is of
great importance.
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