The measuring methods with which the moisture in a product can be determined are very diverse. There are approximately ten measuring methods for determining the moisture content of solids (so-called material moisture measuring method) and about 15 measuring methods for the gas moisture measurement (so-called gas moisture measurement method). All gas moisture measurement methods are also suitable for material moisture measurement. A distinction is made between direct and indirect measurement methods. The direct material moisture measurement methods provide an immediate indication of the water content in the material to be measured (reference methods), but they can hardly be used online. The indirect material moisture measurement methods give a statement on the moisture properties of the material to be measured. They can be used online, but require a comparison to the respective product (material-specific characteristic).