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of electromagnetic waves are widely used in science and technology
comprise a frequency range of electromagnetic radiation, which is limited at the bottom by the radio waves and at the top by the infrared range of the optical spectrum.
Therefore they behave similarly to ordinary light, i.e. they can be reflected, broken and also interfere.
Microwaves are reflected from metals and electrical conductors and only slightly absorbed.
Insulators (e.g. some thermoplastics, especially PTFE (Teflon), glass, many ceramics etc.) are permeable to this radiation and absorb it only a little.
Microwaves have a natural origin (cosmic background radiation), but they have to be generated artificially to make them technically usable, which offers very numerous areas of application for microwaves, especially due to the various sub-ranges within the frequency range.
Runtime tubes (klystrons, traveling wave tubes or magnetrons) are used to generate very high power microwaves.
At low powers, however, gun diodes are used for fixed frequencies and backward wave oscillators for large frequency ranges.
Ferrites absorb microwaves particularly well.
Water-containing substances also absorb microwaves very well - considerably better than dry substances, because because of their wavelength, microwaves are particularly suitable for exciting dipole and multipole vibrations of molecules.
This effect is particularly evident when vibrating water molecules in the microwave oven.
The frequency-dependent absorption of microwaves on or in substances and thus their heating are largely determined by the dielectric loss factor, the specific electrical resistance and magnetic losses.
There are two main areas of application for microwaves in industrial measurement technology: level and moisture measurement.
Two different principles are used for level measurement for continuous measurement or point level detection.
The moisture measurement is based on the analysis of the solid-water mixture in an electromagnetic field.
The influence of the permittivity number of water on the sensor capacity is registered.
Two different methods are used for moisture determination: the transmission method and the reflection method.
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