Wetting current

As fritting (English wetting voltage ) refers to an electric voltage, which by proposing a contamination resistance. The case current flowing is called the wetting current, the name is derived from the coherer. Contamination layers can represent at electrical contacts or cable connecting points in this case electrically non-conductive oxides, corrosion, dirt, etc..

The figure shows a resistive voltage characteristic of an occupied with foreign electrical contact layers, if I create this contact to a small voltage, is measured initially a high-resistance contact resistance R0 (several megohms ). If you increase the voltage, the resistance first drops off only slightly. Upon reaching the fritting UF, the resistance breaks down to residual value Rs. The now -adjusting contact voltage U.S. is called Frittschlussspannung.

High Frittspannungen disturbing especially when switching and contact signals with low voltage, as used for example in bus systems or in metrology. They can lead to some hard -to-find errors after a certain running time of the system. By appropriate selection of the contact material, for example gold, the interference effect can be reduced.

Common applications for the fritting among others in the telecommunications sector in the local loop, which are also used as Digital Subscriber Line ( DSL). In order to avoid contact problems on the terminal points of the connecting cable, the standard ITU- T G.992.3 standard, a direct current ( wetting current ) in the range of a few mA is provided to exceed the necessary fritting on all cable terminal points safe.