The source of and a simple way to avoid ground loops in biasing Langmuir probe array

Biasing multiple Langmuir probes arranged in an array through one voltage source presents a more compact, reliable and convenient way to bias than using an individual source for each probe. This approach however is the subject of ground loops and several methods have been discussed to avoid them. The high frequency isolation transformer is considered to be a best way to break ground loops since it does not require an additional power supplies and, in general, any other electric circuit. The presented results demonstrate a considerable suppression of the ground loop noise using this technique. The following limitations should be considered in this approach: only an AC voltage bias should be applied, the relatively high internal resistance of the transformer should be taken into account, the frequency of the AC bias signal should correspond to the transforner bandwidth.