A filter has a filter medium (10) during operation clears fluid, particularly in the form of hydraulic fluid. The filter medium (10) is made of a material such that the potential difference to the fluid to be cleaned is low. The parts of the filter medium (10) have different potentials with respect to each other and/or the fluid to be cleaned such that they cancel each other at least partially, specific dissipation is aspired, or a return of electric charge to the associated filter medium (10) is provided, using a charge equalization situation.