Magnetic compensation systems, also called magnetic cancellation or active compensation systems, were especially developped to reduce low frequency magnetic strayfields. With those compensation- / cancellation systems, electron microscopes, electron beam lithography oder other tools, based on electron- or focused ion beams are safely protected from those stray fields.

Compensation systems typically reduce lowe frequency magnetic fields in freqiency range between 0.01 Hz up to 1000 Hz. However, some systems are able to cancel higher frequencies, too. Those magnetic fields are typically caused by moving cars, tramways, elevators, sweeping magnets, railways, electrocal installations like transformers, switch gear, busbars and overhead lines. 

Compensation systems work best in homogenous fields with low gradients. This applies typically to remote sources like tramway, railway and overhead lines, meaning, cancellation of the fields of local sources such as busbears, cables and tranformers is somewhat limited.