Astatic needles
File:Galvanometro astatico di tipo Nobili inv 1417 IF 38380.jpg
An astatic system comprises two equal and parallel magnetic needles, but with their polarities reversed. This arrangement protects the system from the influence of the terrestrial magnetic field, as the magnetisms of the two needles cancel each other out. Because of this phenomenon, astatic needles were often used in galvanometers.
References
- {{Cite web|url=http://catalogo.museogalileo.it/approfondimento/AghiAstatici.html|title=Museo Galileo - object description|last=|first=|date=|website=|publisher=|access-date=}}
- {{Cite web|url=https://www.princeton.edu/ssp/joseph-henry-project/galvanometer/astatic-needles/|title=Static Needles - Joseph Henry Project - Princeton University|last=|first=|date=|website=|publisher=|access-date=}}
Category:Historical scientific instruments
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