Unlike a compass-needle galvanometer, the astatic galvanometer has two magnetic needles parallel to each other, but with the magnetic poles reversed. The needle assembly is suspended by a silk thread, and has no net magnetic dipole moment. It is not affected by the earth's magnetic field. The lower needle is inside the current sensing coils and is deflected by the magnetic field created by the passing current.astatic galvanometer was developed by Leopoldo Nobili in 1825.[3]