CRT with coil measuring stray magnetic fields - and controlling current in compensating coil also around outside edge of screen

摘要

The c.r.t. has measuring and compensating coils wound around it. The compensating coil carries a current whose magnitude, phase and shape are chosen to compensate the effects of stray magnetic fields. This compensating current is chosen by referring to the current generated in the measuring coil as a result of the spray magnetic fields. The compensating coil is wound around the outside of the screen part of the tube just behind the measuring coil. The coils compensate for the effect of unwanted fields parallel to the tube's long axis.