Magnetic shielding includes products and raw materials for shielding instruments and equipment from magnetic fields. Shielding products for applications requiring a reduction or elimination of interference from magnetic fields. Products include CRT shields, photomultiplier tube (PMT) shields, zero gauss chambers, wire, cable, conduit, sleeving, foil, sheets, and others. They can be used to shield an object, such as a CRT or a PMT, from magnetic fields, or to contain fields from an object that generates a magnetic field.
CRT monitor magnetic shielding is used to prevent image disturbances or monitor "jitter." CRT monitor shields are five-sided boxes constructed of special alloys that protect the monitor from external magnetic fields. Photomultiplier tube (PMT) shields are designed to protect photomultiplier tubes that are exposed to magnetic fields. Shields should be sized to allow an air gap between the shield and the base of the photomultiplier tube. Zero Gauss chambers are constructed of magnetic shielding material and provide a workspace with an extremely low magnetic field. Almost any enclosed geometry can be used as a zero Gauss chamber. Cylindrical chambers are one of the most effective geometries for shielding a confined space. Wire or cable shields are made for wire or cable used in applications requiring high permeability, low coercive forces and ferromagnetic properties. Example applications include strain gages, thermocouples and piezoelectric transducers. Flexible conduit or sleeving is made for cables and wires requiring high permeability magnetic shielding. Custom options may be available by consulting manufacturers. Foils are magnetic shielding material ranging from .002 to .010 inches (.051 to .254 mm) in thickness. Foil provides an effective and inexpensive method of shielding. Sheets are magnetic shielding material ranging from .014 to .062 inches (.356 to 1.58 mm) in thickness. Plates are manufactured of magnetic shielding material, usually .125 inches or more in thickness. Round bar stock is manufactured from magnetic shielding material. Tubing can be manufactured from magnetic shielding material. Lab or sample kits of raw materials contain samples of magnetic shielding material (such as foil and sheets of different thickness). They are intended for experimental use for solving magnetic interference design problems.
Specific parameters important to CRT magnetic shielding are monitor sizes. Common monitor sizes are 17 inch, 19 inch, and 21 inch. Diameter is important when specifying photomultiplier tube magnetic shielding. Foil or sheet thickness can be anywhere from .002 inches to 0.095 inches.