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Electromagnetic Tag Team
Electric current flow and magnetism interact and either one can induce the presence of the other. If you take a simple bar magnet, place a piece of paper over it, and sprinkle some iron filings on the paper, it looks like the magnet above. The lines of filings represent the magnetic field that is present.
Whenever there is a flow of electricity, there is also a magnetic field that is produced. When an electric field is generated from any AC current flow (at any frequency), the field produced will induce a magnetic field in any magnetic (ferrous) metal that is in the field.
On the other hand, whenever a magnet is moved through a set of electrical conductors, an electric current is generated in the conductors. The larger the field, or movement, or number and size of conductors, the larger the induced magnetism or electric current. An electromagnet can be easily made with a nail with a number of turns of wire wrapped around it. Connect the ends of the wire to a battery, and you have an electromagnet.
Rice Lake offers cable with both foil and more than 90 percent braided shielding.
Take a coil of wire and move a magnet in and out of the coil, and you will generate an electrical voltage at the ends of the wire. All of this becomes vital when dealing with a shielded cable such as a load cell cable or a “home run” cable. The shield must have a low resistance to ground connection on one end only, to act as a shield to any induced electrical current.
Grounding at both ends of the shield provides a resistance between two ground potentials, resulting in a ground loop that can carry enough current to actually damage the equipment to which it is connected.
Shield types are foil, wrapped, braided, or any combination thereof. There are advantages and disadvantages to each, although aside from the cost and flexibility issues, a combination foil and good coverage (over 90 percent) braided shield provides the best protection. All of our SURVIVOR® load cell cable offerings have both foil and more than 90 percent braided shielding.
In addition, the actual ground connection needs to be of very low resistance or the advantages are voided. Good quality connectors and grounding methods (360 degree clamp or solder) are essential.