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Electromagnetic Tag Team
Electric current flow and magnetism interact, and either one can induce the presence of the other.
What Is a Magnetic Field?
To see a magnetic field, take a simple bar magnet, place a piece of paper over it and sprinkle some iron filings on the paper. The lines of the filings represent the magnetic field present.
Whenever there is a flow of electricity, a magnetic field 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 in the field.
However, when a magnet is moved through a set of electrical conductors, an electric current is generated in the conductors. The larger the field, movement, or number and size of conductors, the larger the induced magnetism or electric current.
What Is an Electromagnet?
An electromagnet can be easily made with a nail and several turns of wire wrapped around it. Connect the ends of the wire to a battery, and you have an electromagnet.
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. This becomes vital when dealing with a shielded cable such as a load cell cable or a “homerun” cable. The shield must have a low resistance to the ground connection on one end only to act as a shield to any induced electrical current.
Grounding at both ends of the shield provides resistance between two ground potentials, resulting in a ground loop that can carry enough current to damage the equipment to which it is connected.
Shield types are foil, wrapped, braided or a combination. Each has advantages and disadvantages, although aside from the cost and flexibility issues, a combination of foil and braided shield with 90% coverage provides the best protection.
In addition, the actual ground connection needs to be very low resistance or the advantages are voided. Good-quality connectors and grounding methods (360-degree clamp or solder) are essential.
Rice Lake Solutions and Support
Rice Lake Weighing Systems’ SURVIVOR® cable comes with both foil and more than 90% braided shielding. For more information on grounding and load cells, contact your Rice Lake scale technician.