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Construction of wirewound resistor
Jan 09, 2018

Construction

Wire wound resistor construction varies widely. The manufacturing and choice of materials used is dependent on the way the resistor will be used in a circuit. All are made by winding a wire around a core. The resistance value is dependent on the resistivity of the wire, the cross section and the length. Since these parameters can be accurately controlled, a high precision can be achieved. For high tolerance requirements, the resistance value is measured to determine exactly the cut to length of the wire. To create a high resistance, the wire diameter needs to be very small and the length very long. Therefore wire wound resistors are mainly produced for lower resistance values. For low power ratings, very thin wire is used. The handling of the wire is for this matter critical. Any damage may sever contact. After winding the wire is well protected from access of moisture to prevent electrolytic corrosion. Next to precision, there are also wire wound resistors with high power rating for 50W or more. These resistors have a quite different construction. Compared to other resistor types as the metal film, the wire diameter is relatively big and therefore more robust.