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Introduction - Basic Potentiometer Theory • Resistors • Building Potentiometers • Modern Variable Resistive Devices • Applications Modes • The Parts of a Potentiometer • Resistive Elements • Cermet • Conductive Plastic • Hybrid Elements • Terminations • Contacts • Electrical Parameters • Total Resistance • Minimum Resistance • End Resistance • Contact Resistance • Contact Resistance Variation • Equivalent Noise Resistance • Output Smoothness • Adjustability • Temperature Coefficient • Resolution • Conformity • Linearity • Power Rating • Summary of Electrical Parameters • Useful Terms
Conductive Plastic
Conductive plastic, the modern carbon film element, is made with a blend of plastic resin and carbon powder. The substrates used are either ceramic or plastic. Conductive plastic material may also be deposited on an insulated metal mandrel and formed in a helix for use in multiturn potentiometers.
In terms of advantages, conductive plastic elements are usually the first choice for an economical way to vary resistance in an electrical circuit. Static and dynamic noise performance are better than that of cermet elements. Due to surface smoothness, conductive plastic elements have a longer rotational life than cermet elements. Like cermet elements, their resolution is essentially infinite.
In terms of limitations, conductive plastic elements have a poorer moisture resistance, temperature coefficient, power dissipation, and wiper current capacity than cermet elements.
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