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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
Temperature Coefficient
The Temperature Coefficient (TC) indicates the maximum change in total resistance (TR) due to a change in operating temperature. TC is specified as PPM/ °C, where PPM means "parts per million."
To determine the TC for a particular unit, measure its TR for two ambient temperatures. Then place the values into this formula:
The resulting TC will be in PPM/ °C.
Temperature coefficient depends on the material used in the resistive element.
Cermet elements have a TC of ±100PPM/ °C.
Wirewound elements have a TC of ±50PPM/ °C.
Conductive plastic elements have a TC of ±1000PPM/ °C.
Given the information above, if a customer indicates that he has a tight TC requirement, which type of element should you recommend?
(The correct answer is wirewound, though cermet elements have a good TC and could meet most requirements.)
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