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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
Contact Resistance
Contact resistance (CR) is the resistance that exists in the electrical path from the wiper terminal's contact with the resistive element. CR is a function of the materials selected for the wiper and the resistive element, as well as the pressure that exists between the two.
Contact resistance can be demonstrated by the simple three-step experiment shown in Figure 2.47.
Figure 2.47
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If we measure the resistance between pins 1 and 2, then 2 and 3, and add them together, the sum is greater than the device's total resistance! This is due to the contact resistance between the moveable contact and the resistive element.
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