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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
End Resistance
End resistance (ER) is the resistance measured between the wiper and a reference end terminal when the contact is positioned against the adjacent end stop.
End resistance and minimum resistance are sometimes confused. This is because in many potentiometers the two parameters are identical values with the moveable contact in the same position. The only reason for having two parameters is that the construction techniques of some potentiometers cause two different values. Continuous rotation devices have no end stops, so ER is not specified.
Figure 2.45 shows how MR and ER are calculated.
Figure 2.46
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End resistance is expressed as a maximum value in Ωs, or a maximum percentage of the unit's TR. It is common practice for potentiometer manufacturers to specify MR rather than ER.
NOTE: Care needs to be taken when measuring MR and ER to prevent damage to the element.
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