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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
Application Modes
There are two application modes for a potentiometer:
- the variable voltage divider mode
- the variable current control, or rheostat mode
Let's examine each one.
The variable voltage divider mode provides an output voltage that is in reduced proportion to the voltage applied to its input. In its simplest form, it consists of two resistances in series. The input voltage is applied across the total circuit and the output voltage is developed across one of the individual resistances. Figure 2.37 is a circuit diagram of the basic variable voltage divider.
Figure 2.37
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The voltage divider mode is the most common application of any 3-terminal potentiometer. The variable current control (rheostat) mode uses the variable resistance. The variable current control (rheostat) mode uses the variable resistance between the wiper terminal and one end terminal as a means to control current flow. Figure 2.38 illustrates the basic circuit arrangement.
Figure 2.28 shows a fiberboard or ceramic bar mandrel.
Figure 2.38
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