Potentiometers and Rheostats

EGR 101 1

Variable Resistors -- Potentiometers

• Potentiometer – a three-terminal resistor whose value can be adjusted (within set limits) by the user

• Rac = Rab + Rbc

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Construction

3EGR 101

Setting the Value of Resistance

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Potentiometer Taper

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Linear – resistance varies at a constant rate

Nonlinear – resistance changes at an increasing rate

Potentiometer Ratings

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Resistance Rating

Printed in straightforward manner: 5 k

Printed as code: 502 = 50 x 102 = 5 kFirst two digits are the digits in the resistance valueThird digit – number of zeros

Power Dissipation Rating – consult manufacturer's catalog

Trimmer Potentiometers

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low-power applications

Multiturn Potentiometers

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Much better resolution

Smaller percentage of change per degree of rotation

Gang – Mounted Potentiometers

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Two pots share the same control shaft

Rheostats

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A variable resistance used to control current

Usually a two-terminal variable resistor

Potentiometer can be wired as a rheostat

Rheostats

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