a variety of ohmic valu example, VIN = VR1 + VR2.
Potentiometer Example No1
A resistor of 250 ohms is connected in series with a second resistor of 750 ohms so that the 250 ohm resistor is connected to a supply of 12 volts and the 750 ohm resistor is connected to ground (0v). Calculate the total series resistance, the current flowing through the series circuit and the voltage drop across the 750 ohm resistor.
potentiometer example one
Β
Explanation:
uman ear has a logarithmic response and is therefore non-linear.
If we where to use a linear potentiometer to control the volume, it would give the impression to the ear that most of the volume adjustment was restricted to one end of the pots track. The logarithmic potentiometer however, gives the impression of a more even and balanced volume adjustment across the full rotation of the volume control.
So the operation of a logarithmic potentiometers when adjusted is to produce an output signal which closely matches the nonlinear sensitivity of the human ear making the volume level sound as though it is increasing linearly. However, some cheaper logarithmic potentiometers are more exponential in resistance changes rather than logarithmic but are still called logarithmic because their resistive response is linear on a log scale. As well as logarithmic potentiometers, there are also anti-logarithmic potentiometers in which their resistance quickly increases initially but then levels off.
The all potentiometers and rheostats are available in a choice of different resistive tracks or patterns, known as laws, being either linear, logarithmic, or anti-logarithmic. These terms are more commonly abbreviated to lin, log, and anti-log, respectively.
The best way to determine the type, or law of a particular potentiometer is to set the pots shaft to the center of its travel, that is about half way, and then measure the resistance across each half from wiper to end terminal. If each half has more or less equal resistance, then itβs a Linear Potentiometer. If the resistance appears to be split at about 90% one way and 10% the other then chances are itβs a Logarithmic Potentiometer.
Potentiometer Summary
In this tutorial about potentiometers, we have seen that a potentiometer or variable resistor basically consists of a resistive track with a connection at either end and a third terminal called the wiper with the position of the wiper dividing the resistive track. The position of the wiper on the track is adjusted mechanically by rotating a shaft or by using a screwdriver.
Variable resistors can be categorised into one of two operational modes β the variable voltage divider or the variable current rheostat. The potentiometer is a three terminal device used for voltage control, while the rheostat is a two terminal device used for current control.
We can summarise this in the following table:
TypePotentiometerRheostat
Number of
ConnectionsThree TerminalsTwo Terminals
Number of TurnsSingle and Multi-turnSingle-turn Only
Connection TypeConnected Parallel with a Voltage SourceConnected in Series with the Load
Quantity ControlledControls VoltageControls Current
Type of Taper LawLinear and LogarithmicLinear Only
Then the potentiometer, trimmer and rheostat are electromechanical devices designed so that their resistance values can be easily changed. They can be designed as single-turn pots, presets, slider pots, or as multi-turn trimmers. Wirewound rheostats are mainly used to control an electrical current. Potentiometers and rheostats are also available as multi-gang devices and can be classified as having either a linear taper or a logarithmic taper.
Either way, potentiometers can provide highly precise sensing and measurement for linear or rotary movement as their output voltage is proportional to the wipers position. The advantages of potentiometers include low cost, simple operation, lots of shapes, sizes and designs and can be used in a vast array of different applications.
However as mechanical devices, their disadvantages include eventual wear-out of the sliding contact wiper and/or track, limited current handling capabilities (unlike Rheostats), electrical power restrictions and rotational angles that are limited to less than 270 degrees for single turn pots
