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Potentiometer – Definition, Working Principle, Types

  • Last Updated : 27 Sep, 2021

An electric flow is a surge of charged particles, like electrons or particles, travelling through an electrical channel or space. It is estimated as the net pace of stream of electric charge through a surface or into a control volume. The moving particles are called charge transporters, which might be one of a few sorts of particles, contingent upon the transmitter. In electric circuits, the charge transporters are frequently electrons travelling through a wire. 

In semiconductors, they can be electrons or openings. In an electrolyte, the charge transporters are particles, while in plasma, an ionized gas, they are particles and electrons.  The SI unit of electric flow is the ampere, or amp, which is the progression of electric charge across a surface at the pace of one coulomb each second. The ampere is a SI base unit Electric flow is estimated utilizing a gadget called an ammeter.  Electric flows make attractive fields, which are utilized in engines, generators, inductors, and transformers. In customary conductors, they cause Joule warming, which makes light in glowing lights. Time-changing flows produce electromagnetic waves, which are utilized in media communications to communicate data.

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Potentiometer

A potentiometer is an electronic device that measures the EMF (electromotive force) of a cell as well as the cell’s internal resistance. It’s also used to compare the EMFs of various cells. In most applications, it may also be used as a variable resistor. 

These potentiometers are widely employed in the production of electronics equipment that allows users to alter electrical circuits to achieve the desired outputs. Although its most obvious application must be for volume controls on radios and other audio-related electronic equipment.

Potentiometer Pin Out:

The Trimpot potentiometer’s pin diagram is given below. These potentiometers come in a variety of forms and have three leads. These components are simple to install on a breadboard for prototyping. This potentiometer has a knob on top of it that may be turned to adjust the value.

  • Pin 1 (Fixed End): This fixed end1 can be connected to one of the resistive path’s ends.
  • Pin 2 (Variable End): This changeable end can be connected to the wiper to give variable voltage.
  • Pin 3 (Fixed End): This second fixed end can be connected to the resistive path’s other finish.

Necessities for the selection of Potentiometer

Potentiometers come in a variety of shapes and sizes, and their selection is based on specific requirements such as the ones listed below.

  • The Structure’s requirements
  • Resistance to Change Characteristics
  • Choose a potentiometer based on the needs of the application.
  • Choose the settings based on the circuit’s requirements.

Construction of a Potentiometer

A potentiometer comprises a long wire with a uniform space of the cross area. Normally the wire is comprised of manganin or constantan. Sometimes the wire might be cut into certain pieces and each piece is associated toward the end focuses through a thick metallic strip. Typically it will be copper strips. Each piece of wire has a length of one meter. For the most part, there will be six bits of wire and the all-out length of the wire is six meters. For the most part the length of the wire shifts from 4 m to 10 m. The more the length of the wire, the better the precision of the potentiometer.  

The potentiometer comprises a driving circuit that comprises a battery, key and rheostat. It additionally comprises a galvanometer and a rider. The end focuses or the terminals of the potentiometer are associated with the focuses where the potential contrast is to be estimated.



Construction of Potentiometer

Working Principle of Potentiometer

The fundamental working standard of this depends on the way that the fall of the potential across any piece of the wire is straightforwardly relative to the length of the wire if the wire has a uniform cross-sectional region and the consistent flow moving through it. “When there is no expected distinction between any two hubs there is electric flow will stream”.  

Presently the potentiometer wire is really a wire with high resistivity (ρ) with uniform cross-sectional region A. Accordingly, all through the wire, it has uniform opposition. Presently this potentiometer terminal associated with the phone of high EMF, V (ignoring its inside opposition) is called the driver cell or the voltage source. Let the current through the potentiometer is I and R is the all-out obstruction of the potentiometer.

Then by Ohms law: 

V = IR

We know that 

R = ρL/A

Thus, 

V = I ρL/A

As ρ and A are always constant and current I is kept constant by a rheostat.

So 



L ρ/A = K (constant)

As a result, 

V = KL

Assume that a cell E with a lower EMF than the driver cell is added to the circuit as indicated. Let’s say it’s EMF, E. The potentiometer has now become E in the potentiometer wire, say at length x.

E = L ρx/A= Kx

When this cell is connected to the appropriate length (x) in the circuit illustrated above, no current will flow through the galvanometer since the potential difference is equal to zero. As a result, the galvanometer G displays null detection. The length (x) is then referred to as the null point’s length. Now that you have the constant K and the length x, you can solve the problem. We’ll be able to locate the mysterious EMF.

E = L ρx/A=Kx

Second, the EMF of two cells may be compared by assuming that the first cell of EMF, E1 has a null point at length L1 and the second cell of EMF, E2 has a null point at length L2.

Then,

E1/E2= L1/L2

Types of Potentiometers

A potentiometer is additionally normally known as a pot. These potentiometers have three terminal associations. One terminal is associated with a sliding contact called a wiper and the other two terminals is associated with a decent obstruction track. The wiper can be moved along the resistive track either by utilization of a straight sliding control or a revolving “wiper” contact. Both turning and direct controls have similar fundamental activities.  

The most well-known type of potentiometer is the single turn rotational potentiometer. This sort of potentiometer is frequently utilized in sound volume control (logarithmic shape) just as numerous different applications. Various materials are utilized to build potentiometers, including carbon structure, cermet, conductive plastic, and metal film.

  • Rotary Potentiometers:

These are the most widely recognized sort of potentiometers, where the wiper moves along a roundabout way. These potentiometers are principally used to get a variable voltage supply to a negligible portion of circuits. The best illustration of this turning potentiometer is a radio semiconductor’s volume regulator where the pivoting handle controls the current stock toward the intensifier.  

This sort of potentiometer incorporates two terminal contacts where a predictable obstruction can be situated in a semi-roundabout model. And furthermore, it remembers a terminal for the centre that is partnered to the opposition utilizing a sliding contact that is associated through a turning handle. The sliding contact can be turned by turning the handle over the half-roundabout obstruction. The voltage of this can be gotten among the two contacts of obstruction and the sliding. These potentiometers are utilized at any place level voltage control is essential.

  • Linear Potentiometers:

In these kinds of Potentiometers, the wiper moves along a straightway. Otherwise called slide pot, slider, or fader. This potentiometer is like the rotational sort however in this potentiometer, the sliding contact basically turned on the resistor directly. The association of the resistor’s two terminals is associated across the voltage source. A sliding contact on the resistor can be moved to utilize a way that is associated with the resistor.  

The terminal of the resistor is associated with the sliding which is associated with one completion of the circuit’s yield and one more terminal is associated with the other completion of the circuit’s yield. This sort of potentiometer is for the most part used to ascertain the voltage in a circuit. It is utilized to quantify the battery cell’s inside opposition and furthermore utilized in the blending frameworks of sound and music equalizer.

  • Mechanical Potentiometer:

There are various types of potentiometers accessible on the lookout, in that mechanical kinds are utilized for controlling physically to change the obstruction just as the yield of the gadget. Notwithstanding, a computerized potentiometer is utilized to change its opposition naturally dependent on the given state. This sort of potentiometer works precisely like a potentiometer and its obstruction can be changed through advanced correspondence, for example, SPI, I2C as opposed to turning the handle straightforwardly.  

These potentiometers are called POT because of their POT moulded design. It incorporates three terminals like I/p, o/p, and GND alongside a handle on its zenith. This handle works like control to control the opposition by pivoting it in the two ways like clockwise in any case anticlockwise.  

The fundamental downside of computerized potentiometers is that they are basically impacted by various natural factors like soil, dust, dampness, and so on To conquer these drawbacks, advanced Potentiometers (digiPOT) were executed. These potentiometers can work in conditions like residue, soil, dampness without changing their activity.

  • Digital Potentiometer:

Advanced potentiometers are likewise called as digiPOTs or variable resistors which are utilized to control simple signs utilizing microcontrollers. These sorts of potentiometers give an o/p opposition that is alterable relying upon advanced data sources. Some of the time, these are likewise called RDACs (resistive advanced to-simple converters). The controlling of this digit should be possible by advanced signals as opposed to through mechanical development.  



Each progression on the resistor stepping stool incorporates one switch which is associated with the o/p terminal of the advanced potentiometer. The proportion of the obstruction in the potentiometer is not set in stone through the picked venture over the stepping stool. By and large, these means are shown with a bit esteem, for example. 8-pieces are equivalent to 256 stages.  

This potentiometer uses advanced conventions, for example, I²C in any case SPI Bus (Serial Peripheral Interface) for flagging. The greater part of these potentiometers uses basically unstable memory so they didn’t recall their place whenever they are shut down and their last spot might be put away through the FPGA or microcontroller to which they are associated.

Characteristics of a Potentiometer

The attributes of a potentiometer incorporate the accompanying.  

  • It is amazingly exact as it chips away at the assessing strategy instead of the procedure of redirection to decide the unidentified voltages.
  • It decides the equilibrium point in any case invalid which needn’t bother with power for the measurement.
  • The potentiometer working is liberated from the obstruction of source as there is no progression of current all through the potentiometer as it is adjusted.
  • The primary attributes of this potentiometer are the goal, tighten, the checking codes and bounce on/jump off opposition

Potentiometer Sensitivity

The potentiometer affectability can be characterized as the most un-potential variety that is determined with the assistance of a potentiometer. Its affectability chiefly relies on the potential slope esteem (K). At the point when the potential slope esteem is low, the potential distinction that a potentiometer can ascertain is more modest, and afterwards, the potentiometer affectability is more.  

In this way, for a given likely divergence, the potentiometer affectability can increment through the increment in the potentiometer’s length. The potentiometer affectability can likewise be expanded for the accompanying reasons.  

  • By expanding the potentiometer length
  • By diminished the progression of current inside the circuit through a rheostat
  • The two procedures will help with diminishing the worth of the expected inclination and expanding the resistivity.

Measurement of Voltage by Potentiometer

The estimation of voltage should be possible utilizing a potentiometer in a circuit is an exceptionally basic idea. In the circuit, the rheostat should be changed and the current move through the resistor can be changed so that for every unit length of the resistor, a definite voltage can be dropped.  

Presently we need to fix one completion of the branch to the resistor starting though the opposite end can be associated toward the resistor’s sliding contact utilizing a galvanometer. Thus, presently we need to move the sliding contact over the resistor till the galvanometer shows zero diversion. When the galvanometer arrives at its zero states then we need to take note of the position perusing on the resistor scale and in view of that, we can find the voltage in the circuit. For better arrangement, we can change the voltage for every unit length of the resistor.

Applications of Potentiometers

Potentiometers are used in a variety of applications.



  • Potentiometer as a Voltage Divider:

A set input voltage applied across the two ends of the potentiometer can be used as a voltage divider to create a manually adjustable output voltage at the slider. The load voltage across RL may now be calculated as follows:

VL= R2RL. VS/(R1RL + R2RL + R1R2)

  • Audio Control:

Audio control devices, such as sliding potentiometers, are one of the most popular uses for contemporary low-power potentiometers. Sliding potentiometers (faders) and rotating potentiometers (knobs) are commonly used for frequency attenuation, volume adjustment, and other audio signal features.

  • Television:

Picture brightness, contrast, and colour response were all controlled via potentiometers. The “vertical hold,” which impacted the synchronisation between the received picture signal and the receiver’s internal sweep circuit, was often adjusted with a potentiometer (a multi-vibrator).

  • Transducers:

Perhaps the most well-known application is estimating removal. To quantify the dislodging of the body, which is portable, is associated with the sliding component situated on the potentiometer. As the body moves, the situation of the slider additionally changes likewise so the opposition between the proper point and the slider changes. Because of this the voltage across these focuses additionally changes.  

The adjustment of obstruction or the voltage is corresponding to the adjustment of the removal of the body. Accordingly, the voltage change shows the removal of the body. This can be utilized for the estimation of translational just as rotational dislodging. Since these potentiometers work on the guideline of opposition, they are additionally called resistive potentiometers. For instance, the shaft revolution may address a point, and the voltage division proportion can be made corresponding to the cosine of the point.

Advantages of Potentiometer

The upsides of the potentiometer incorporate the accompanying.  

  • There is no possibility of getting mistakes since it utilizes the zero reflection strategy.
  • The normalization should be possible by utilizing an ordinary cell straightforwardly
  • It is utilized to quantify little emf’s because of exceptionally touchy
  • In view of the prerequisite, the potentiometer length can be expanded to get precision.
  • At the point when the potentiometer is utilized in the circuit for estimation then it doesn’t draw any current.
  • It is utilized to quantify the inward obstruction of a cell just as thinks about the e.m.f. of two cells however by utilizing a voltmeter, it is unimaginable.

Disadvantages of Potentiometer

The disservices of the potentiometer incorporate the accompanying.  



  • The potentiometer use isn’t advantageous
  • The cross-segment space of the potentiometer wire ought to be reliable so that is absurd basically.
  • While doing a trial, the wire temperature ought to be steady yet this is hard because of the current stream.
  • The primary downside of this is, it needs colossal power to move its wiper or sliding contacts. There is disintegration due to the development of the wiper. So it diminishes the transducer’s life
  • Data transfer capacity is restricted.

Sample Questions 

Question 1: What is the concept behind a potentiometer?

Answer:

The potentiometer operates on the concept that the potential difference between any two locations on a uniform current carrying conductor is proportional to the distance between them.

Question 2:  The resistivity of a potentiometer wire is given as 5 x 10-6 Ωm. The area of cross-section of the wire is given as 6 x 10-4 m2. Find the potential gradient if a current of 1 A is flowing through the wire.

Answer:

 K = V/L

= IR/L

= (IρL/A)/L

= Iρ/A

Substituting the values we get K =1x 5 x 10-6/6 x 10-4 m2 = 0.83 x 10-2 v/m

Question 3: What are the advantages of the Potentiometer?

Answer:

The upsides of potentiometer incorporate the accompanying.  

  1. There is no possibility of getting mistakes since it utilizes the zero reflection strategy.
  2. The normalization should be possible by utilizing an ordinary cell straightforwardly
  3. It is utilized to quantify little emf’s because of exceptionally touchy
  4. In view of the prerequisite, the potentiometer length can be expanded to get precision.
  5. At the point when the potentiometer is utilized in the circuit for estimation then it doesn’t draw any current.
  6. It is utilized to quantify the inward obstruction of a cell just as thinks about the e.m.f. of two cells however by utilizing a voltmeter, it is unimaginable.

Question 4: What is Potentiometer?

Answer:

A potentiometer is an electronic device that measures the EMF (electromotive force) of a cell as well as the cell’s internal resistance. It’s also used to compare the EMFs of various cells. In most applications, it may also be used as a variable resistor. These potentiometers are widely employed in the production of electronics equipment that allows users to alter electrical circuits to achieve the desired outputs. Although its most obvious application must be for volume controls on radios and other audio-related electronic equipment.

Question 7: What are the characteristics of a potentiometer?

Answer:

The attributes of a potentiometer incorporate the accompanying.  

  • It is amazingly exact as it chips away at the assessing strategy instead of the procedure of redirection to decide the unidentified voltages.
  • It decides the equilibrium point in any case invalid which needn’t bother with power for the measurement.
  • The potentiometer working is liberated from the obstruction of source as there is no progression of current all through the potentiometer as it is adjusted.
  • The primary attributes of this potentiometer are goal, tighten, the checking codes and bounce on/jump off opposition



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