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Potentiometer (POT) Symbol, Principle, Type And Application Characteristics

Potentiometer (POT) Symbol, Principle, Type And Application Characteristics

November 29 , 2023 0

A potentiometer, or POT, is a three-terminal device that manually adjusts resistance using removable contacts. As we all know, resistors are simple electrical devices that resist the flow of current in a circuit. Ordinary resistors usually have a fixed resistance. But what if you want to change the resistance according to the needs of your application? This is where the potentiometer comes into play.

Potentiometer Symbol And StructureSince

the potentiometer is essentially a resistor, but a variable resistor, the symbol of the potentiometer is also close to the symbol of the resistor, and the following figure shows the symbol of the potentiometer.

This symbol represents resistors with terminals 1 and 3 and sliding contact terminals 2. Taking a look at the structure of a typical potentiometer should give you a better understanding of this. In a rotary contact type potentiometer, there is a resistance track connected between terminals 1 and 3. A sliding contact, also known as a Wiper, will move end-to-end along the resistance track to change the resistance.

The pins of the Trimpot potentiometer include Pin1 (Fixed End), Pin2 (Variable End), and Pin3 (Fixed End), where:

Pin1 (Fixed End) : The connection of fixed end 1 can be connected to one end of the resistance path

Pin2 (Variable End) : The connection of the variable end 2 can be done by connecting it to the wiper

Pin3 (Fixed End) : The connection of the fixed end 3 can be made by connecting it to the other end of the resistance path

Potentiometer AS A Rheostat

A potentiometer can be used as a rheostat by using only two of its terminals: one is the wiper and the other is one of the two external terminals. In this case, the potentiometer acts as a variable resistor at both ends, increasing or decreasing the resistance value by turning the wiper.

Potentiometer AS Voltage Divider

Another useful application of a potentiometer is that it can be used as a voltage divider, and as we all know, the voltage divider circuit consists of two resistors in series. A voltage is applied to the end of the resistor and the output voltage is obtained at both ends of the resistor.
This simple circuit is used to convert high voltage to low voltage. With the help of a potentiometer, a similar voltage divider can be built using all three terminals.

The input voltage is applied between the two external terminals of the potentiometer, and the output voltage is obtained between the tap and the external terminal connected to the GND of the input power supply. As potentiometer allows change
Variable resistance, so you can basically change the output voltage of the divider. Therefore, it is a voltage divider with variable output voltage.

Structure And Working Principle OF Potentiometer

The potentiometer consists of a long resistance line L and a known EMF V cell made of Kang, this voltage is called the driver battery voltage. Connect both ends of the resistance wire L to the battery terminals as shown in the figure below, assuming this is a primary circuit arrangement.
One of the terminals of the other battery (whose EMF E is to be measured) is located at one end of the primary circuit, and the other end of the battery terminal is connected via the galvanometer G to any point on the resistance line. Now assume that this arrangement is a secondary circuit. The arrangement of potentiometers is shown in the figure below.

Its basic working principle is based on the process that the potential drop in any part of the wire is proportional to the length of the wire, provided, of course, that the wire has a uniform cross-sectional area and a constant current flowing through it."When there is no potential difference between any two nodes, there will be a current flow." Now the potentiometer wire is actually A high resistivity (p) wire with a uniform cross-sectional area A.

Therefore, it has a uniform resistance throughout the wire.

Now this potentiometer terminal is connected to a high EMF V unit called a driver unit or voltage source (ignoring its internal resistance). Let the current through the potentiometer be 1, R is the total resistance of the potentiometer, and then by Ohm's law V=IR, there is:R=pL/A, so V= IpL/ABecause 0 and A are always constant, current 1 remains constant through a rheostat.So Lp/A=K (constant)So V is equal to KL.

Now suppose you put a unit E with an EMF lower than the drive unit into the circuit, as shown in the figure above.

Assuming it has EMF E, it has:E = Lx / A =在When this cell is placed in the circuit shown in the figure above and a galvanometer is connected at the corresponding length (x), no current will flow through the galvanometer because the potential difference is equal to 0.So the galvanometer G test shows zero. Then the length (x) is called the length of zero. Now by knowing the constant K and the length x, we can find the unknown EMFE = Lox / A =在Second, you can also compare the EMF of the two cells, so that the first cell of EMF E1 gives a zero at length =L1, and the second cell of EMF E2 shows a zero at length =L2, then:E1 and E2 = L1 / L2

Common Types OF Potentiometers

The most common form of potentiometer is a single rotating potentiometer, and this type of potentiometer is commonly used for audio volume control (logarithmic dimension) as well as many other applications. Different materials are used to build potentiometers, including carbon components, cermets, conductive plastics, and metal films.

Rotate The Potentiometer

These are the most common types of potentiometers in which the cursor moves along a circular path. These potentiometers are primarily used to provide variable voltage to a small portion of the circuit. The best example of such a rotating potentiometer is the volume controller of a radio transistor, where the knob controls the current flowing to the amplifier.
This potentiometer includes two terminal contacts to position a consistent resistance in a semi-circular model. It also includes an intermediate terminal that is connected to the resistor using a sliding contact connected by a knob. The sliding contact can be turned by turning the knob onto the semicircular resistor. This voltage can be obtained between the resistance and the sliding contact. These potentiometers are used where level voltage control is required.

Linear Potentiometer

In these types of potentiometers, the cursor moves along a linear path. Also known as trickle block, wedge block or fader. The potentiometer is similar to the rotating type, but in this potentiometer, the sliding contact simply rotates linearly on the resistor. The connection between the two ends of the resistor straddles the voltage source. Sliding contacts on the resistor can be moved using a path connected through the resistor.
The terminal of the resistor is connected to the trickling end, the sliding end is connected to one end of the circuit output, and the other end is connected to the other end of the circuit output. This potentiometer is mostly used to calculate the voltage in the circuit, to measure the internal resistance of the cell, and is also used in the hybrid system of sound and music equalizer.

Mechanical Potentiometer

There are different kinds of potential dew on the market, where the mechanical type is used for manual control to change the resistance as well as the output of the device. However, a digital potentiometer is used to automatically change its resistance according to a given state. This potentiometer works as accurately as a potentiometer, and its resistance value can be changed by digital communication such as SP1, 12C, rather than directly turning the knob.

Digital Potentiometer

Digital potentiometers, also known as digital potentiometers or variable resistors, are used to control analog signals using microcontrollers. The 0/p resistance provided by these types of potentiometers can be changed depending on the digital input. Sometimes, these are also called RDacs (resistive digital-to-analog converters). The control of this digital potentiometer can be done by digital signals rather than by mechanical motion.
Each step on the resistance ladder includes a switch that is connected to the /p terminal of the digital potentiometer. The resistance ratio in the potentiometer can be determined by the step size selected on the ladder
Digital potentiometers are not affected by environmental factors and can work in dust, dirt, moisture and other environments without changing their operation.

Main Features OF Potentiometer

Potentiometer features include the following:
Very accurate, as it uses evaluation techniques rather than deflection techniques to determine unidentified voltages. Operation is not affected by the source resistance because no current flows in the potentiometer because it is balanced. The main features of the potentiometer are resolution, taper, marking code and pull-up/pull-down resistance

Potentiometer Sensitivity

Potentiometer sensitivity can be defined as the minimum potential change calculated with the help of a potentiometer. Its sensitivity depends mainly on the potential gradient value (K). When the potential gradient value is low, the smaller the potential difference that the potentiometer can calculate, the higher the sensitivity of the potentiometer.
Therefore, for a given potential difference, the sensitivity of the potentiometer can be increased by increasing the length of the potentiometer. Potentiometer sensitivity can also be improved for the following reasons.
By increasing the potentiometer length
Reduce the current in the circuit by means of a rheostat.
Both techniques will help reduce the value of the potential gradient and increase the resistivity of

Potentiometer Advantages And Disadvantages

The advantages of potentiometers include the following:
. This is not easy because it uses the zero reflection method
Standardization can be done by using normal units directly.
Because of its high sensitivity, it is used to measure small electromotive forces.
As needed, the length of the potentiometer can be increased to obtain accuracy.
When a potentiometer is used to make a measurement in a circuit, it does not absorb any current.
. It is used to measure the internal resistance of the battery and compare the electromotive force of the two batteries, but this is not possible with a voltmeter.
The disadvantages of potentiometer include the following aspects:
The potentiometer is not convenient to use
The cross-sectional area of the potentiometer line should be consistent, which is impossible in practice.
When doing the experiment, the wire temperature should be stable, but due to the current flow, but this is difficult
Bandwidth is limited.

Potentiometer Application

Potentiometer applications include the following.
Potentiometer as voltage divider; The potentiometer can be used as a voltage divider to obtain a manually adjustable output voltage at the slider from a fixed input voltage applied at both ends of the potentiometer.
2, audio control, sliding potentiometer is one of the most common uses of modern low-power potentiometer, used as audio control equipment. Both sliding potentiometers (faders) and rotating potentiometers (knobs) are often used to attenuate frequencies, adjust loudness and different characteristics of audio signals.
3, TV, potentiometer is used to control screen brightness, contrast and color response. Potentiometers are often used to tune "vertical hold", which affects the synchronization between the received image signal and the receiver's internal scanning circuit (the multivibrator).
One of the most common applications of sensors is to measure displacement. To measure the displacement of a movable body, a sliding element located on the potentiometer is connected. As the body moves, the position of the slider changes, so the resistance between the fixed point and the slider changes, and so does the voltage at these points. The change in resistance or voltage is proportional to the change in the displacement of the object. So the voltage change represents the displacement of the object. This can be used to measure translational and rotational displacement. Since these potentiometers work according to the principle of resistance, they are also called resistive potentiometers. For example, the rotation of an axis can represent an Angle, and the partial pressure ratio can be made proportional to the cosine of the Angle.

Sum Up

The above is about the potentiometer pin arrangement structure, type, characteristics, heterotropy, advantages, disadvantages and application of the relevant knowledge introduction, hope to help everyone to have a better understanding of the potentiometer.