What is a potentiometer – Construction, Types, Uses, Working Principle & Applications

Hello readers, welcome to the new post. In this post, we will learn what a entiometer is. The potentiometer is an electronic component used for measuring and controlling the resistance of the circuit. In this post we will learn different parameters about potentiometers, such as construction, types, uses, working principles, and applications. So let’s get started. What is a potentiometer? 

What is a potentiometer?

• The potentiometer is a 3-terminal resistor that comes with a sliding or rotating contact that makes an adjustable voltage divider.
• If two terminals use one end and wiper it works as a variable resistor or rheostat.
• The measuring instruments are known as voltage dividers used for measuring electrical potential; the component is the implementation of the same working.
• A potentiometer is used to control electrical devices like volume controls on audio instruments. It is also used in speed control of fans.
• It operated through processes used as position transducers, such as in the joystick.
• Potentiometers are rarely used for direct control of power, as power dissipated in a potentiometer will be comparable with power in a controlled load.

Construction of a Potentiometer

• The potentiometer is made with the use of a resistive material strip, normally of a carbon mixture. With has a wiper that can be set and placed on a strip.
• Each side strip is connected with a pin. The central pin is connected to the wiper.
• The wiper touches the strip at any point between the two ends. The position of the wiper defines the resistance between the wiper and the side pins. We can move the point where the wiper connects to the carbon strip through the turning shaft of the potentiometer.
• If we move the wiper to the left side, the resistance between the central pin and left pin reduces. And resistance between the central pin and right pin rises.
• If you move the wiper to the right side, a reverse process will occur. When we buy a potentiometer, we have to set a value. Such as 100k. It is the value that we will get if we measure resistance between two endpoints. It is the highest resistance value we can get from a potentiometer.

Types of Potentiometers

The main types of potentiometers are rotary, linear, multi-turn, and digital.

Linear Potentiometer

• This type of potentiometer has a resistive element in a straight line, offering linear changes in resistance. It is used in volume controls, faders, and linear position sensors. This potentiometer is similar, but the difference is that instead of rotary motion, the sliding contact gets moved on the resistor linearly.
• The two ends of the straight resistor are connected with the source voltage. The sliding contact can slide on the resistor through a track connected with a resistor. The terminal connected with sliding is connected to one point of the output circuit, and one with terminals of resistors is connected to the other end of the output circuit.
• This potentiometer is used for measuring voltage about the circuit branch to measure the inner resistance of the battery cell for comparison with the standard cell. It is used in the equalizer of music and sound mixing systems.

Rotary Potentiometer

• It has a resistive element in a circular shape that offers circular changes in resistance. It is mostly used in switches, knobs, and rotary position sensors. Rotary potentiometer used for getting adjustable supply voltage to electronic circuits and electrical circuits. The volume controller of the radio transistor is a common example of a rotary potentiometer where a rotary knob controls supply to the amplifier.
• This potentiometer comes with 2 terminal contacts between which uniform resistance is positioned in a semi-circular pattern. The device also comes with a middle terminal that is connected to resistance through a sliding contact connected with the rotary knob.
• Through a rotating knob, we can move the sliding contact on the semi-circular resistance. The voltage is taken between the resistance end contact and the sliding contact.
• The potentiometer is also called POT. POT is used in substation battery charges for adjusting the charging voltage of the battery. There are many uses of rotary potentiometers where smooth voltage control is needed.

Multi-turn Potentiometer

• The multi-turn pots were made with wipers that operated on a spiral or helical form or through the use of a worm gear. Normally these pots come with many rotations, such as 5, 10, or 20, for high precision.
• These posts are used in trim pots on PCB boards that need high accuracy and resolution.
• Commonly used multi-turn potentiometers are Bourns potentiometers.

Digital Potentiometer

• It is an electronic component that controls the functions of a mechanical potentiometer. It comes with a set of resistive elements and switches that are used to regulate it in digital form.
• It is used in audio and video instruments and industrial control systems.
• The digital potentiometer is a 3-terminal instrument with two fixed-end terminals and one wiper terminal that is used for changing output voltage.
• Digital potentiometers come with different uses, such as celebrating systems, adjusting offset voltage, tuning filters, controlling screen brightness, and controlling sound volume.
• The mechanical potentiometer has many disadvantages that make it not useful for uses where accuracy is needed.
• Size, wiper contamination, mechanical wear, and resistance drift humidity are some disadvantages of a mechanical potentiometer. To minimize these disadvantages, a digital potentiometer is the best to house, as it has high accuracy.

Advantages of Digital Potentiometers

• It offers reliable operation.
• It has high accuracy.
• It is small in size; multiple potentiometers can be configured on one chip.
• It has very little resistance drift.
• It does not have a moving part.
• It has less effect on environmental conditions such as vibrations, humidity, shocks, and wiper contamination.
• Its tolerance is ±1%.
• Its dissipation power is low, about tens of milliwatts.

Disadvantages of Digital Potentiometers

• It is not best for high-temperature conditions and high-power uses.
• Due to the parasitic capacitance of electronic switches, there are bandwidth factors that are in digital potentiometers. That is the highest signal frequency that can cross-resistance terminals with less than 3 dB attenuation in the wiper. The transfer equation is like a low-pass filter.
• The nonlinearity in wiper resistance added harmonic distortion to the output signal. The total harmonic distortion, or THD, defines the degree to which the signal is degraded after crossing the resistance.

Potentiometer Driver Cell

Potentiometers measure voltage by comparing measuring voltage with voltage about the resistance of the potentiometer. For the operation of a potentiometer, there should be a voltage source connected to the potentiometer circuit. This cell offers a voltage source to drive a potentiometer called a driver cell.

The driver cell provides current through the resistance of the potentiometer. The multiple of current and resistance of the potentiometer offers full-scale voltage of the device. By adjusting this voltage, we can vary the sensitivity of the potentiometer.

It is normally done by adjusting the current through resistance. The current passing through the resistance is regulated by the rheostat connected in series with the driver cell. So it is known that the voltage of the driver cell should be higher than the voltage measured.

How to Select a Potentiometer?

• The selection of an accurate potentiometer for certain use and installation conditions is important.
• Factors that must be considered are installation point, required size, and connection type.
• Not all features affect the device’s electrical parameters, but still, be carefully considered to make sure that the pot can easily be accessed and set when required.
• Another parameter that must be noted is the type of adjustment process. With mechanical models, it can be selected between slid or rotary knobs. In some applications, the use of a certain type or design can increase usability.