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CatalogⅠ What Is a Potentiometer?Ⅱ How Does a Potentiometer Work?Ⅲ Types of Potentiometers3.1 Manually adjustable potentiometers3.2 Digital potentiometersⅣ Basic Electrical Characteristics of PotentiometersⅤ Advantages and Disadvantages of Potentiometer5.1 Advantages of Digital Potentiometers5.2 Disadvantages of Digital PotentiometersⅥ Applications of Potentiometer6.1 Audio control6.2 Television6.3 Motion control6.4 Transducers6.5 Computation Ⅶ How to Wire a Potentiometer?7.1 Part 1: Selecting and Preparing a Pot7.2 Part 2: Soldering the Terminals7.3 Part 3: Using Your PotentiometerⅧ Rheostat VS PotentiometerⅨ ConclusionⅩ Frequently Asked Questions about PotentiometerⅠ What Is a Potentiometer?A potentiometer is a three-terminal resistor with a sliding or revolving contact that serves as a voltage divider that may be adjusted. When only one terminal, one end, and the wiper, are employed, it operates as a variable resistor or rheostat. The term "potentiometer" is derived from the phrases Potential Difference and Metering and dates back to the early days of electrical research. It was considered at the time that altering huge wire-wound resistive coils metered or measured a specific amount of potential difference, so making it a type of voltage-metering device. Basic Information of Potentiometer A potentiometer is also known as a pot or potentiometer. The single-turn rotary potentiometer is the most common type of potentiometer. This sort of pot is commonly employed in audio volume control (logarithmic taper) and a variety of other applications. Potentiometers are made from a variety of materials, including carbon composition, cermet, wire-wound, conductive plastic, and metal film. Potentiometers are often used to control electrical devices such as audio volume controls. Potentiometers with a machine can be used as position transducers, such as in a joystick. Potentiometers are rarely used to regulate considerable power (greater than a watt) directly since the power dissipated in the potentiometer is comparable to the power in the controlled load. Ⅱ How Does a Potentiometer Work?How Potentiometer Works A potentiometer is a type of electronic component that is not active. Potentiometers function by changing the location of a sliding contact across a uniform resistance. The full input voltage is applied over the entire length of the resistor in a potentiometer, and the output voltage is the voltage drop between the fixed and sliding contacts, as shown below.  The two terminals of the input source are fixed to the end of the resistor in a potentiometer. To change the output voltage, move the sliding contact along with the resistor on the output side.This differs from a rheostat in that one end is fixed and the sliding terminal is linked to the circuit, as illustrated below.  This is a simple device for comparing the emf of two cells as well as calibrating ammeters, voltmeters, and wattmeters. A potentiometer's basic operation is straightforward. Assume we have two batteries connected in parallel via a galvanometer. As indicated in the picture below, the negative battery terminals are connected together, and the positive battery terminals are likewise connected together via a galvanometer. If the electric potential of both battery cells is the same, there is no circulating current in the circuit, and the galvanometer shows no deflection. The operation of a potentiometer is dependent on this phenomenon. Consider another circuit in which a battery is linked across a resistor using a switch and a rheostat, as shown in the diagram below. Throughout its length, the resistor has the same electrical resistance per unit length. As a result, the voltage drop per unit length of the resistor is constant along its length. Assume that by adjusting the rheostat, we get a volt voltage drop per unit length of the resistor. Now, connect the positive terminal of a standard cell to point A on the resistor, and the negative terminal to a galvanometer. As indicated in the image above, the other end of the galvanometer is in touch with the resistor through a sliding contact. By adjusting this sliding end, a point like B is discovered where there is no current flowing through the galvanometer and thus no deflection in the galvanometer. That is, the voltage appearing in the resistor across points A and B just balances the emf of the standard cell. If the distance between locations A and B is L, then the emf of a standard cell E = Lv volt can be written. This is how a potentiometer monitors the voltage between two locations (in this case, A and B) without introducing any current into the circuit. A potentiometer's specialty is that it can measure voltage with extreme precision. Ⅲ Types of Potentiometers3.1 Manually adjustable potentiometersPotentiometers come in a wide range of shapes and sizes. Manually adjusted potentiometers are classified as having either rotary or linear movement. The available types and their applications are listed in the tables below. In addition to manually adjustable pots, electronically controlled potentiometers, sometimes known as digital potentiometers, are available. Rotary potentiometersThe most common type of potentiometer, with the wiper moving in a circular motion. TypeDescriptionApplicationsSingle-turn potA single rotation of approximately 270 degrees or 3/4 of a full turn.The most common pot is used in applications where a single turn provides enough control resolution.Multi-turn potMultiple rotations (mostly 5, 10, or 20), for increased precision. They are constructed either with a wiper that follows a spiral or helix form or by using a worm gear.Used where high precision and resolution are required. The worm-gear multi-turn pots are often used as trim pots on PCB.Dual-gang potTwo potentiometers combined on the same shaft, enabling the parallel setting of two channels. Most common are single-turn potentiometers with equal resistance and taper. More than two gangs are possible but not very common.Used in for example stereo audio volume control or other applications where 2 channels have to be adjusted in parallel.Concentric potDual potmeter, where the two potentiometers are individually adjusted by means of concentric shafts. Enables the use of two controls on one unit.Often encountered in (older) car radios, where the volume and tone controls are combined.Servo potA motorized potmeter can also be automatically adjusted by a servo motor.Used where manual and automatic adjustment is required. Often seen in audio equipment, where the remote control can turn the volume control knob. Linear potentiometersPotentiometers that allow the wiper to move in a straight line. Also referred to as a slider, slide pot, or fader. TypeDescriptionApplicationsSlide potSingle linear slider potentiometer, for audio applications also known as a fader. High-quality faders are often constructed from conductive plastic.For single-channel control or measurement of distance.Dual-slide potDual slide potentiometer, single slider controlling two potentiometers in parallel.Often used for stereo control in professional audio or other applications where dual parallel channels are controlled.Multi-turn slideConstructed from a spindle that actuates a linear potentiometer wiper. Multiple rotations (mostly 5, 10, or 20), for increased precision.Used where high precision and resolution are required. The multi-turn linear pots are used as trim pots on PCB but are not as common as the worm-gear trimmer potentiometer.Motorized faderFader which can be automatically adjusted by a servo motor.Used where manual and automatic adjustment is required. Common in-studio audio mixers, where the servo faders can be automatically moved to a saved configuration.3.2 Digital potentiometersPotentiometers that be operated electronically are known as digital potentiometers. In most situations, they consist of a sequence of small resistive components. Every resistive element has a switch that can be used as the tap-off point or virtual wiper position. Digital potentiometers can be controlled by up/down signals or protocols such as I2C and SPI. Ⅳ Basic Electrical Characteristics of PotentiometersNominal Total Resistance (Total Resistance)The nominal total resistance is the resistance value that represents the standard value for a potentiometer.Total resistance is defined as the resistance between terminals 1 and 3. Residual ResistanceResidual resistance is the resistance between terminals 1 and 2 when the wiper is positioned at the terminal 1 end or the resistance between terminals 3 and 2 when the wiper is positioned at the terminal 3 ends. The minimum resistance value while the wiper is at its minimum or maximum range of movement is referred to as residual resistance.Residual Resistance Maximum AttenuationWhen the output is at its lowest, the output voltage ratio (in decibels) is the highest. It denotes the extent to which audio equipment's volume can be reduced. Maximum attenuation and insertion loss (see below) are employed instead of residual resistance in the context of potentiometers for volume control. Maximum Attenuation Insertion LossWhen the output is at its maximum, the output voltage ratio (in decibels) is the highest. It denotes the extent to which audio equipment's volume may reach full strength. In the context of volume control potentiometers, insertion loss and maximum attenuation (see below) are employed in place of residual resistance.Insertion Loss Resistance TaperThe proportion of the output voltage between terminals 1 and 2 (or terminals 2 and 3) with respect to the input voltage between terminals 1 and 3. It varies with wiper location, as illustrated by the resistance taper curves on the right. A choice can be made, for example, between the B curve, which is suitable for level adjustment, and the A curve, which produces a more natural sound to the human ear.Resistance Taper Sliding NoiseThis is the minor electrical noise produced when the wiper passes over the resistive element.The more noise there is, the easier it is for audio equipment volume control to produce an unpleasant crackling sound. Sliding Noise Ⅴ Advantages and Disadvantages of Potentiometer5.1 Advantages of Digital PotentiometersDigital potentiometers provide the following advantages: 1)Higher dependability 2)Increased accuracy 3)Small size, several potentiometers can be packed on a single chip4)Minimal resistance drift5)Impervious to environmental conditions such as vibrations, dampness, shocks, and wiper pollution.6)There is no moving part7)Tolerance of up to 1%8)Very low power dissipation, tens of milliwatts or less 5.2 Disadvantages of Digital Potentiometers1)Digital potentiometers have the following drawbacks: they are not ideal for high-temperature environments or high power applications.2)In digital potentiometers, there is a bandwidth consideration due to the parasitic capacitance of the electronic switches. It is the highest frequency at which a signal can traverse the resistance terminals with less than 3 dB attenuation in the wiper. The transfer equation is analogous to that of a low pass filter.3)The wiper resistance's nonlinearity introduces harmonic distortion onto the output signal. The total harmonic distortion, or THD, measures how much the signal degrades after passing through the resistance. Ⅵ Applications of PotentiometerPotentiometers are rarely used to control considerable quantities of power directly (more than a watt or so). They are instead used to change the level of analog signals (for example, volume controls for audio equipment) and as control inputs for electronic circuits. A light dimmer, for example, employs a potentiometer to regulate the switching of a TRIAC, and so indirectly controls the brightness of lamps. Preset potentiometers are commonly used in electronics to make modifications during manufacture or repair. Potentiometers that are operated by the user are commonly employed as user controls and may control a wide range of equipment functions. Potentiometers were widely used in consumer electronics until the 1990s, when rotary incremental encoders, up/down pushbuttons, and other digital controllers took their place. However, they continue to be used in a variety of applications, including volume controls and position sensors. 6.1 Audio controlLow-power potentiometers, both slide, and rotary are used to control audio equipment by adjusting loudness, frequency attenuation, and other audio signal parameters. The 'log pot,' that is, a potentiometer with a resistance, taper, or "curve" (or law) of a logarithmic (log) form, is employed as the volume control in audio power amplifiers, where it is also known as an "audio taper pot," because the amplitude response of the human ear is roughly logarithmic. It guarantees that, for example, on a volume control marked 0 to 10, a setting of 5 sounds half as loud as a setting of 10. An anti-log pot, also known as a reverse audio taper, is simply the inverse of a logarithmic potentiometer. It is nearly always ganged with a logarithmic potentiometer, for example, in audio balance control. Potentiometers work as tone controllers or equalizers when used with filter networks. Because of the straight-line character of the physical sliding action, the term linear is occasionally used incorrectly in audio systems to describe slide potentiometers. When applied to a potentiometer, whether sliding or rotary, the term linear refers to a linear relationship between the pot's position and the measured value of the pot's tap (wiper or electrical output) pin. 6.2 TelevisionPreviously, potentiometers were employed to regulate picture brightness, contrast, and color response. A potentiometer was frequently used to modify "vertical hold," which affected synchronization between the receiver's internal sweep circuit (sometimes a multivibrator) and the received picture signal, as well as audio-video carrier offset, tuning frequency (for push-button sets), and so on. It also aids in wave frequency modulation. 6.3 Motion controlPotentiometers can be employed as position feedback devices in closed-loop control systems, such as servomechanisms. This motion control method is the most basic means of monitoring angle or displacement. 6.4 TransducersPotentiometers are also extensively utilized as a component of displacement transducers due to their ease of manufacturing and ability to produce a large output signal. 6.5 ComputationHigh precision potentiometers are used in analog computers to scale intermediate results by specified constant factors or to create initial conditions for a calculation. A motor-driven potentiometer can be used as a function generator, with a non-linear resistance card providing trigonometric function approximations. For example, the shaft rotation may indicate an angle, and the voltage division ratio could be proportional to the angle's cosine. Ⅶ How to Wire a Potentiometer?Potentiometers, often known as pots, are a type of resistor that is used to control the output signal of an electronic device such as a guitar, amplifier, or speaker. They have a little shaft on top that acts like a knob; when the user twists the shaft, the resistance on the signal increases or decreases. This change in resistance is then utilized to modulate the loudness, gain, or strength of the electrical signal. To install and wire a pot, ground the first terminal, connect the input signal to the third terminal, and then connect the output signal to the terminal in the middle. To accomplish this, solder each wire to the corresponding terminal. Learn How to Wire a Potentiometer 7.1 Part 1: Selecting and Preparing a PotPlace the pot on a flat surface Step 1: Determine the three major terminals that protrude from the pot's center. Place the pot on a flat surface, three prongs facing you. These are your entry points. The first terminal, or terminal 1, is where you'll find your ground. The pot's input signal is sent to the middle terminal, or terminal 2. The output signal is routed to the third terminal, sometimes known as terminal 3. A tiny ring linked to the second terminal is controlled by the top shaft. You may control how low or high the input is by twisting it. If it helps, think of a potentiometer as a dimmer switch. Terminal 1 serves as the ground, terminal 2 serves as the switch, and terminal 3 serves as the switch turned on. In most cases, a potentiometer is used to throttle an input signal so that it can be changed. At times, a pot can be used to overclock a device with a stronger signal. Look at the resistance numbers Step 2: Examine your pot's resistance numbers to see what range you can reach. Pots are rarely used to control signals higher than a few volts, although the resistance they give is substantial. The wider the range, the more control you have over your gadget. The number on the front of the pot represents the highest amount of resistance of the pot. As a result, a 200K pot can give up to 200,000 ohms of resistance. The 100K potentiometer is the most prevalent variety on the market due to its wide range of audio equipment. These numbers are always printed immediately on a pot. They are often located on the other side of the terminals, immediately next to the shaft. Tip: It is critical to understand how much resistance a pot gives in order to assess whether it is suitable for the task at hand. A 2,000-ohm pot will not provide enough range for a sound system, but it will do for a dimmer switch. Three terminals Step 3: Set your pot on a flat surface with the three terminals facing you. Place your pot on a flat area next to your electronic device. Begin with the placement of the pot if you know where you're going to put it. Turn the three terminals so that they are facing you. Remove any panels on your electrical equipment to expose any backside input or output ports. Place the pot on the uppermost set of rows on a breadboard, terminals facing you. Unplug your electronic gadget before opening any panels or soldering any connections. You don't want to be electrocuted or damage your device forever. Cut 0.5–1 in (1.3–2.5 cm) Step 4: Measure and strip any wires you wish to utilize. You can connect the terminals to the device with any type of soldering wire as long as it is not acid-core. If you have an installation location lined up, measure each length of wire from the termination to the device. Using a cutter, cut any wires to expose the copper. Using the notches on the cutter's blades, cut and remove 0.5–1 in (1.3–2.5 cm) of plastic off the tip of each wire. To get a clean strip, set your wire stripper to match the gauge of the wire. Prepare your work surface with a soldering iron and flux, since you will need to solder your wires. Plumbing makes use of acid-core soldering wire. It is incompatible with your electronics. If the soldering wires do not function, they can be used to wire a certain sort of electronic gadget that requires specialist wiring. 7.2 Part 2: Soldering the TerminalsStep 5: Connect a ground wire from terminal 1 on the left to the chassis. Tap a tiny length of wire with your soldering iron and apply flux to the exposed section. Lower the wire and attach it to the exposed metal section on terminal 1 after it has absorbed some flux. Press your soldering tip against the connector to connect the wire to the terminal. Solder the other end of the cable to your electrical device's exposed, unpainted metal surface. You can utilize terminal 3 on the right if you like, but you must turn the knob clockwise to lessen the signal. Connect your device's output circuit to the middle terminal Step 6: Connect your device's output circuit to the middle terminal.Tin another length of wire in the same way and attach it to the center terminal of the pot. Because this is the point at which the signal enters the pot, it must be linked to the device's output. Solder the wire to the metal connection on the rear of your electronic device's output connection. The input of the potentiometer is linked to the center terminal. That is, the signal leaves the electronic, enters terminal 2, and then leaves terminal 3. As a result, terminal 2 must be linked to the port that outputs the original signal from the device. This would require wiring terminal 2 to a guitar's output jack. This would imply connecting terminal 2 to the integrated audio amplifier's speaker output terminal. Terminal 3 Step 7: Connect terminal 3 to the device's input.Terminal 3 is the potentiometer's output. This is where the pot sends data back to the device. Place a length of exposed soldering wire directly on the terminal. After heating the wire with your soldering pen, connect it to the input port of your electronic device. Look for the exposed metal aperture on the back of the knob or the cable connector at the port's back. Solder the wire straight to the pot to connect it. The signal from your pot exits through Terminal 3, thus it must be wired to the spot where you want to deliver the signal. This would imply connecting terminal 3 to the guitar's input jack. The input channels would be linked to Terminal 3 of an audio amplifier. 7.3 Part 3: Using Your PotentiometerMeasure Potentiometer Step 8: Using a voltmeter, check that your pot is operational.Connect the voltmeter terminals to the input and output terminals of the pot. Turn on the voltmeter and turn the dial to feed a signal. Turn the knob on top of your pot to adjust the signal. If the signal reading on the voltmeter changes as you turn the knob, your potentiometer is working. If the voltmeter registers a signal from your pot yet the gadget does not operate when you turn on your electronics, the soldered connections are faulty. Signal From the Pot Step 9: Turn the shaft to adjust the signal on your device.Turn on your gadget and send a signal to the pot by playing music, striking a guitar note, or turning on a light. Twist the shaft to the left to lessen the volume or brightness. Twist the shaft to the right to enhance the volume or brightness of the light. Switch the shaft to the left to turn off the output. Using your pot, you may now control the amount of resistance that your signal receives. Adjust the Amount of Resistance You can add a knob by sliding it over the potentiometer if you like. You can install a potentiometer with the shaft naked and exposed if you wish. If you want to improve the look of your potentiometer, you may always buy a knob. There are several knobs available on the market that are meant to slide over the shaft of a pot and enhance its appearance. That concludes the steps for wiring a potentiometer. Online electronic stores can tell you what possibilities are available for your specific make and model. Ⅷ Rheostat VS PotentiometerDifferences Between Potentiometers and Rheostats A potentiometer controls the voltage. Variable resistance is provided by a rheostat. A potentiometer has three terminals, whereas a rheostat has two terminals. Both gadgets appear to be similar in construction, yet their operating principles are completely different. Two end terminals of the uniform resistance are linked to the source circuit of the potentiometer. Only one terminal of the uniform resistance is connected to the circuit in a rheostat, leaving the other end of the resistance open. A sliding contact on the resistance is included in both potentiometers and rheostats.rheostat The output voltage of a potentiometer is measured between fixed and sliding contacts. Variable resistance is produced in rheostats by alternating between fixed and sliding terminals. The potentiometer's resistance is connected across the circuit. The rheostat's resistance is linked in series with the circuit. The rheostat is commonly used to manage current by altering resistance via a sliding contact. The voltage of a potentiometer is regulated by moving the sliding contact on the resistance. potentiometer To obtain variable resistance, fixed and sliding terminals are employed. The resistance of the potentiometer is connected across the circuit. The resistance of the rheostat is linked in series to the circuit. A rheostat is a device that controls current by adjusting resistance via a sliding contact. A potentiometer's voltage is controlled by changing the sliding contact on the resistance. Ⅸ ConclusionA potentiometer, also known as a variable resistor, is made up of a resistive track with connections at both ends and a third terminal called the wiper, the position of which divides the resistive track. The wiper's position on the track is mechanically modified by spinning a shaft or using a screwdriver. Variable resistors are classified into two operational modes: variable voltage dividers and variable current rheostats. The potentiometer is a three-terminal device that controls the voltage, whereas the rheostat is a two-terminal device that controls current. This is summarized in the table below: TypePotentiometerRheostatNumber of ConnectionsThree TerminalsTwo TerminalsNumber of TurnsSingle and Multi-turnSingle-turn OnlyConnection TypeConnected Parallel with a Voltage SourceConnected in Series with the LoadQuantity ControlledControls VoltageControls CurrentType of Taper LawLinear and LogarithmicLinear Only The potentiometer, trimmer, and rheostat are electromechanical devices with easily adjustable resistance values. They can be single-turn pots, presets, slider pots, or multi-turn trimmers. Wirewound rheostats are primarily used to regulate electrical current. Potentiometers and rheostats are also available in multi-gang configurations and have either a linear or a logarithmic taper. Potentiometers, on the other hand, may provide highly precise sensing and measurement for linear or rotary movement because their output voltage is proportional to the position of the wipers. Potentiometers have many advantages, including inexpensive cost, simple operation, a wide variety of shapes, sizes, and designs, and the ability to be employed in a wide variety of applications. However, as mechanical devices, they have drawbacks such as eventual wear-out of the sliding contact wiper and/or track, limited current handling capabilities (unlike Rheostats), electrical power constraints, and rotational angles limited to fewer than 270 degrees for single turn pots. Ⅹ Frequently Asked Questions about Potentiometer1. What is a potentiometer used for?A position sensor is a potentiometer. They can measure displacement in any direction. Linear potentiometers measure movement linearly, whereas rotary potentiometers measure rotational displacement. 2. What are the 3 terminals on a potentiometer?There are three pins on a potentiometer. Two terminals (blue and green) are linked to a resistive element, and the third (black) is linked to an adjustable wiper. The potentiometer can function as both a rheostat (variable resistor) and a voltage divider. 3. What is a potentiometer also known as?A potentiometer is a three-terminal variable resistor that may be adjusted manually. A potentiometer is often referred to as a potmeter or pot. The single turn rotary potmeter is the most popular type of potmeter. 4. What is the potentiometer principle?The potential lowered across a segment of a wire of uniform cross-section carrying a constant current is precisely proportional to its length, according to the principle of a potentiometer. A potentiometer is a basic device for measuring electrical potentials (or comparing the e.m.f of a cell). 5. Which wire is used in the potentiometer?Potentiometer wire is typically made of alloys such as constantan or manganin. The temperature coefficient of Constantan or Manganin wire is low. 6. Can I use a potentiometer to control AC motor speed?It is unlikely that you will be able to control the speed of an AC fan with a potentiometer. The technology employed determines whether an AC "mains" fan can be speed adjusted with a pot. Typically, a single-phase induction motor with a capacitor start. 7. What is the null point in a potentiometer?The potentiometer's balancing point, also known as the null point, is the point on the sliding wire where the galvanometer indicates zero deflection. The balance point is discovered in order to ascertain the unknown voltage of the cell connected to the cell. 8. What is the sensitivity of the potentiometer?Potentiometer sensitivity is defined as the smallest potential difference detected with a potentiometer. Potentiometer sensitivity can be enhanced by increasing the length of the potentiometer wire. Using a rheostat to reduce the current in the circuit. 9. What is a potentiometer wire?Potentiometer: A potentiometer is a three-terminal resistor with a sliding or revolving contact that forms an adjustable voltage divider. If only one terminal, one end, and the wiper, are employed, it operates as a variable resistor or rheostat. 10. Why copper wire is not suitable for a potentiometer?Copper wire is not suitable for potentiometers due to its high-temperature coefficient of resistance and low resistivity. As a result, even a small change in temperature might cause a significant change in resistance, changing the experimental conditions. 

CatalogI IntroductionII Definition, Symbol and Labeling of Variable Resistor  2.1 Definition   2.1.1 What is Variable Resistance?   2.1.2 What is Variable Resistor?  2.2 Symbol  2.3 Labeling Method of Variable ResistorIII How The Variable Resistor WorksIV Features of Variable Resistor ShapeV Structure and Function of Variable Resistor  5.1 Basic Structure  5.2 Schematic Diagram of Two Variable Resistors  5.3 The Role of The Variable ResistorVI Types of Variable Resistors  6.1 Resistance box  6.2 Sliding Rheostat  6.3 Potentiometer  6.4 Specific Classification of Variable Resistors   6.4.1 Film Variable Resistor   6.4.2 Wire Wound Variable ResistorVII Typical Application Circuits of Variable Resistor  7.1 Variable Resistor Circuit in Transistor Bias Circuit  7.2 Stereo Balance Control Variable Resistor CircuitVIII Causes and Solutions of Variable Resistor Malfunctions  8.1 Causes of Variable Resistor Malfunctions8.2 Characteristics of Variable Resistor Malfunctions  8.3 Methods For Repairing Variable Resistor  8.4 Testing a Variable Resistor with a Multimeter   8.4.1 Method   8.4.2 PrecautionsIX Active Variable Resistors with Wide Range of Load ImpedanceX One Question Related to Variable Resistors  10.1 Question  10.2 AnswerXI FAQ I IntroductionA resistor is a current-limiting element. After the resistor is connected to the circuit, the resistance of the resistor is fixed. It generally has two pins, which can limit the current flowing through the branch connected to it. Those whose resistance cannot be changed are called fixed resistors, and those with variable resistance are called potentiometers or variable resistors.Setting Up A Variable Resistor, Rheostat, or Fixed ResistorII Definition, Symbol and Labeling of Variable Resistor2.1 Definition2.1.1 What is Variable Resistance?Variable resistance is a kind of resistance, which can play the role of resistance in electronic circuits. The difference from ordinary resistance is its resistance can be continuously changed within a certain range. In some cases where the resistance value is required to change but does not change frequently, a variable resistor can be used. 2.1.2 What is Variable Resistor？A variable resistor is an electronic component with adjustable resistance. It consists of a resistor and a rotating or sliding system. It is usually used in the circuit that needs to adjust the resistance frequently and plays the role of adjusting the voltage, adjusting the current, or controlling the signal. Its main parameters are basically the same as those of the fixed resistor. 2.2 SymbolThe symbol of the variable resistor is R and the unit is Ω. 2.3 Labeling Method of Variable Resistor(1) The variable resistor uses the direct standard method to indicate the nominal resistance value, that is, the nominal resistance value is directly marked on the variable resistor. In the case of high current applications, the variable resistor is also marked with the rated power parameter. In addition, the resistance value of small variable resistors is expressed in three digits, which is the same as that of resistors.(2) For variable resistors used in small-signal circuits, we generally only care about their nominal resistance and have no power requirements. III How The Variable Resistor WorksWhen a voltage is applied between two fixed electric shocks of the resistor body, the position of the contact on the resistor body is changed by rotating or sliding the system, and a position is formed between the movable contact and the fixed contact. Certainly related voltage. In other words, the resistor body of the variable resistor has two fixed ends. By manually adjusting the rotating shaft or sliding handle to change the position of the moving contact on the resistor body, the relationship between the moving contact and any fixed end is changed. The resistance value changes the magnitude of voltage and current. IV Features of Variable Resistor Shape(1) The volume of the variable resistor is larger than that of the general resistor, and at the same time, the variable resistor in the circuit is less, and it can be easily found in the circuit board.(2) There are three pins in the variable resistor, and they are different from each other. One is a moving pin and the other two are fixed. Generally, the two fixed pins can be used interchangeably, but the fixed and moving pins cannot be used interchangeably.(3) There is an adjustment port on the variable resistor. Use a flat-blade screwdriver to protrude into this adjustment port. Turn the screwdriver to change the position of the moving plate and adjust the resistance value.(4) The nominal resistance value can be seen on the variable resistor. This nominal resistance value refers to the resistance value between two fixed chip pins and is also a fixed chip pin and a moving chip pin. The maximum resistance value between.(5) The vertical variable resistor is mainly used in small-signal circuits. Its three pins are vertically downward and mounted vertically on the circuit board. The resistance adjustment port is in the horizontal direction.(6) Horizontal variable resistors are also used in small-signal circuits. Its three pins are at 90 ° to the resistance plane and are mounted vertically on the circuit board with the resistance adjustment port facing upward.(7) The variable resistance of the small plastic case is smaller and has a circular structure. Its three pins are down and the resistance adjustment port is up.(8) Variable resistors (wire-wound structure) for large power applications. The volume is large, and the moving blade can slide left and right to adjust the resistance. V Structure and Function of Variable Resistor5.1 Basic StructureThe variable resistor is chiefly composed of a moving piece, a carbon film body, and three pins. The three pins are two fixed pins (also called fixed pieces) and one moving piece pin. The moving piece of the variable resistor can be rotated left and right. When using a flat-blade screwdriver to reach into the adjustment port and rotate, the contacts on the moving piece can slide on the resistance piece. According to diverse uses, the resistance material of the variable resistor includes metal wire, metal sheet, carbon film, or conductive liquid. For currents of general magnitude, metal-type variable resistors are frequently used. When the current is slight, it is better to use a carbon film type. When the current is large, the electrolytic type is most suitable. 5.2 Schematic Diagram of Two Variable Resistors Figure3. Schematic Diagram of Two Variable Resistors5.3 The Role of The Variable Resistor(1) A variable resistor is an adjustable electronic component, which is composed of a resistor body and a sliding system. The variable resistor resistance is a resistor that can be adjusted for the current or change of the circuit In the case of circuit resistance, the light can be dimmed, and the motor can be controlled to start its speed. (2) The variable resistor mainly controls the current in the series circuit by changing its own resistance, thereby protecting some electrical components with requirements for the current. The variable resistor is generally used in circuits that do not require frequent adjustment, mainly To fix the same value for the resistor. VI Types of Variable Resistors6.1 Resistance BoxVariable resistors are divided into three types: resistance box, sliding rheostat, and potentiometer. The resistance box is a variable resistance device that uses a conversion device to change its resistance value. This conversion device usually adopts a decimal disc type (knob type) structure, and can also adopt a plug type and an end button type structure as required. The circuit of the resistance box can be divided into series lines and series-parallel lines. Compared with the sliding rheostat, the resistance box can continuously change the resistance in the connected circuit, while the sliding rheostat cannot display the resistance value of the connected circuit.Figure4. Resistance Box6.2 Sliding RheostatA sliding varistor is one of the commonly used devices in electricity. Its working principle is to change the resistance by changing the length of the resistance line in the circuit, thereby gradually changing the current in the circuit. The resistance wire of a sliding rheostat is generally a nickel-chromium alloy with a high melting point and a large resistance, and a metal rod is generally metal with low resistance. As a result, when the cross-sectional area of the resistor is constant, the longer the resistance wire, the greater the resistance; the shorter the resistance wire, the smaller the resistance.Figure5. Sliding Rheostat6.3 PotentiometerA potentiometer is a resistance element with three lead-out terminals whose resistance can be adjusted according to certain change law. A potentiometer usually consists of a resistor and a movable brush. When the brush moves along the resistor body, a resistance value or voltage having a certain relationship with the amount of displacement is obtained at the output end. The potentiometer can be used as a three-terminal element or a two-terminal element. The latter can be regarded as a variable resistor. Because its role in the circuit is to obtain an output voltage that has a certain relationship with the input voltage (external voltage), it is called a potentiometer.Figure6. Potentiometer6.4 Specific Classification of Variable ResistorsThe variable resistor can be divided into the film-type variable resistor and wire-wound variable resistor according to the material. 6.4.1 Film Variable ResistorMembrane variable resistors are usually composed of a resistor body (synthetic carbon film), a movable contact (a movable metal reed or a carbon contact), an adjustment part, and three pins (or solder pads). Two of the fixed pins are connected to both ends of the resistor body, and the other pin (center tap) is connected to the movable contact piece. You can change the resistance between the center tap and the two fixed pins by turning the adjustment part with a small flat-blade screwdriver and changing the contact position of the movable contact with the resistor. Membrane variable resistors are available in hermetic, semi-hermetic, and non-hermetic configurations. (1) Fully sealed film variable resistors are also called solid variable resistors. The resistor is made of carbon black, quartz powder, an organic binder and other materials, and then pressed into plastic or epoxy resin. The matrix of the material is polymerized by heating. The movable contacts use carbon contacts and the adjustment parts are made of plastic. The resistor body and the movable contact are sealed by a metal casing (there is an adjustment hole above the metal casing). Its advantage is that it has good dustproof performance and rarely has bad contact failure. (2) The manufacturing process of the resistor body of the semi-sealed film variable resistor and the resistor body of the fully sealed variable resistor is basically the same. The movable contact piece adopts a metal reed, and the outer plastic cover is sealed. When the plastic cover is rotated, the movable contact piece also rotates with it. This variable resistor is easy to adjust, but its dust resistance is not as good as a fully sealed film-type variable resistor. (3) Unsealed film variable resistors are also called chip tunable resistors. The resistor body is made of carbon black, graphite, quartz powder, an organic binder, etc. to form a suspension, which is coated on a glass fiberboard or glue. Made from wooden boards. The movable contact piece uses a metal reed, and the reed has an adjustment hole, and no separate adjustment component is provided. Its disadvantages are poor dust-proof performance, the contacts are susceptible to oxidation, and prone to failure due to poor contact with the synthetic carbon film. 6.4.2 Wire Wound Variable Resistor(1) High-power wire-wound varistor is also called sliding wire varistor, which is divided into axial ceramic tube-type wire-wound variable resistor and porcelain disc-type wire-wound variable resistor. It adopts an unsealed structure.(2) Low-power wire-wound variable resistors include round vertical wire-wound variable resistors, round horizontal wire-wound variable resistors, and square wire-wound variable resistors, all of which are fully sealed. Package structure.In addition, the variable resistor can be divided into a vertical variable resistor and a horizontal variable resistor according to the structure.Figure7. Wire Wound Variable ResistorVII Typical Application Circuits of Variable Resistor7.1 Variable Resistor Circuit in Transistor Bias CircuitThe figure below shows a variable-resistor voltage-dividing bias circuit. In the circuit, the transistor VT1 constitutes a high-frequency amplifier, and RP1, R1, and R2 constitute a voltage-dividing bias circuit. The output voltage of the voltage dividing circuit is determined by the resistance of three resistors, RP1, Rl, and R2. R1 and R2 are fixed resistors. The variable resistor RP1 is adjusted, and then the VT1 static operating current is adjusted. The amount of current determines whether VT1 can work in the best state. Figure8. Variable Resistance Voltage Divider Bias Circuit7.2 Stereo Balance Control Variable Resistor CircuitThe following figure shows the left and right channel gain balance adjustment circuits in the audio amplifier. RP1 in the circuit is a variable resistor in series with R1. Figure9. Left and Right Channel Gain Balance Adjustment Circuit in Audio AmplifierIn the audio circuit, for a two-channel amplifier, we need to strictly require that the left and right channel amplifiers have an equal gain (balanced), but the discreteness of the circuit components makes this impossible. In order to ensure that the gains of the left and right channel amplifiers are equal, left and right channel gain balance adjustment circuit needs to be provided, which is referred to as a stereo balance circuit. In the right channel circuit, the resistance of R2 is determined, so that the gain of the right channel amplifier is fixed. Taking the gain of the right channel amplifier as a reference, changing the resistance of RP1 so that the gain of the left channel amplifier is equal to the gain of the right channel amplifier can achieve the same gain of the left and right channel amplifiers. VIII Causes and Solutions of Variable Resistor Malfunctions8.1 Causes of Variable Resistor Malfunctions(1) The use time is long, causing oxidation.(2) The failure of the circuit caused the variable resistor to overcurrent and burned the carbon film. At this time, the burned trace of the variable resistor can also be seen from the appearance. 8.2 Characteristics of Variable Resistor Malfunctions (1) Damage to the carbon film of the variable resistorThe carbon film of the variable resistor is worn or burned. At this time, the contact between the moving piece and the carbon film is poor or cannot be contacted.(2) Poor contact between the moving piece of the variable resistor and the carbon film causes the contact resistance between the moving piece and the carbon film to increase.(3) The variable resistor pin is broken. 8.3 Methods For Repairing Variable Resistor (1) When the track of the contact of the moving blade on the carbon film is worn, the contact on the moving blade can be bent inward to change the original track of the contact of the moving blade.(2) The contacts of the moving blade are dirty. You can clean the contacts with pure alcohol.(3) There is a disconnection between one stator and the carbon film. At this time, if it is used as a variable resistor (not used as a potentiometer), this stator that is not disconnected can be used instead. Resistance value.(4) A pin is broken due to twisting. A lead can be welded with a hardwire as a pin.Figure10. Test a Variable Resistor8.4 Testing a Variable Resistor with a Multimeter8.4.1 MethodThe detection method of the variable resistor is basically the same as that of the resistor. The resistance between the primers is measured with an ohmic block. The measurement can be performed directly on the circuit board, or the variable resistor can be disconnected from the circuit. (1) Measure the nominal resistance of the variable resistor. The multimeter is placed in the proper range of the ohmic block. The two-meter bars are connected to the two fixed pin pins of the variable resistor. At this time, the measured resistance value should be equal to the nominal resistance value of the variable electrical accessory, otherwise, the variable resistance is explained. The device is damaged. (2) Measure the resistance between the moving resistor and the stator of the variable resistor. The multimeter is placed in the proper range of the ohmic block. One meter rod is connected to the fixed piece, and the other one is connected to the moving piece. In this measurement state, when the variable resistor moving piece is rotated, the needle is deflected and the resistance value increases from zero To the nominal value, or decrease from the nominal value to zero. 8.4.2 PrecautionsDue to the particularity of the variable resistor, the following issues should be noted during the detection process:(1) If the resistance between the moving piece and a fixed piece is 0Ω, at this time, you should see whether the moving piece has turned to the end of the fixed piece. To exclude the effects of external circuits). (2) If the resistance value between the moving piece and any certain piece is greater than the nominal resistance value, it means that the variable resistor has an open circuit fault. (3) In the measurement, if the measured resistance between a moving piece and a certain piece is less than the nominal resistance value, it does not mean that it is damaged, but you should look at the position of the moving piece, which is different from ordinary resistors. (4) When taking off the measurement, you can use the appropriate range of the multimeter's ohmic stop.-One rod is connected to the pin of the pad, and the other rod is connected to afoot. Then use a flat screwdriver to slowly rotate the pad in a clockwise or counterclockwise direction. At this time, the hands should continuously change from 0Ω to the nominal resistance. The same method is used to measure the change of wake value between another fixed film and a moving film. The measurement method and test result should be the same. In this way, the variable resistor is good, otherwise, the variable resistor is damaged.Figure11. Digital MultimeterIX Active Variable Resistors with Wide Range of Load ImpedancePower resistors, variable resistors, and other electronic loads are often used to test power supplies and voltage regulators, as shown in the following figure: Figure12. Active variable resistors with several orders of magnitude constant resistanceAlthough the function is the same as a mechanical potentiometer, it is based on an active device, which can provide a wide range of load resistance, high resistance adjustment resolution, and less heat than a mechanical potentiometer. Analyzing the circuit shown in the figure above, the voltage expressions of the non-inverting and inverting ends of the operational amplifier are: Figure13. FormulaThese two voltages are equal, so Figure14. FormulaThe whole circuit can be regarded as the resistance of the non-inverting terminal IN + and the inverting terminal IN-. The non-inverting and inverting equivalent resistances are constant and independent of the test voltage (VIN). RSENSE includes several series resistors that provide multiple orders of magnitude in impedance selection. For example, if 10Ω is required, the terminal is IN + and "B" near IN-1 (points A, C, and D are not connected). For high power loads, pay attention to the rated power of the sense resistor and nFET. The power supply of the operational amplifier can be a battery or any other DC power supply. Its maximum working current is only 20 μA. It is powered by a 9V battery. Under normal circumstances, the active load can be used for 1-2 years.X One Question Related to Variable Resistors10.1 QuestionVolume control regulator in a CD receiver, radio and amplifier also useA.transistorB.variable resistorC.thermistorD.fixed resistor10.2 AnswerB  XI FAQ1. What is a variable resistor do?A variable resistor gives the user more control over the resistance, as it allows for variance or for the resistor to be changed in order to meet the resistance requirements of the user. Changing the resistance as a user is actually very simple. 2. What are the two types of variable resistors?The different types of variable resistors include Potentiometer. Rheostat. Thermistor. 3. What is the difference between a variable resistor and a potentiometer?In the potentiometer, the resistance of the track remains the same as the wiper moves and only the potential on the wiper changes. In a variable resistor, the resistance of the track apparently changes as the wiper moves and short circuits more or less of the track resistance. 4. What is the advantage of a variable resistor?The advantage of variable resistors is that you have more control over the voltage. You can also adjust the amount of voltage flowing through a circuit. 5. What is the symbol of a variable resistor?A variable resistor also called an adjustable resistor, consists of two terminals, where one of the terminals is a sliding or moving contact often known as a wiper. The variable resistor IEC symbol is represented by a rectangular box and an arrow across (or above) it, like that shown in the figure below. 6. How do you identify a variable resistor?The variable resistor is represented by a zig-zag line and an arrow across (or above) it, like that shown in the figure below. 7. How many types of variable resistors are there?Variable resistors can be categorized into three types: Potentiometers. Rheostats. Digital potentiometers. 8. Is LDR a variable resistor?An LDR is a component that has a (variable) resistance that changes with the light intensity that falls upon it. This allows them to be used in light sensing circuits. 9. Do variable resistors have polarity?Resistors are blind to the polarity in a circuit. Thus, you don't have to worry about installing them backward. Current can pass equally through a resistor in either direction. 10. Why is a variable resistor needed in a circuit?Simply put, a variable resistor is able to have its electrical resistance adjusted. These devices are used when working with electrical circuitry because they help to control voltage and/or currents. They specifically work with voltage and currents that are a part of the circuit.