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2026 Executive Summary: Discharging a capacitor safely is a critical maintenance step to prevent severe electrical shocks and equipment damage. In 2026, with the rapid expansion of high-voltage EV inverters and renewable energy grid systems, proper discharge protocols using dedicated resistors or discharge tools are more important than ever. This guide covers the working principles, safety procedures, and step-by-step methods for discharging both low and high-voltage capacitors safely.IntroductionMaintenance technicians and electronics hobbyists frequently experience electrical shocks from devices long after they have been unplugged. The primary component responsible for this dangerous phenomenon is the capacitor. From industrial power capacitors and modern EV inverter filter capacitors to the graphite coating of legacy CRT televisions, capacitors can store lethal amounts of electrical charge (often exceeding 300V) in fractions of a second. If maintenance personnel accidentally touch a charged terminal, the resulting electric shock can cause severe secondary injuries, such as falls or involuntary contact with other live circuits. Therefore, verifying zero energy state and manually discharging the capacitor is a mandatory safety protocol before beginning any repair work. This article details the industry-standard methods for safely discharging capacitors, explains the underlying physics of capacitance, and outlines the working principles of various capacitor types used in 2026. If you need to calculate the exact discharge rate of a capacitor under a known capacitance and charge it through a fixed value resistor, we recommend using Apogeeweb's Capacitor Safety Discharge Calculator.Figure 1. Apogeeweb's Capacitor Safety Discharge CalculatorTable of ContentsIntroductionTable of ContentsI. How Does a Capacitor Charge and Discharge?II. How to Safely Discharge a Capacitor?  2.1 Discharge Method After the Capacitor is Cut Off  2.2 Critical Safety Notes for Capacitor Discharge  2.3 The Physics of the Charging and Discharging ProcessIII. Three Methods to Discharge High Voltage Capacitors  3.1 What is a High Voltage Capacitor?  3.2 Step-by-Step High Voltage Discharge MethodsIV. How to Discharge Low Voltage Capacitors?  4.1 Short-circuiting with Wires  4.2 Using a Digital Multimeter  4.3 Safety PrecautionsV. How to Discharge a Filter Capacitor?  5.1 Discharge Techniques for Filter Capacitors  5.2 Calculating Charge and Discharge Time ConstantsVI. Fast Discharge Methods for Power Compensation and Electrolytic CapacitorsVII. How Does a Capacitor Bank Discharge Coil Work?  7.1 Principle of Capacitor Bank Discharge Coils  7.2 Influence of the Connection ModeVIII. How to Test Capacitors Using the Discharge PrincipleIX. Test Your Knowledge: Capacitor QuizX. Frequently Asked QuestionsI. How Does a Capacitor Charge and Discharge?When a capacitor charges, it stores electrical energy in an electrostatic field between two conductive plates, and when it discharges, it releases this stored energy back into the circuit to power a load. A capacitor is a passive electronic component composed of two conductive parallel plates separated by an insulating dielectric material.Figure 2. The Function of CapacitorsDuring the charging process, the power supply forces charged particles through the circuit, causing the potential difference between the two plates to gradually approach the voltage of the power source. Ultimately, opposite polarities of charge accumulate on the plates, bound by the dielectric, storing electrical energy as an electrostatic field. During the discharge process, the capacitor acts as a temporary power source. It moves the stored charged particles through a closed circuit, neutralizing the potential difference between the plates. The electrostatic field collapses, and the stored energy is converted into work consumed by the connected electrical load.II. How to Safely Discharge a Capacitor?To safely discharge a capacitor, you must create a controlled closed loop using a high-wattage resistor or a dedicated discharge tool to slowly neutralize the stored potential difference without creating dangerous sparks. Watch this demonstration video first:A practical capacitor lesson demonstrating the effects of uncontrolled discharge.2.1 Discharge Method After the Capacitor is Cut OffWhen a capacitor is disconnected from an energized circuit, it retains its stored voltage. If the circuit contains bleed resistors or other continuous loads, it will discharge slowly. Otherwise, it must be discharged manually by creating a short circuit through a resistive load (or a direct wire for very low voltages). When discharging, the external circuit and the capacitor form a closed loop. The excess electrons (negative charges) travel toward the positive electrode to achieve electrostatic balance. This current flow neutralizes the charges on both ends of the capacitor. Once neutralization is complete, the electric field disappears. However, because real-world circuits always contain some resistance, the charge decays exponentially. It trends infinitely toward zero but technically never reaches absolute zero, though it quickly drops to safe handling levels.Figure 3. Discharge Tools2.2 Critical Safety Notes for Capacitor DischargeAfter the capacitor is disconnected from the main bus, it must be discharged through a high-wattage discharge resistor or a special voltage transformer.Discharge must occur between the lead wires of the capacitor, and subsequently between the lead wires and the metal casing.The capacitor should be physically grounded only after the initial resistive discharge is complete.Before handling the capacitor, a test discharge must be performed by holding the discharge rod on the terminals for several seconds.Even if both sides of a capacitor bank are grounded, residual charges can remain. Each individual capacitor in a parallel group must be discharged separately.Exercise extreme caution with damaged capacitors. Internal disconnections can prevent standard grounding devices from fully discharging the unit.If the capacitor enclosure features an interlocking safety device, ensure the protective fence is only opened after the entire system is verified as grounded.2.3 The Physics of the Charging and Discharging ProcessSuppose a capacitor has upper and lower plates, with the upper plate connected to the positive electrode and the lower plate to the negative electrode. Upon connection to a DC power supply, a potential difference forms. The positive charges remain stationary in the atomic lattice, while the negative charges (electrons) are repelled from the negative terminal of the supply and accumulate on the bottom plate. This electron movement creates a growing potential difference across the plates. The voltage increases until it perfectly matches the power supply voltage, at which point the capacitor is fully charged and current ceases to flow. After disconnecting the power, the dielectric insulation prevents the charges from recombining. The potential difference persists until a conductive path is provided. When we discharge the capacitor by connecting the plates with a wire or resistor, electrons flow from the negatively charged plate back to the positive plate until electrostatic equilibrium is restored.Figure 4. Charge and DischargeIII. Three Methods to Discharge High Voltage Capacitors3.1 What is a High Voltage Capacitor?High-voltage capacitors are heavy-duty components designed to handle extreme electrical loads, commonly found in microwave ovens, medical imaging equipment, and modern EV charging infrastructure. They consist of outlet porcelain bushings, capacitive element groups, and a sealed steel shell. The internal elements use capacitor paper, film-paper composites, or pure synthetic films as the dielectric, with aluminum or platinum plates. To meet high withstand voltage requirements (often exceeding 10kV), internal capacitive elements are connected in series or parallel. Many modern high-voltage capacitors are equipped with internal bleed resistors designed to reduce residual voltage below 75V within 10 minutes of disconnection, though manual discharge remains a mandatory safety requirement.Figure 5. Microwave High Voltage Capacitor3.2 Step-by-Step High Voltage Discharge MethodsHigh-voltage capacitors must never be short-circuited directly with a screwdriver, as the massive instantaneous current can melt the contacts, vaporize the metal, and cause an explosion. Instead, the energy must be dissipated slowly using a resistive load. Here are three safe methods:Method 1: The High-Wattage Resistor MethodFirst, unplug the electrical power and verify the equipment is isolated from the mains.Obtain a 20,000-ohm, 2-watt (or higher, such as 5W) wire-wound resistor.Using insulated pliers, hold the resistor and touch its probes across the two terminals of the capacitor for several seconds.If the capacitor has three terminals, discharge between the outer terminal and the center terminal, then repeat for the remaining outer terminal.Method 2: The Alligator Clip MethodConnect one end of a high-wattage resistor to an insulated test lead and the other end to an insulated alligator clip. Wrap exposed connections in electrical tape.Clamp the alligator clip securely to the equipment's chassis ground wire.Use the test lead probe to touch the positive terminal of the capacitor. This routes the discharge safely to ground without generating sparks.Note: If discharging multiple capacitors consecutively, the resistor will generate significant heat. Use a 5W or 10W resistor for heavy-duty applications.Method 3: The Bulb or Soldering Iron MethodConstruct a discharge rig using a 100-200 watt incandescent bulb (or a 60-80W electric soldering iron) connected to two insulated probes.Touch the probes to the capacitor terminals. The bulb will flash brightly and dim as the capacitor discharges, providing a visual indicator of the voltage drop.Once the bulb is completely dark, verify the voltage is zero using a multimeter.IV. How to Discharge Low Voltage Capacitors?4.1 Short-circuiting with WiresFor low-voltage capacitors operating below 50V or with a capacity under 1μF, you can safely discharge them by directly short-circuiting the two poles with an insulated wire or screwdriver. While a screwdriver is common, it can leave carbonized burn marks on the terminals. Never use this direct short-circuit method for high-voltage or large-capacity capacitors, as the rapid energy release will create dangerous sparks and potentially damage the component.Figure 6. Shortcircuit4.2 Using a Digital MultimeterYou can safely discharge small capacitors using the resistance setting (Ohms) on a digital multimeter. Set the multimeter to a high resistance range (e.g., 100K or 200K ohms) and place the probes on the capacitor terminals. The internal battery of the multimeter will interact with the capacitor, and you will see the resistance reading climb or drop until it stabilizes, indicating the charge has been neutralized. Disconnect the probes immediately after the reading stabilizes to prevent reverse charging.Figure 7. Multimeter4.3 Safety PrecautionsBecause capacitors exhibit dielectric absorption (often called "battery action"), they can slowly rebuild a small residual charge even after being discharged. Always manually discharge a capacitor immediately before handling it, even if the equipment has been unplugged for days. When working with industrial capacitor banks, ensure the circuit breaker and isolation switches are open, and wear appropriately rated insulating gloves.V. How to Discharge a Filter Capacitor?5.1 Discharge Techniques for Filter CapacitorsA filter capacitor is an energy storage device installed at the output of a rectifier circuit to smooth out AC pulsations and provide a stable DC output. In a standard 220V AC to DC power supply, the voltage across the primary filter capacitor can reach approximately 310V DC. To discharge a 310V filter capacitor, the best tool is a 25W electric soldering iron or a dedicated power resistor. A 25W soldering iron has an internal resistance of about 2.2KΩ. According to Ohm's Law (I = U/R), the maximum initial discharge current is 310V / 2200Ω = 140mA. This low current safely drains a several-hundred microfarad capacitor in a few seconds without generating sparks. Avoid using a 25W incandescent bulb for 310V filter capacitors. The cold resistance of a 25W tungsten filament is only about 160Ω, resulting in an instantaneous current surge of nearly 2 amps, which can instantly burn out the filament.Figure 8. Filter Capacitors5.2 Calculating Charge and Discharge Time ConstantsThe charging and discharging time of a filter capacitor is dictated by the RC time constant (T = R × C), where R is the circuit resistance and C is the capacitance. The time required for the capacitor voltage to reach 63.2% of the supply voltage is one time constant. After 5 time constants (5T), the capacitor is considered 99.3% fully charged or discharged. Charging Calculation: If a rectifier diode has an internal forward resistance of 30Ω and the filter capacitor is 2200μF, the charging time constant is Tc = 30Ω × 0.0022F = 0.066 seconds (66ms). Discharging Calculation: If the connected load has a resistance of 300Ω, the discharge time constant is Td = 300Ω × 0.0022F = 0.66 seconds (660ms). It will take approximately 3.3 seconds (5 × 660ms) for the capacitor to fully discharge through the load once power is removed.Figure 9. (a) Charging Curve (b) Discharging CurveFigure 10. Bridge Rectifier CircuitRelated recommendation: Apogeeweb's time constant calculator.VI. Fast Discharge Methods for Power Compensation and Electrolytic Capacitors(1) Power Factor Compensation CapacitorsPower factor compensation capacitors, rated in kVAR, are large non-polar capacitors used to stabilize industrial power grids. Modern units are equipped with internal discharge resistors designed to drop the voltage below 50V within 3 minutes of disconnection. However, technicians must still manually discharge them using a high-power resistor probe before maintenance, as they operate at grid voltages (220V to 480V+).Figure 11. Reactive Power Compensation Supplied by Capacitors(2) Operating Skills for Electrolytic CapacitorsSmall Lead-Type: Can be directly short-circuited, though using a 100-ohm resistor is always safer for the component's lifespan.Snap-in/Horn Type: Use a 220V/60W bulb or a dedicated 1KΩ 5W resistor to discharge slowly.Large Bolt-Type: For high-voltage industrial electrolytics, use a dedicated discharge coil. Alternatively, a long (5-meter) coiled wire with alligator clips can be used; the length and coiling provide enough inductive and resistive load to dissipate the energy as heat safely.VII. How Does a Capacitor Bank Discharge Coil Work?A discharge coil is a mandatory safety device installed in parallel with high-voltage capacitor banks in substations. It rapidly drains the residual charge from the capacitors when they are disconnected from the grid, preventing dangerous overvoltage conditions during re-closing and ensuring the safety of maintenance personnel.7.1 Principle of Capacitor Bank Discharge CoilsThe discharge coil acts as a voltage transformer. Its primary winding is connected across the capacitor bank, bearing the full operating voltage. When the power is cut, the coil provides a low-resistance path for the DC charge to dissipate rapidly. For large capacity capacitor banks (≥1.7Mvar), a dedicated discharge coil must be used instead of a standard voltage transformer (PT) to prevent the PT from overheating and exploding under the massive discharge current.7.2 Influence of the Connection ModeDischarge coils are typically used in 66kV and below power systems. Their secondary windings are often wired in an open delta configuration to provide internal fault protection for the capacitor bank. If the discharge coil is used to directly monitor the capacitor's terminal voltage, jumper connection methods cannot be used, as they would distort the voltage readings required for accurate protective relaying.VIII. How to Test Capacitors Using the Discharge PrincipleYou can test the health of a capacitor (checking for breakdown, leakage, or failure) using an analog multimeter. This test relies on the multimeter's internal battery charging the capacitor, and the subsequent discharge behavior.Normal: The multimeter pointer swings rapidly to the right (low resistance) as the capacitor charges, then slowly returns to "∞" (infinite resistance) as it fully charges and blocks DC current.Leakage: The pointer swings to the right but fails to return all the way to "∞", stopping at a specific resistance value. This indicates the dielectric is leaking current.Open Circuit: The pointer does not move at all and stays at "∞". (Note: Very small capacitors under 5000pF may not show a visible swing on standard meters).Short Circuit: The pointer swings to "0" ohms and stays there, indicating the internal dielectric has completely failed.Figure 12. (a) Normal; (b) Breakdown; (c) FailureIX. Test Your Knowledge: Capacitor QuizWhich of the following determines the charging and discharging rate of a capacitor?a) Time constantb) Currentc) Powerd) VoltageAnswer: aExplanation: The time constant (T = R × C) in an RC circuit dictates the speed of charge and discharge. A smaller time constant results in a faster charging and discharging rate. Frequently Asked QuestionsWhat is the safest tool to discharge a capacitor?The safest tool to discharge a capacitor is a dedicated capacitor discharge pen or a high-wattage resistor (such as a 20,000-ohm, 5-watt resistor) connected to insulated alligator clips. These tools safely dissipate the stored electrical energy as heat without creating dangerous sparks or damaging the capacitor terminals.How long does it take for a capacitor to discharge naturally?A disconnected capacitor can take anywhere from a few minutes to several months to discharge naturally, depending on its internal leakage resistance and dielectric material. Because high-voltage capacitors can retain lethal charges for weeks, you must always manually discharge and verify them with a multimeter before handling.Why shouldn't I use a screwdriver to discharge a capacitor?Using a screwdriver to short-circuit a capacitor causes an instantaneous, uncontrolled energy release. This rapid discharge can generate dangerous sparks, melt the capacitor's terminals, damage the screwdriver, and potentially cause the capacitor to explode. Always use a proper resistive load to control the discharge rate safely.Can a capacitor hold a charge without power?Yes, a capacitor is specifically designed to store electrical energy and will hold its charge long after the main power supply is disconnected. This residual charge acts like a temporary battery, which is why capacitors pose a severe shock hazard in unplugged electronic devices and power supplies.{ "@context": "https://schema.org", "@graph":[ { "@type": "Article", "headline": "How to Safely Discharge a Capacitor: 2026 Guide", "datePublished": "2020-09-10", "dateModified": "2026-03-20", "author": { "@type": "Organization", "name": "Apogeeweb" }, "publisher": { "@type": "Organization", "name": "Apogeeweb" }, "description": "A comprehensive 2026 guide on how to safely discharge high and low voltage capacitors, including step-by-step methods, safety tools, and the physics of RC time constants." }, { "@type": "FAQPage", "mainEntity":[ { "@type": "Question", "name": "What is the safest tool to discharge a capacitor?", "acceptedAnswer": { "@type": "Answer", "text": "The safest tool to discharge a capacitor is a dedicated capacitor discharge pen or a high-wattage resistor (such as a 20,000-ohm, 5-watt resistor) connected to insulated alligator clips. These tools safely dissipate the stored electrical energy as heat without creating dangerous sparks or damaging the capacitor terminals." } }, { "@type": "Question", "name": "How long does it take for a capacitor to discharge naturally?", "acceptedAnswer": { "@type": "Answer", "text": "A disconnected capacitor can take anywhere from a few minutes to several months to discharge naturally, depending on its internal leakage resistance and dielectric material. Because high-voltage capacitors can retain lethal charges for weeks, you must always manually discharge and verify them with a multimeter before handling." } }, { "@type": "Question", "name": "Why shouldn't I use a screwdriver to discharge a capacitor?", "acceptedAnswer": { "@type": "Answer", "text": "Using a screwdriver to short-circuit a capacitor causes an instantaneous, uncontrolled energy release. This rapid discharge can generate dangerous sparks, melt the capacitor's terminals, damage the screwdriver, and potentially cause the capacitor to explode. Always use a proper resistive load to control the discharge rate safely." } }, { "@type": "Question", "name": "Can a capacitor hold a charge without power?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, a capacitor is specifically designed to store electrical energy and will hold its charge long after the main power supply is disconnected. This residual charge acts like a temporary battery, which is why capacitors pose a severe shock hazard in unplugged electronic devices and power supplies." } } ] }, { "@type": "HowTo", "name": "How to Discharge a High Voltage Capacitor", "description": "Step-by-step instructions for safely discharging a high voltage capacitor using a high-wattage resistor.", "step":[ { "@type": "HowToStep", "name": "Isolate Power", "text": "First, unplug the electrical power and verify the equipment is isolated from the mains." }, { "@type": "HowToStep", "name": "Prepare the Resistor", "text": "Obtain a 20,000-ohm, 2-watt (or higher, such as 5W) wire-wound resistor." }, { "@type": "HowToStep", "name": "Discharge the Terminals", "text": "Using insulated pliers, hold the resistor and touch its probes across the two terminals of the capacitor for several seconds." }, { "@type": "HowToStep", "name": "Discharge Multi-Terminal Capacitors", "text": "If the capacitor has three terminals, discharge between the outer terminal and the center terminal, then repeat for the remaining outer terminal." } ] } ]}

IntroductionCapacitors are components that store electricity and electrical energy (potential energy) and play an important role in circuits such as tuning, bypassing coupling, and filtering. Capacitors are connected in parallel to increase capacity, and capacitors are connected in series to decrease capacity. When the capacitor is connected in series in the circuit, it can prevent the sudden change of voltage and absorb the overvoltage in the peak state. The series resistance plays a damping role, and the resistance consumes the energy of the overvoltage, thereby suppressing the oscillation of the circuit. When the capacitor is connected in parallel, the parallel resistor can absorb the electric energy of the capacitor, prevent the discharge current of the capacitor from being too large, and avoid damaging the devices (such as thyristors) connected in parallel with it. This is a very comprehensive article including the calculation formulas, circuits, and related common problems of series capacitors and parallel capacitors.Capacitors in Series & Parallel - Electronics BasicsCatalogIntroductionCatalogI What are the Capacitors in Series and Parallel?II Calculation Methods of Capacitance of a Series/Parallel Network  2.1 The Series and Parallel Combination  2.2 Voltage Division  2.3 How to Divide the Voltage When Capacitors are Connected in Series?  2.4 What is the Voltage Division Formula When Connecting 2 Capacitors in Series?III The Equivalent Method of Series or Parallel Connection of Capacitors with Different Rated Voltages and CapacitiesIV Comparison Table of Capacitors in Series and Parallel  4.1 Calculation Comparison of Capacitors in Series and Parallel  4.2 Correspondence Between Magnetic Circuit and Electric Circuit  4.3 Basic Physical Quantities of Magnetic Field and Magnetic CircuitV Frequently Asked Questions about Capacitors in Series and ParallelVI Electrolytic Capacitors in Series  6.1 Function and Purpose of 2 Electrolytic Capacitors in Anti-phase Series  6.2 Is the Electrolytic Capacitor in Series a Non-polarised Capacitor?VII QuizVIII FAQI What are the Capacitors in Series and Parallel?1.1 Parallel Connection of CapacitorsWe can describe the capacitors in parallel as a "water tank", but the water tank stores water, and the capacitor stores electric charges. If multiple capacitors are connected in parallel, they can naturally store more charge.(1) The equivalent capacitance after parallel connection is equal to the sum of the capacitance of each capacitance;(2) The voltage at both ends of each capacitor after parallel connection is equal;The withstand voltage after parallel connection is equal to the smallest capacitor voltage, and the equivalent capacitance is C1+C2, as shown in the figure below.Figure1. Parallel Connection of Capacitors1.2 Series Connection of Capacitors(1) The equivalent capacitance capacity after series connection is equal to the sum of the reciprocal of each capacitance;(2) The capacitance of each capacitor after series connection is equal;(3) The withstand voltage after series connection is equal to the sum of each capacitor voltage.After the capacitor is connected in series, it is equivalent to increase the distance between the two poles. The more the number in series, the smaller the capacitance, but the higher the withstand voltage. In actual circuit design, we generally rarely use capacitors in series, but capacitors in parallel are often used. Sometimes the capacity of a single capacitor is not enough, and one more is added.Figure2. Series Connection of CapacitorsII Calculation Methods of Capacitance of a Series/Parallel Network2.1 The Series and Parallel Combination(1) How to calculate the series capacitance of a capacitor?Suppose there are n capacitors connected in series. The series combination of these n capacitors is connected across a voltage source of V volts. Let us consider that the voltages across capacitors 1, 2, 3...n are V 1, V 2, V 3... Vn, respectively. The capacitances of capacitors 1, 2, 3 ... n are C 1, V 2, V 3 ... C n farad. Since all capacitors are connected in series, each of them will get the same charge, ie it is Q Coulomb. Now we know that the charge at both ends of the capacitor is only the product of the potential difference between the two ends of the capacitor and its capacitance value.Since the series combination of these capacitors is connected across the source of the voltage V volts, replacing the series combination n of multiple capacitors.If we consider a single equivalent capacitor of C,Now we get from equations 1 and 2,Therefore, when multiple capacitors are connected in series, the reciprocal of the equivalent capacitance of the system is given by the arithmetic sum of the reciprocal of their respective capacitances. (2) How to calculate the capacitance in parallel circuits?Suppose there are n capacitors connected in parallel. The parallel combination of these n capacitors is connected across the V volt voltage source. Since the capacitors are connected in parallel to the same voltage source, the charge of each capacitor is different and depends on their respective capacitance values. Let us consider that the charges of capacitors 1, 2, 3...n are Q 1, Q 2, Q 3,..., Q n coulombs, respectively. The capacitances of capacitors 1, 2, 3,..., n are C_1, C_2, C_3,... C_n coulombs respectively. It is now known that a charging capacitor is just the product of the voltage across the capacitor and its capacitance value. therefore,Now instead of connecting multiple capacitors in parallel, if we connect a single equivalent capacitor with capacitance C across the voltage source, then the total charge at both ends of the equivalent capacitor,Since all capacitors are connected in parallelWe can get from equations 1 and 2,Therefore, when multiple capacitors are connected in parallel, the capacitance of the system is given by the arithmetic sum of their respective capacitances.Figure3. (a) Three capacitors are connected in parallel. Each capacitor is connected directly to the battery.              (b) The charge on the equivalent capacitor is the sum of the charges on the individual capacitors. (3) Other related calculation formulasWhen the capacitor is connected in parallel, the area of the electrode is increased, and the capacitance is increased. The total capacity when connected in parallel is the sum of each capacity. When the capacitors are connected in series, the resistance value of the capacitor should be smaller than the insulation resistance of the capacitor in parallel to make the voltage distribution on each capacitor even, so as not to damage the capacitor due to uneven voltage distribution. The series and parallel calculations of capacitors are just the opposite of the series and parallel calculations of resistors.Voltage is the voltage during charging. The relationship between capacity and current, voltage is similar to power and is related to load.When voltage and capacity are quantitative, the smaller the load resistance, the larger the current and the shorter the time.When the voltage and load are quantitative, the larger the capacity, the longer the current and the longer the time.But in the actual discharge circuit, the general load is unchanged, the voltage of the capacitor is gradually reduced, and the current is gradually reduced. (1) Electric capacity (uf) = current (mA)/15Current limiting resistance (Ω)=310/maximum allowable surge currentDischarge resistance (KΩ)=500/capacitance (uf) (2) Calculation method C=15×IC is the capacitance of the capacitor, the unit is microfarad; the i device is the working current, the unit is ampere.For example, if the resistance of a bulb is 0.6 amps, the capacitance should be 15×0.6=9 microfarads, and a 9 microfarad capacitor in series is sufficient. (3) Empirical formula, 1uF output 50mA (if it is linear, a 10000F super capacitor can reach a surge current of 500 megaamps) (4) The calculation of the half-wave rectification method should provide about 30mA current per uF capacitance, which is a reference on the 50Hz220V line in China.The current is doubled in full-wave rectification, that is, 60mA current can be provided per uF.Formula: R*C≥(3～5)*T/2, you need to know the frequency of the lowest signal in the ripple component (that is, the maximum T), and then determine the value of C. ● Capacitor capacityCapacitor capacity indicates the size of electric energy that can be stored. The obstructive effect of capacitors on AC signals is called capacitive reactance. The capacitive reactance is related to the frequency and capacitance of the AC signal. The capacitive reactance XC=1/2πf c (f represents the frequency of the AC signal, and C represents the capacitance of the capacitor). ● The capacity unit and withstand voltage of the capacitor.The basic unit of capacitance is F (farad), and other units include: millifarad (mF), microfarad (uF), nanofarad (nF), picofarad (pF). Since the capacity of the unit F is too large, we generally see units of μF, nF, and pF. Conversion relationship: 1F=1000000μF, 1μF=1000nF=1000000pF. Each capacitor has its withstand voltage value, denoted by V. Generally, the nominal withstand voltage of the electrodeless capacitor is relatively high: 63V, 100V, 160V, 250V, 400V, 600V, 1000V, etc. The withstand voltage of polar capacitors is relatively low. Generally, the nominal withstand voltage values ​​are: 4V, 6.3V, 10V, 16V, 25V, 35V, 50V, 63V, 80V, 100V, 220V, 400V, etc. Power capacitor calculation: such as a three-phase capacitor bank with a nominal voltage of 690v and a capacity of 15kvar. Used in 600v circuit, delta connection, the actual effective capacity is: s=15kvar*600*600/(690*690)=11.34kvar. That is: the capacity and voltage are proportional to the square.2.2 Voltage DivisionDue to the large capacity of large capacitors, the volume is generally large, and they are usually made by multi-layer winding, which leads to a relatively large distributed inductance of large capacitors (also called equivalent series inductance, or ESL for short). The impedance of the inductor to the high frequency signal is very large, so the high frequency performance of the large capacitor is not good. Some small-capacity capacitors are just the opposite. Because of their small capacity, the volume can be made small (shortening the lead wire reduces the ESL, because a piece of wire can also be regarded as an inductance), and flat capacitors are often used Structure, such a small capacity capacitor has a small ESL so that it has a good high frequency performance, but due to the small capacity, the impedance to low frequency signals is large. So, if we want to pass the low frequency and high frequency signals well, we use a large capacitor and then a small capacitor.The commonly used small capacitor is 0.1uF CBB capacitor is better (ceramic capacitor is also OK), when the frequency is higher, you can also connect smaller capacitors in parallel, such as a few pF, hundreds of pF. In digital circuits, a 0.1uF capacitor is generally connected to the ground in parallel to the power pin of each chip (this capacitor is called a decoupling capacitor, of course, it can also be understood as a power filter capacitor, the closer the chip is, the better), because The signal in these places is mainly high-frequency signal, and it is enough to use a smaller capacitor to filter. The impedance of an ideal capacitor decreases as the frequency increases (R = 1/jwc), but an ideal capacitor does not exist. Due to the distributed inductance effect of the capacitor pins, the capacitor is no longer a simple capacitor in the high frequency range. , It should be regarded as a series high-frequency equivalent circuit of capacitance and inductance. When the frequency is higher than its resonance frequency, the impedance shows the characteristic of increasing with the increase of frequency, which is the inductance characteristic. At this time, the capacitance is like An inductance. On the contrary, inductors have the same characteristics. Large capacitors in parallel with small capacitors are widely used in power supply filtering. The fundamental reason is the self-resonance characteristics of the capacitor. The combination of large and small capacitors can well suppress low-frequency to high-frequency power interference signals. Small capacitors filter high frequencies (high self-resonant frequency), and large capacitors filter low frequencies (low self-resonant frequency). The two complement each other. ● Series voltage divider ratio: V1 = C2/(C1 + C2)*V...the larger the capacitance, the smaller the voltage divided, which is the same under AC and DC conditions● Parallel shunt ratio: I1 = C1/(C1 + C2)*I...The larger the capacitance, the larger the current that passes. Of course, this is under AC conditions.Explanation: When two or more capacitors are connected in series, it is equivalent to lengthening the insulation distance, because only the two polar plates on the two sides work, and because the capacitance is inversely proportional to the distance, the distance increases and the capacitance decreases; two or two When the above capacitors are connected in parallel, the area equivalent to the plate increases, and because the capacitance is proportional to the area, the area increases and the capacitance increases. ● Capacitors in series: After the capacitors are connected in series, the capacity decreases and the withstand voltage increases. Formula: 1C1+1C2=1C If two 50uf are connected in series, it becomes 25uf.● Withstand voltage = add the withstand voltage values ​​of two capacitors. If two 100V withstand voltages are connected in series, it becomes 200V.● The formula for calculating the capacity of the series circuit of the capacitor C: 1/C=1/C+1/C2+1/C3+.+1/CnC is the total capacitance value of the capacitor series circuit, C1, C2, C3, Cn are the capacitance values of each capacitor in the capacitor parallel circuit, that is, the reciprocal of the total capacitance of the series circuit is equal to the sum of the reciprocal of the capacitance of each capacitor in the series circuit.Figure4. Capacitors in Series and Parallel2.3 How to Divide the Voltage When Capacitors are Connected in Series?For example 4V voltage source, two capacitors of 0.5F and 1F in series. If it is a DC voltage source, according to the characteristics of capacitor series voltage division introduced in middle school physics:(1) The total voltage across the capacitor series circuit is equal to the sum of the divided voltages across the capacitors. That is, U= U1+ U2+ U3+…+Un.(2) When capacitors are connected in series, the voltage distributed on each capacitor is inversely proportional to its capacitance. That is, Un = Q / Cn (because in the capacitor series circuit, the amount of charge carried on each capacitor is equal, so the larger the capacitor, the lower the voltage, and the smaller the capacitor, the higher the voltage. .)Then the voltage source of 4V, the voltage on the two capacitors of 0.5F and 1F are 8/3V and 4/3V respectively 2. If it is an AC voltage source, from the impedance of the capacitor Xc=1/jωC, we can see |Xc| and C In inverse proportion, the same result can be obtained by using |Xc| as a resistor to calculate the voltage divider.2.4 What is the Voltage Division Formula When Connecting 2 Capacitors in Series?This is a theoretical calculation problem. It is necessary to assume that the withstand voltage value of the capacitor has no margin, that is, a capacitor of 200pF is breakdown when it exceeds 500V; a capacitor of 300pF is breakdown when it exceeds 900V.After adding 1000V voltage, the 200pF capacitor will withstand 600V voltage. Regardless of the capacitor's withstand voltage margin, the 200pF capacitor will break down; at this time, 1000V will all be added to the 300pF capacitor, which exceeds its withstand voltage, so it will breakdown. Calculation formula:If there are M capacitors connected in series, the actual voltage value Un of any capacitor Cn is:Un=U*C/Cn Among them: U is the total voltage; C is the total capacity of M capacitors in series.For two capacitors in series, the formula evolves into:Assuming that the total voltage is U, the voltages on C1 and C2 are U1 and U2 respectively, thenU1=C2*U/(C1+C2)U2=C1*U/(C1+C2)III The Equivalent Method of Series or Parallel Connection of Capacitors with Different Rated Voltages and CapacitiesThe equivalent method of using capacitors with the same rated voltage in series or in parallel is relatively simple and commonly used.Several capacitors with different rated voltages and different capacities are connected in series or in parallel, and the equivalent methods are different. Now give examples to illustrate. There are three capacitors C1: 220µF /10V C2: 100µF/25V C3: 10µF/100VCalculate their parallel and series equivalent values ​​respectively. (1) Parallel equivalent method1) Equivalent capacitanceC and = C1 + C2 + C3= 220µF + 100µF + 10µF/= 330µF2) Equivalent withstand voltageU parallel = U1 = 10V (take the minimum withstand voltage value U1) (2) Series equivalent method1) Equivalent capacitance1/C string ==1/C1 + 1/C2 + 1/C3= 1/220 + 1/100 + 1/10= 252/2200C string == 2200/252≈ 8 (µF)2) Equivalent withstand voltage ● Compare the Q value of each capacitorQ1= C1 X U1 Q2=C2 X U2 Q3=C3 X U3= 220 X 10 =100 X 25 =10 X 100=2200 (C) =2500 (C) =1000 (C)Q = Q3 =1000 (C) (take the minimum power value Q3) ● Find the actual allowable withstand voltage value of each capacitorU1 (actual) = Q/C1 U2 (actual) = Q/C2 U3 (actual) = Q/C3= 1000/220 = 1000/100 = 1000/10≈4.5(V) = 10 (V) =100 (V)3) U string = U1 (actual) + U2 (actual) + U3 (actual)≈4.5 + 10 + 100≈114.5(V)Figure5. Equivalent CapacitanceIV Comparison Table of Capacitors in Series and Parallel4.1 Calculation Comparison of Capacitors in Series and Parallel4.2 Correspondence Between Magnetic Circuit and Electric Circuit4.3 Basic Physical Quantities of Magnetic Field and Magnetic CircuitV Frequently Asked Questions about Capacitors in Series and Parallel(1) Do capacitors charge faster in parallel or series?If two capacitors with the same capacity are connected in parallel or in series in the same circuit, the capacitor in series will charge faster, because the capacity of the capacitor is reduced by half after the capacitor is connected in series, and the charging time becomes shorter. The capacity of the capacitor after parallel connection is doubled, and the charging time will be longer for the same charging circuit. (2) The electric charge of each capacitor in the series circuit is equal. Why is the electric charge of each capacitor equal to the electric charge of the equivalent capacitor?Capacitor voltage: U=Q/CQ=I*tSo U=(I*t)/CWhen the capacitors connected in series are connected to the power supply, the capacitors start to charge. The current flowing through each capacitor is the same. As time goes by, the voltage of each capacitor increases. However, due to the different voltage rise rates of C, the sum of the voltage of each capacitor is equal to the power supply. When the voltage is applied, charging stops and the current is zero. Analyze this process: the current flowing through each capacitor during the entire charging process is the same, and the elapsed time is the same, so the current of each capacitor is the same over time, so the amount of charge is the same and equal to the capacity of the capacitor.Figure6. A Charging State of Three Capacitors in Parallel(3) Are the filter capacitors in the power amplifier power supply connected in parallel?The filter capacitor of the power amplifier power supply is set to eliminate some of the AC components contained in the rectification from AC to DC (the purpose is to improve the audio quality), so all capacitors with larger capacity are selected, generally using electrolysis above tens of microfarads Capacitor. The parallel connection of capacitors is the addition of the capacity of each capacitor, usually forming a standard type 1 filter circuit: "capacitor-resistor (or inductance)-capacitor". If the capacitors are connected in series, the capacity will decrease, it will only increase the cost and occupy more space, meaningless. The power supply line filter capacitor of the amplifier circuit of the power amplifier is generally grouped in parallel. Depending on the design of the power supply, the single power supply circuit may also be directly connected in parallel, or divided into two groups. The two groups are separated by power inductors or resistors into two filter circuits to form a pie-type filter circuit; if it is a dual power supply circuit, , It is generally divided into two groups as for the two groups of power lines. The easiest way to increase the filter capacitor of the power amplifier is to see the positive and negative poles and the rated withstand voltage. Connecting them in parallel can improve the stability of the DC voltage and improve the low-frequency characteristics of the amplifier, making the low frequency of the speaker sound more full and round. Capacitors are generally used in parallel, and capacitors of different capacities filter noise at different frequencies. Large-capacity capacitors can only be realized by electrolytic capacitors. Electrolytic capacitors have positive and negative polarity and are very loud when connected reversely.VI Electrolytic Capacitors in Series6.1 Function and Purpose of 2 Electrolytic Capacitors in Anti-phase SeriesIn some circuit designs, it is seen that two electrolytic capacitors are connected in series in the reverse phase. The capacity of the two components should be equal and the withstand voltage is the same. In AC circuits, the leakage current can be reduced. Just use a non-polar capacitor to get a large-capacity non-polar capacitor. . Large-capacity non-polar capacitors are more expensive. The electrolytic capacitor has a large capacity and is cheap, but it has a polarity, and the two are connected in reverse series. It is non-polar. It can only be used in very low voltage applications (up to 1-2V). The voltage is slightly higher. When the capacitor is used in the opposite direction, the leakage will be large. The accumulated effect will cause the electrolytic capacitor to heat up and eventually cause the capacitor to explode. Electrolytic capacitors are used in DC circuits. So its series connection should be the negative pole of the first one and the positive pole of the second (just like dry batteries in series). But in the circuit, there is indeed a case where the negative poles of two electrolytic capacitors are connected to the negative pole (inverted series), and the two positive poles are used. This is because it is used in an AC circuit (in a circuit where DC and AC coexist), There is no guarantee that the potential of one pole is always higher than the other pole), so that when the capacitor is under reverse voltage, serious leakage current will be generated. At this time, non-polar capacitors should be used, but non-polar capacitors are expensive and expensive. The volume is large, so some people use two electrolytic capacitors to "reverse series".  Its working state is that when there is alternating current, one of them is in the reverse state. Due to its serious leakage, the voltage drop across it is very small. Almost all of the voltage falls on the positive capacitor, and when the other half cycle of the alternating current, the state of the two capacitors will be exchanged, so these two capacitors are used as one, and the total capacitance is equal to any one of them. The total withstands voltage value is equal to 2 times of any capacitor.6.2 Is the Electrolytic Capacitor in Series a Non-polarised Capacitor?Of course, two electrolytic capacitors in parallel will not work. If two electrolytic capacitors are connected in series, it will still not work without applying a proper bias voltage. Applying a bias voltage is quite complicated, especially when both ends of the capacitor (two in series) are not grounded (the bias voltage must be floating). Considering the complexity of applying the bias voltage, it is better not to use this method: connect the negative poles of the two capacitors, and connect the two capacitors in parallel with a high-current diode. The positive of the diode is connected to the negative of the capacitor, and the negative is connected to the positive of the capacitor. Parallel connection of course still has polarity. If reverse parallel connection, it is non-polar, but it is non-polar. Reverse series connection is also not advisable. If you do a test, you will find that there must be a capacitor that withstands the backpressure. If the voltage is large, it will blow up. Unless special measures are taken, the voltage is always applied to the capacitor with the positive voltage. on. Two electrolytic capacitors of the same capacity can be connected in series, but a diode must be connected in anti-parallel to prevent the reverse breakdown of the electrolytic capacitor. After adding a diode, it is okay if it is used for filtering, but it is definitely not good for blocking DC. Because the electrolytic capacitor is only charged and not discharged. Two identical electrolytic capacitors connected in reverse series can replace non-polar capacitors with the same capacity. The dielectric loss of the electrolytic capacitor is very large, and it must be connected to the AC circuit after the voltage is greatly reduced. Otherwise, it is either burned or fried.VII Quiz● QuestionA network of five capacitors of C is connected to a 100 V supply, as shown below figure. Determine(a) the equivalent capacitance of the network(b) the charge on each capacitor. ● SolutionIn the given network, the top three Capacitance is in series, So equivalent capacitance of the top part1C1=1C+1C+1CC1=C3Similarly, the lower two Capacitance is in series, So equivalent capacitance of lower part1C2=1C+1CC2=C2 Now both C1 and C2 are in parallel, so equivalent Capacitance of the NetworkCeq=C1+C2=C3+C2=5C3Now Charge on top part will beQ1=C1V=CV3Now Charge on lower part will beQ2=C2V=CV2  VIII FAQ1. How do you solve capacitors in series and parallel?To calculate the total overall capacitance of a number of capacitors connected in this way you add up the individual capacitances using the following formula: CTotal = C1 + C2 + C3 and so on Example: To calculate the total capacitance for these three capacitors in parallel. 2. How do you know if a capacitor is in series or parallel?In your circuit current, all of the current going to one capacitor must also go to the other. Therefore they are in series. Hope this helps. If two (two-terminal) circuit elements are series-connected, they have identical (not just equal) currents through. 3. What is a capacitor in parallel?Capacitors are connected together in parallel when both of their terminals are connected to each terminal of another capacitor. The voltage ( Vc ) connected across all the capacitors that are connected in parallel is the same. 4. Can you put two capacitors in series?If two or more capacitors are connected in series, the overall effect is that of a single (equivalent) capacitor having the sum total of the plate spacings of the individual capacitors. With resistors, series connections result in additive values while parallel connections result in diminished values. 5. How are capacitors connected in series?Here are the rules for calculating capacitances in series: If the capacitors are of equal value, you're in luck. All you must do is divide the value of one of the individual capacitors by the number of capacitors. For example, the total capacitance of two, 100 μF capacitors is 50 μF. 6. Why capacitor is connected in parallel?Capacitors are devices used to store electrical energy in the form of electrical charges. By connecting several capacitors in parallel, the resulting circuit is able to store more energy since the equivalent capacitance is the sum of individual capacitances of all capacitors involved. 7. Do capacitors in series increase voltage?Capacitors connected in series will have lower total capacitance than any single one in the circuit. This series circuit offers a higher total voltage rating. The voltage drop across each capacitor adds up to the total applied voltage. This is why series capacitors are generally avoided in power circuits. 8. Do capacitors in series or parallel store more energy?The energy stored in a capacitor is a function of the voltage across the capacitor. The voltage will be higher when they are in parallel, so the parallel connection stores the most energy. 9. Why voltage is different in a series combination of capacitors?In a series combination, since the charge stored is the same as the same charge flows through all the capacitors, the potential difference across each will be different. 10. When capacitors are wired in parallel what must be the same for the two capacitors?The charge in the two capacitors is different. Capacitors connected in parallel are connected to the same start and end points of the input and output that's why they have the same potential difference.  

Executive Summary: Potentiometers in 2026A potentiometer (or "pot") is a three-terminal variable resistor used to control voltage, current, and signal processing in electronic circuits. While traditional mechanical pots remain vital for audio and industrial controls, 2026 trends favor high-precision Digital Potentiometers (DigiPots) and MEMS-based sensors for IoT and robotics applications. This guide covers the latest classification standards, modern applications, and essential maintenance tips for optimal circuit performance.Ⅰ. What is a Potentiometer? (2026 Overview)A potentiometer is a critical three-terminal passive electronic component that functions as an adjustable voltage divider. Ideally suited for applications requiring user-generated input or position sensing, it consists of a resistive element (track) and a sliding wiper. If only two terminals are configured (one end and the wiper), it functions as a variable resistor or rheostat. While the core mechanical construction of potentiometers remains consistent, modern 2026 manufacturing has introduced durable conductive plastics and cermet materials to extend lifecycle and precision.Figure 1: Potentiometer Basics and Modern ClassificationsⅡ. How are Potentiometers Classified?Potentiometers are primarily classified by their movement mechanism (Linear vs. Rotary) and their control method (Analog Mechanical vs. Digital). Understanding these distinctions is crucial for selecting components for 2026-era PCB designs.Table 1. Industry Standard Potentiometer Classifications (2026)Potentiometer TypeClassification Criteria & Modern StandardsBy Resistor MaterialElectrical performance relies on the track material. Common types include wire wound (high power), synthetic carbon film (consumer audio), metal glass glaze, and conductive plastic (high durability >1M cycles). Specialized types use metal foil or metal oxide film for precision aerospace applications.By Working Environment Selected based on IP ratings and stress factors: High-precision, high-resolution, high-power, or high-temperature variants. Modern sealed potentiometers are essential for automotive and outdoor IoT sensors.By Adjustable ResistanceIncludes fully adjustable (user interface), semi-adjustable (trimpots for calibration), and fine-adjustment types. Non-contact options (Hall Effect, Photo-electric) are gaining market share in 2026 to eliminate mechanical wear and "wiper noise."By Construction MechanicsRotary: Standard rotation is 270°–300°. Multi-turn: Uses a worm gear for 10-20 turns, vital for precision calibration.Linear Slider: Standard in audio mixing consoles for visual feedback of levels (faders). By Gang Number Single Gang: Controls one circuit.Dual/Ganged: Two pots on a single shaft, standard for stereo audio volume control to maintain channel balance.By Resistance Taper (Law)Linear (Type B): Resistance changes proportionally to angle. Used for voltage division.Logarithmic (Type A/Audio): Resistance changes logarithmically to match human hearing. Essential for volume controls.By Actuation MethodManual: Hand-turned knobs or sliders.Motorized: Equipped with a servo motor for remote control and "flying fader" automation in studio consoles. Ⅲ. Detailed Guide: Common Types & ApplicationsSelecting the right potentiometer requires understanding the trade-offs between mechanical endurance, noise levels, and precision.3.1 Breakdown of Key Potentiometer VarietiesRheostat (Variable Resistor)A rheostat functions strictly as a two-terminal variable resistor used to control current. While historically significant, in 2026, the term "rheostat" is considered legacy. Modern efficiency standards prefer PWM (Pulse Width Modulation) for current control over resistive rheostats, which dissipate excess energy as heat. However, they remain useful in simple educational circuits or rugged high-power calibration scenarios. Rotary PotentiometersThe rotary potentiometer is the most ubiquitous interface component. It features a resistive track (Carbon or Cermet) and a wiper connected to a rotating shaft. Key Specs: Typical tolerance is 10%-20%. Rotation is usually 270°. 2026 Applications: Smart home dial interfaces, car audio amplifiers, light dimmers (triac control), and older telecommunication equipment. Logarithmic (Audio) PotentiometersAlso known as "Audio Taper" pots. The resistance changes logarithmically to mirror the Weber-Fechner law of human hearing. At the start of rotation, resistance changes slowly; as the angle increases, the resistance shifts rapidly. This ensures that volume adjustments sound natural and linear to the human ear. Linear Potentiometers (Faders)In linear potentiometers (slide pots), the resistance varies directly with the physical distance the slider moves. They are indispensable in audio mixing consoles (EQ, Faders) because they provide immediate visual feedback of the setting. They are also used for precise voltage division in test equipment and battery internal resistance measurements. Digital Potentiometers (DigiPots)The 2026 Standard: Digital potentiometers are CMOS integrated circuits that replace mechanical wipers with digital switching networks. Controlled via protocols like I2C or SPI, they offer vibration immunity, zero mechanical wear, and programmable precision. Use Cases: Programmable gain amplifiers (PGAs), sensor calibration, LCD contrast control, and smart IoT devices where physical knobs are unnecessary. Membrane (Soft) PotentiometersConstructed by printing carbon/graphite onto a flexible substrate. When pressed, the top layer contacts the bottom resistive track. These are ultra-low profile and widely used in modern wearables, medical devices, and robotics tactile sensors. While they have lower accuracy than wirewound types, their form factor is unmatched for compact designs. Wirewound PotentiometersKnown for high power handling and thermal stability. A resistance wire is wrapped around an insulating core. Pros: High precision, high temperature tolerance. Cons: "Zipper noise" (resolution steps) and inductance issues at high frequencies. 3.2 Critical Application: Potentiometric Position SensorsPotentiometers remain one of the most cost-effective methods for measuring displacement in industrial machinery.3.2.1 Resistive Position SensorsThese function as passive transducers. By applying a stable reference voltage across the fixed terminals, the voltage at the wiper becomes directly proportional to the shaft's angle or linear position. They are widely used in joystick controls, valve positioning, and robotics joint feedback.Figure 2. Simple Position Sensor Circuit 3.2.2 Capacitive Position Sensors (Non-Contact Alternative)For environments where mechanical wear is a concern, capacitive sensors are the superior 2026 choice. They measure position by detecting changes in capacitance between a sensor plate and the target object. These are dominant in high-precision semiconductor manufacturing, touchscreens, and fluid level sensing where physical contact is impossible.Ⅳ. Best Practices: How to Use Potentiometers SafelyTo ensure longevity and signal integrity in your circuits, adhere to these maintenance and installation guidelines:Chemical Safety: Avoid exposing polycarbonate synthetic resin pots to ammonia, ketones, or high-acid chemicals, which degrade the housing.Flux Management: Do not use water-compatible fluxes. Poor quality soldering can lead to oxidation, causing "scratchy" audio or open circuits.Soldering Temp: Prevent heat damage. Pin terminals: 235°C ±5°C. Wire terminals: 350°C ±10°C. Keep solder >1.5mm from the body.Internal Contamination: Ensure no flux enters the internal mechanism during soldering to prevent contact noise.Voltage vs. Current: Potentiometers are designed for Voltage Division. Avoid using them as Rheostats (current limiters) for high loads, as the wiper contact resistance cannot handle high current.Moisture Control: Prevent condensation. In humid environments (like marine audio), use sealed or IP67-rated potentiometers.Mechanical Installation: Do not overtighten mounting nuts. For slide pots, ensure screw length doesn't penetrate the casing and jam the fader.Knob Assembly: Support the back of the shaft when pushing on knobs to prevent internal wiper collapse.Temperature Effects: Lubricant viscosity changes with temperature. For sub-zero applications, specify low-temperature grease to maintain smooth rotation.Signal Interference: Keep shafts/sliders short to minimize acting as an antenna for EMI (Electromagnetic Interference).Thermal Derating: Carbon film power ratings drop above 70°C. Ensure adequate ventilation. Ⅴ. Advanced FAQs and Industry Trends5.1 What are the primary potentiometer types?The industry divides them into Linear (Slide) and Rotary types. A third category, Digital Potentiometers (DigiPots), is now standard for automated systems, while Membrane "Soft Pots" serve ultra-thin form factors.5.2 Quick-Fire FAQsFrequently Asked Questions (2026 Updated)1. What is the main function of a potentiometer?It acts as a variable voltage divider to measure EMF, control volume/gain, or sense position. In 2026, it is also a key component in Human-Machine Interfaces (HMI). 2. What are the top 3 modern applications?User Interface: Volume and tone control in audio gear.Robotics: Position feedback servos (servo motors).Industrial: Linear displacement sensors in injection molding machines. 3. How does a potentiometer differ from a rotary encoder?Potentiometers are absolute position sensors (they know where they are on power-up) but have limited rotation. Encoders are digital, have infinite rotation, but typically require homing (calibration) on startup. 4. Why do audio pots use a logarithmic taper?Because human hearing is non-linear. A logarithmic taper matches the ear's sensitivity, creating a smooth perceived increase in volume.{ "@context": "https://schema.org", "@type": "TechArticle", "headline": "Potentiometer Ultimate Guide 2026: Types, Applications, and Selection", "datePublished": "2020-06-08", "dateModified": "2026-01-09", "description": "A comprehensive engineering guide to Potentiometers in 2026. Covers Linear vs Rotary, Digital Potentiometers, wiring diagrams, and maintenance tips for modern electronics.", "articleBody": "A potentiometer is a three-terminal resistor with a sliding or rotating contact that forms an adjustable voltage divider...", "mainEntity": { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What are the main types of potentiometers?", "acceptedAnswer": { "@type": "Answer", "text": "The three main categories are Rotary Potentiometers (knobs), Linear Potentiometers (sliders/faders), and Digital Potentiometers (DigiPots) which use ICs for control." } }, { "@type": "Question", "name": "What is the difference between a potentiometer and a rheostat?", "acceptedAnswer": { "@type": "Answer", "text": "A potentiometer uses three terminals to divide voltage. A rheostat uses only two terminals (one fixed, one wiper) to restrict current. 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I IntroductionThis article introduces the basics of low voltage transformer, including the definition of low voltage transformer, the principle of low voltage transformer, its installation method, malfunction, and how to repair a household low voltage transformer. A transformer is an electronic instrument that we can use everywhere in our lives. For example, we are inseparable from the mobile phone chargers. The internal components also have transformers. For example, the power supply in our computers is also composed of transformers. Therefore, all electronic products are indispensable for transformers. The transformers used in electronic components are all power transformers (included low voltage transformers). The power transformer is mainly used in electronic products to convert the power supply to the voltage required by the electronic circuit.CatalogⅠIntroductionⅡ Basics of low voltage transformer2.1 Definition of low voltage transformer2.2 Types of low voltage transformers2.3 How does low voltage transformer work?2.4 Design requirements of low voltage transformer2.5 Application environmentⅢ Differences between low&high voltage transformerⅣ How to Estimate the Loss of Low Voltage TransformerV Guide to What You May be Interested in5.1 How to Install Low Voltage Transformer for Household?5.2 How to Troubleshoot a Low-Voltage Transformer5.3 Repairing a household transformer5.4 Malfunction of factory low voltage transformerVI One Question Related to Low Voltage Transformer6.1 Question (Multiple choice questions)6.2 AnswerVII FAQII Basics of Low Voltage Transformer2.1 Definition of Low Voltage Transformer Transformers are important power equipment in our life, especially low-voltage transformer. Whether it is for large-scale power plants or home circuits, it is inseparable from the transformer. There are two kinds of transformers used in our life, one is the high-voltage transformer which used in the high-voltage or ultra-high-voltage circuit, the other is the low-voltage transformer which used in the family lighting circuit or small power circuit.The so-called low-voltage transformer refers to the transformer with low load voltage. As long as the load is lower than 600V, it can be called a low-voltage transformer. The low-voltage transformer is mainly composed of primary coil, secondary coil, and a magnet iron circuit. Low voltage transformers are commonly used for low voltage lighting, which typically only uses 12 or 24 volts. 2.2 Types of Low Voltage TransformersThere are two main types of low voltage transformers: electronic and magnetic.（1）Electronic Low Voltage TransformersElectronic transformers are much smaller, lighter, and less expensive than magnetic counterparts. But they only have about a 5-6 year lifespan. Also, electronic low voltage transformers are known for being noisy.Electronic Low Voltage TransformersAdvantagesDisadvantages▪ Smaller and lighter, easier to hide▪ Less expensive▪ Shorter life span▪ Noisy▪ Heat-sensitive（2）Magnetic Low Voltage TransformersThere are two types of magnetic transformers: stack laminated and toroidal.  Stack laminated transformers have a longer lifespan, about 15 to 20 years. But they only operate at about 80 to 85 percent efficiency, also are known for being noisy.Toroidal transformers are very quiet and more energy efficient. They can operate at about 90 to 95 percent efficiency. And they are long-lived, lasting 20 to 25 years.Magnetic Low Voltage TransformersAdvantagesDisadvantages▪ Long life span of over 15 years▪ Energy efficient▪ Quiet▪ Heavy, big, and difficult to hide▪ Expensive2.3 How Does Low Voltage Transformer Work?Electricity and magnetism are two kinds of energy that can mutually transform. Electricity can generate magnetism, and magnetism can also generate electricity. The low-voltage transformer uses this principle to adjust the voltage through the mutual conversion of electricity and magnetism.A low voltage transformer consists of two electrical coils of wire, one of which is called primary winding and the other is called secondary winding. The primary side of the transformer collects power and the secondary side provides power.Figure 1. Low Voltage Transformer StructureThe two coils intertwine together on a magnet iron circuit core, but without electrically in contact with each other. The magnetic core is made of soft magnetic material, which consists of laminations connected together to help reduce core loss. The core allows power to be transferred from one coil to another. When the primary winding is connected to the power supply, the generated magnetic field transfers the voltage to the secondary winding.Figure 2.  How Does Low Voltage Transformer Work?In summary, the primary winding transforms the electrical power into magnet field when connected to the input voltage supply while secondary winding transforms alternating magnetic field into electrical power of required output.2.4 Design Requirements of Low Voltage TransformerThe low-voltage transformer should be vacuum cast, molded resin encapsulated, 60Hz, Class F insulation, comply with the requirements of IEC726, and meet the requirements of capacity, voltage, phase number, and wiring shown. Each low-voltage transformer has separate primary and secondary windings, and there are two 2.5% normal voltage full-capacity taps above and below the rated voltage on the primary side. The low-voltage transformer should be installed on a base that can isolate, reduce vibration and noise, and the iron core and coil should be properly fixed to withstand the mechanical stress generated in the event of line failure and can withstand 16460 Lite 16460-6 V2. 0 2002/ 11/ 25 Vibration and impact during shipment. Unless otherwise specified, the impedance of low-voltage transformers shall be in accordance with IEC 726. The average noise level of the low-voltage transformer should not exceed the value specified in IEC 726. Each dry-type low-voltage transformer should have appropriate terminals to accommodate the required primary and secondary wiring connections. Low-voltage transformers can be reserved for cable entry from either side or bottom.2.5 Application Environment(1) Ambient air temperature - 5 ℃ to + 40 ℃, 24-houraverage value not more than + 35 ℃(2) The altitude of the installation site shall not exceed 2000m(3) The relative humidity of the atmosphere shall not exceed50% when the ambient air temperature is + 40 ℃(4) A place without violent shaking and impact vibrationIII Differences Between Low&High Voltage Transformer Low Voltage TransformerHigh Voltage Transformerwindingcontinuous windingInterleaved WindingscoolingOil-immersed cooling or air coolingOil-immersed coolingstructureoil tank structurebell jar type oil tankⅣ How to Estimate the Loss of Low Voltage TransformerTransformer loss include copper loss and iron loss. The loss of iron loss is also called no-load loss, and the loss of copper loss is also called load loss. The open circuit of the secondary winding of the transformer applies the no-load current of rated frequency and rated voltage to the primary side, and the active loss caused by the transformer core is called the no-load loss of the transformer. The loss figure can be obtained by the unit loss of the iron core silicon steel sheet multiply the quality of the silicon steel sheet. In general, its loss is very small. For example, the S9-100/10 distribution transformer has a no-load loss of 290W. The larger the transformer capacity, the smaller the no-load loss, generally between 0.3-0.15% of the rated capacity. However, the transformer works continuously for 24 hours, and this loss cannot be ignored. The load loss: The short-circuit of the coil on the secondary side apply the rated current at the rated frequency on the primary side. The transformer loss at this time is the loss of the transformer coil and the iron core. Let's take the S9 series transformer as an example and see its load loss value:The load loss of S9-100/10000 transformer is 1500W.The load loss of S9-1000/10000 transformer is 10300W.The load loss of a transformer is generally between 0.9-1.8%. The larger the transformer, the smaller the load loss.V Guide to What You Maybe Interested in 5.1 How to Install Low Voltage Transformer for Household? First, make sure you have an outlet available. Most family homes will have several outdoor power outlets installed. Second, think about the layout of the lighting. It is important to plan ahead when installing low voltage lighting so that you can avoid any potential problems, especially with the setup.Third, choose a transformer.①Magnetic or Electronic.②Make sure to buy a transformer that can handle the lighting load you need it to.Fourth, install the transformer. Transformers are installed simply by plugging them into your outdoor outlet.5.2 How to Troubleshoot a Low-Voltage Transformer(1) First, check whether there are obvious abnormalities by observing the appearance of the transformer: such as whether the coil lead is broken, whether the insulating material has scorch marks, whether the fastening screw of the iron core is loose, whether the silicon steel sheet is rusted, and whether the winding coil is exposed Wait. (2) Test a transformer with a digital multimeter, open all secondary windings, put the multimeter in the AC block (500mA, in series into the primary winding). When the plug of the primary winding is inserted into the 220V AC mains supply, the multimeter indicates the no-load current value. This value shall not be greater than 10% - 20% of the full load current of the transformer. Generally, the normal no-load current of the power transformer of common electronic equipment should be about 100mA. If too much is exceeded, the transformer has a short-circuit fault. Low Voltage Electronic Transformer Troubleshooting Guide5.3 Repairing a Transformer(1) Understand the reasons for the problem. Generally, a transformer has failed due to some fault in the electrical circuit.(2) Check the replacement transformer. If the short circuit is caused by component failure, the new transformer may still burn out. If you replace the transformer, examine it to make sure that the incident will not occur again.(3) Check the condition of the external fuse. If the transformer has an internal fuse, there may not be a fuse on the power line. On the contrary, the device must be protected by a fuse mounted on the power circuit. Check whether the fuse is intact and replace the faulty fuse.(4) Check the secondary power consumption. Sometimes, this kind of consumption is very high, which leads to equipment failure. If the transformer has multiple ratings and the multimeter shows the value "OL" during the measurement, it may be a short circuit in the secondary winding.5.4 Malfunction of Factory Low Voltage Transformer(1) Abnormal sound in transformerThe abnormal sound inside the transformer may be caused by the following reasons:①Heavy overload causes buzzing sound inside the transformer; ② Due to poor internal contact or breakdown point, the transformer occurs crackle sound③ Some parts of the connection shaft and the core of the transformer are loose, which causes the silicon steel sheet to vibrate④ When there is a grounding or short-circuit fault in the power grid, a large current flows through the winding, which will produce strong noise⑤ The iron core, the winding discharges to the shell, or the core ground wire is disconnected. All these can make the transformer discharge sound. (2) The oil level of the transformer is too high or too lowUnder normal circumstances, the changes in oil temperature can cause a change in oil level. As the oil temperature changes, the oil level also changes accordingly. However, under abnormal conditions, abnormal oil levels can also be caused by faults such as oil seepage and water seepage and other accidents. Second, the change in oil temperature is related to load conditions, ambient temperature and other conditions. When the change of oil level is inconsistent with these elements, it may be a false oil level. (3) Transformer oil quality has deteriorated or oil temperature has suddenly increasedIn working condition, the main function of transformer oil is cooling and insulation. When running overheated for a long time or if water enters the casing and absorbs moisture, the oil quality will deteriorate. Through the oil mark, we can found  that the oil color is abnormally deepened or blackened. Through sampling and analysis, it can be detected that the oil contains carbon particles and moisture, the acid value increases, the flashpoint decreases, and the insulation strength decreases. This situation can easily lead to serious accidents. A sudden rise in oil temperature when the transformer is operating normally is often related to the overheating inside the transformer. The iron core catches fire, the internal screws are loose, the cooling device is faulty, the transformer is heavily overloaded, all may cause the oil temperature to rise suddenly. (4) Transformer on fireWhen the transformer is out of order and it is not handled in time, it may catch fire. When the transformer is on fire, the insulating oil burns and turns into gas, which makes the oil tank burst. The burning insulating oil sprays out of the transformer, which will cause equipment damage and property loss. The short circuit inside or outside the transformer wire, severe overload, a lightning strike may cause the transformer to catch fire.VI One Question Related to Low Voltage Transformer6.1 Question (Multiple choice questions)The winding of wire around a core which is connected to a source of energy is called the ______ coil.primarysecondarytertiary6.2 AnswerA、B  VII FAQ1. What are low voltage transformers?A low voltage transformer is at the heart of every landscape lighting system. It converts 120-volt current to a low voltage current (between 12-15 VAC). ... Magnetic transformers use two coils to reduce the voltage from 120 volts down to 12 volts. 2. What low voltage transformer do I need?Transformers generally range from 150- to 900-watt capacity. Matching the size of the transformer to the lighting design is important for the efficient operation and function of the system. House current, 120 volts, is reduced by a transformer to 12 to 20 volts, the current needed to operate low-voltage landscaping lights. 3. What are low voltage transformers used for?Low Voltage Transformers Low voltage transformers are power transformers that are used to change the voltage capacity of a low-voltage electrical transmission line. Typically, electronic low voltage transformers convert 120 volts into 12 volts or 24 volts. 4. How do you test a low voltage transformer?• Identify the transformer's terminals, using its label as a guide. • Turn a multimeter to its VAC function. • Test the transformer's input voltage with the multimeter, using the transformer's label as a terminal guide. • Test the transformer's output voltage with the multimeter. 5. How long do low voltage transformers last?20 to 25 years.They operate at about 90 to 95 percent efficiency and can run for a very long time, anywhere from 20 to 25 years. They also are much quieter, so you can place them close to the fixtures, rather than having to run wires a long way from the transformer to the fixture itself. 6. Can I plug a low voltage transformer into an extension cord?One warning though to be observed is to never use an extension cord between the transformer and the electrical outlet. Always plug the transformer directly into the power outlet. As you can see, low voltage outdoor lighting is not all that hard to install or maintain. 7. Can you hardwire a low voltage transformer?To hardwire a low voltage transformer, the main power should be turned off at the breaker panel before making any electrical connections. ... The polarity of these wires is not important; either wire on the output side of the transformer may be connected to either wire of the low voltage circuit. 8. Do you need a transformer for low voltage lighting?When operating low voltage lights, you need a transformer to convert your standard line voltage (120V or 277V) into low voltage (12V or 24V). This allows your lights to function properly. If you connect low voltage lights directly to line power, the higher voltage would cause them to burn out immediately. 9. How do you tell if a transformer is going bad?Symptoms of power quality issues include vibration, excessive buzzing or humming and overheating. Technicians should occasionally check the power of transformers that supply nonlinear loads, such as variable frequency drives (VFDs) or switching power supplies. 10. Can you replace a transformer with a light fitting?They will have a transformer either in the ceiling or light fitting. Some LED bulbs, like the Philips Master LED range, have in-built circuitry that can deal with most (but not all) transformers, so you don't have to change them. In other cases, you need to replace the transformer with an LED driver. 

Ⅰ. IntroductionIn electronics, an operational amplifier is a circuit unit with a very high amplification factor. In the actual circuit, usually combined with the feedback network to form a certain functional module. It is an electronic device with a special coupling circuit and feedback. The output signal can be the result of mathematical operations such as addition, subtraction or differentiation, integration, etc, thus it was used in analog computers to implement mathematical operations.CatalogⅠ. IntroductionⅡ. Non-inverting Amplifiers and Inverting Amplifiers   2.1 Terminology   2.2 Non-inverting Amplifier Circuit   2.3 Inverting Amplifier CircuitⅢ. Note: Input ImpedanceⅣ. Amplifier GainⅤ. Differences between Inverting & Non-Inverting Amplifiers   5.1 Facts Consideration   5.2 Differences SummaryⅥ One Question Related to Amplifier and Going Further   6.1 Question   6.2 AnswerAn op amp is a functional unit that can be implemented in discrete devices or in semiconductor chips. With the development of semiconductor technology, most of the op amps exist in the form of a single chip, but there are many types of op amps, which are widely used in the electronics industry. The op amp can be simply viewed as a high-gain direct-coupled voltage amplifying unit with one signal output port (Out) and two high-impedance inputs, non-inverting input and inverting input, so op amps can be used to make the non-inverting, inverting, and differential amplifiers.Difference between Inverting and Noninverting Amplifier Ⅱ. Non-inverting Amplifiers and Inverting Amplifiers2.1 TerminologyAn operational amplifier in an electronic circuit has a non-inverting input and an inverting input. The same polarity of the input and the output is a non-inverting amplifier, on the contrary, it is an inverting amplifier. And the inverting amplifier circuit has a function of amplifying the input signal and inverting the output. 2.2 Non-inverting Amplifier CircuitWhen a positive phase is received, a positive phase is output, whereas the negative phase is output. The phases of non-inverting end and the output end are the same. In other words, the signal is applied to the non-inverting input of the op-amp, and it is not inverted at the output when compared to the input. Figure 1. Non-inverting Amplifier(A signal applied keeps its polarity at the output, and a positive input remains a positive output.)Vin and V-Virtual are short circuit in the figure, where Vin=V-……aBecause of the virtual open circuit, there is no current to the inverting input, the current through R1 and R2 is equal, and the current is set to I, which is obtained by Ohm's law:I=Vout/(R1+R2)……bVin equal to the partial voltage on R2, where Vin=I*R2……cBy a, b, c, where Vout=Vin*(R1+R2)/R2 2.3 Inverting Amplifier CircuitWhen the positive phase is received, the negative phase is output, whereas the positive phase is output. And the non-inverting end and the output end are keeping inverting relation. An inverting amplifier provides the same function as the common emitter and common-source amplifier.Figure 2: The grounding of the op amp is 0V, the inverting end and the non-inverting end are short circuit, so it is also 0V. The input resistance of the inverting input is very high, while it is virtual open. So that there is almost no current injection and outflow, then R1 and R2 are equal to a series connection, the current flowing through each of the components in a series circuit is the same, that is, the current flowing through R1 and the current flowing through R2 are the same. Figure 2. Inverting Amplifier(The polarity of a signal is reversed at the output, and a negative input becomes a positive output.)Current flowing through R1: I1=(Vin-V-)/R1………aCurrent flowing through R2: I2=(V--Vout)/R2……bV-=V+=0………………cI1=I2……………………dBy solving the above algebra equation, we can get the result:Vout=(-R2/R1)*ViThe inverting amplifier circuit has the function of amplifying the input signal and inverting output, which is a negative feedback technique. Negative feedback returns a portion of the output signal to the input. The reason why the inverting amplifier can only connect the signal to the inverting input is because the negative feedback can be formed only in this way, otherwise it will not work in the linear amplification region.When inputting from both ends simultaneously, the size and phase are the same, that is the common mode signal, and the theoretical output is zero. Ⅲ. Note:  Input ImpedanceThe input impedance of the non-inverting input is high, and the input impedance of the inverting input is low. The input impedance of the non-inverting input is basically determined by the bias resistor connected in parallel with the non-inverting terminal, and the resistance can be very large. When the inverting input is connected, the feedback resistor is connected between the inverting terminal and the output terminal, and the resistance is small, so the input impedance of the inverting input is relatively low.1. The magnitude of the input resistance of the non-inverting amplifier does not affect the input impedance, and the inverting amplifier input resistance is approximately equal to the input impedance.2. When the input impedance is required to be high, the non-inverting amplifier should be selected.3. If the input impedance is not required to be large, the non-inverting or inverting can be selected at this time. When the phase is not considered strictly, the inverting amplification is preferred because it only has the differential mode signal.4. The CMRR of the inverting amplifier is better when the CMRR is decisive.Inverting amplifier, the input common mode of the op amp is almost constant, the common mode amplification is not reflected to the output, and the input common mode of the op amp in the non-inverting amplifier changes with the input signal, the common mode amplification of the op amp will be reflected Output. Therefore, the CMRR of the inverting amplifier is better when the CMRR of the op amp is decisive. Ⅳ. Amplifier GainBasic Inverting Amplifier Made with an Op-ampNon-inverting AmplifierInverting AmplifierGAIN (AV) = 1+(R2 / R1)Example:if R2 is 1000 kilo-ohm and R1 is 100 kilo-ohm the gain would be :1+ (1000/100) = 1 + 10 or GAIN (AV) = 11If the input voltage is 0.5v the output voltage would be : 0.5 X 11 = 5.5vGAIN (AV) = -R2 / R1Example:if R2 is 100 kilo-ohm and R1 is 10 kilo-ohm the gain would be :-100 / 10 = -10 (Gain AV)If the input voltage is 0.5v the output voltage would be : 0.5v X -10 = -5v Ⅴ. Differences between Inverting & Non-Inverting Amplifiers5.1 Facts ConsiderationIt can be seen that comparing them is from the following aspects: input and output impedance, common mode anti-interference.1. The input impedance of the non-inverting amplifier is equal to the input impedance of the op amp, and they are close to infinity. The input resistance of the non-inverting amplifier does not affect the input impedance; and the input impedance of the inverting amplifier is equal to the resistance of the series resistor of the signal to the input. Therefore, when the input impedance is required to be high, the non-inverting amplifier should be selected.2. The input signal range of the non-inverting amplifier is limited by the op amp's common-mode input voltage range, while it is not the case with the inverting amplifier. Therefore, if the input impedance is required to be low and the phase is free, the inverting amplification is preferred because it only has a differential mode signal. And the anti-interference ability is strong, thus a larger input signal range can be obtained.3. In the design where the same magnification is required, try to select a resistor with a small value, which can reduce the influence of the input bias current and the influence of the distributed capacitance. If you are more concerned about power consumption, you have to compromise on the resistance.4. Determine if an input signal is a non-inverting input or an inverting input. If the input resistance of the amplifier circuit is required to be large, the non-inverting input amplifier circuit should be used because the increase of the input resistance of the amplifier circuit will affect the voltage gain. When the inverting input resistance is increased, the voltage gain of the circuit is reduced, and the voltage gain is also affected by the internal resistance of the signal source. Therefore, when designing the inverting input amplifying circuit, sometimes the input resistance and the voltage gain is difficult to balance. If the bias resistor or the voltage divider is appropriately increased, the input resistance of the amplifier circuit can be increased, and the voltage gain has little or no effect on the voltage gain, which requires a better understanding of the circuit.Figure 3. Integrated Circuit Using Op-amp5.2 Differences SummaryThe integrated amplifier can be connected to the non-inverting or to the inverting amplifier. Is it better to select non-inverting amplification or inverting amplification? Let's look at the difference between them.1）non-inverting amplifiera. AdvantagesThe input impedance is equal to the input impedance of the op amp, which close to infinity.b. DisadvantagesThe amplifying circuit has no virtual ground, so it has a large common mode voltage, and the anti-interference ability is relatively poor. So that the op amp requires a higher common mode rejection ratio, and another disadvantage is that the amplification factor can only be greater than one.2）inverting amplifiera. Advantages The potential of the two input terminals is always approximately zero (the non-inverting terminal is grounded, and the inverting terminal is virtual-grounded), in addition, only the differential mode signal exists, and the device has strong anti-interference ability.b. Disadvantages The input impedance is small, which is equal to the resistance of the series resistance of the signal to the input.3) The gain calculation of the two are different, and their phases are opposite. Ⅵ One Question Related to Amplifier and Going Further6.1 QuestionWhat are non-inverting amplifiers used for?6.2 AnswerThe non-inverting amplifier configuration is one of the most popular and widely used forms of op amp circuit and it is used in many electronic devices. The op amp non-inverting amplifying circuit provides a high input impedance along with all the advantages gained from using an op amp. Frequently Asked Questions about Difference between Inverting and Noninverting Op Amp1. Which is better inverting or noninverting amplifier?Inverting op-amps provide more stability to the system than non-inverting op-amp.In case of inverting op-amp negative feedback is used that is always desirable for a stable system. 2. What are the advantages of non inverting amplifier over inverting amplifier?The advantages of the non-inverting amplifier are as follows: The output signal is obtained without phase inversion. In comparison to the impedance value of the input at the inverting amplifier is high in the non-inverting amplifier. The voltage gain in this amplifier is variable. 3. What is an inverting amplifier used for?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it. 4. Where are non-inverting amplifiers used?The non-inverting amplifier configuration is one of the most popular and widely used forms of operational amplifier circuit and it is used in many electronic devices. The op amp non-inverting amplifier circuit provides a high input impedance along with all the advantages gained from using an operational amplifier. 5. Why are inverting amplifiers better than non inverting?Inverting op-amps provide more stability to the system than non-inverting op-amp.In case of inverting op-amp negative feedback is used that is always desirable for a stable system.

Regarding the design of a micropower isolated power supply for the two-wire transmitter, we must know what is the transmitter first. When the output of the sensor is a specified standard signal, it is called a transmitter. A sensor, usually composed of sensitive elements and conversion elements, is a floorboard for a component or device that can be measured and converted into a usable output signal according to certain rules. And the common types are power transmitters, current-voltage transmitters, and so on.How to Build a FM Radio Transmitter CatalogI. Brief Introduction to Internal Micro-power Supply DesignII. Overall DesignIII. Constant Current Voltage Stabilizing CircuitIV. DC/CD in CircuitV. Isolated Power Source WindingVI. ConclusionFAQ I. Brief Introduction to Internal Micro-power Supply Design The design of an internal micro-power supply is very important when developing a low-power intelligent two-wire transmitter. Firstly, in order to satisfy the power supply of the micro-controller, A/D, D/A, and communication circuit, the intelligent transmitter with microprocessor needs more power than that of an ordinary 4~20mA one), and its power supply efficiency of the internal power supply must be higher.  In addition, for capacitive sensors and thermocouples, it is necessary to consider the case of grounding or the possibility of the sensor earthing. So the input and output of the designed transmitter circuit must be isolated, only this way can guarantee the normal operation of the follow-up control system and the ability of anti-common-mode interference.  Since the external circuit provides the maximum working current of 4mA for the two-wire transmitter system, specific requirements like this bring great difficulties and challenges to the design of the power supply of the system. Adopting a full integrated circuit, the isolated two-wire transmitter power supply with micro-input power has the advantages of simple structure, stable performance, and low cost. And it takes the 12~35V DC as the input power, designing the simple input circuit of the constant current and stable voltage front end, fixing the consumption of 315mA current, and providing two sets of isolated 3V power supply. In this case, the not isolated imputing group with maximum 5mA load capacity and the isolated imputing group with maximum 3mA load capacity, which can meet the requirements of input and output isolating two-wire transmitters for power supply.  II. Overall Design Fig.1 is a schematic diagram of the power supply. It consists of three main parts: 315mA/812V constant current voltage stabilizing circuit composed of U1, R1, and Z1; DC/DC converter circuit composed of U2 as the core; and a set of isolated power supply composed of L2 and U3. The system is designed to be concise and highly integrated, and all selected components can work at -40 ~ 85 ℃, which can ensure the reliable application of the power supply to field transmitters.Fig.1 Schematic Diagram of Power Supply III. Constant Current Voltage Stabilizing Circuit As a power supply to the two-wire transmitter, the maximum working current is 4mA. The transmitter with this power supply needs some low zero output indication, so the general system power supply standard is usually below 315mA, meanwhile, this type of power supply must have constant current characteristics to meet the operating requirements of the two-wire transmitter. And there are many ways to design constant-current sources. The design in Fig.2 adopts the three-terminal adjustable voltage stabilizer LM317L to design a constant-current source. LM317L is a three-terminal adjustable voltage stabilizer, and its application is as follows in Fig.2. Its basic application as a standard regulator is shown in Fig.2 (a), where a steady pressure difference is generated between the output and adjustment terminal, the typical value is 1125V, so its output voltage is VO=1125 (1+Ra/Rb). Because of the stable pressure difference of LM317, it is often used to design the constant-current source. Fig.2 (b) is a typical application circuit, which generates a current of I=1125 / R, consulting Fig.1; the R1 value in the design is 360Ω, so you can obtain a constant current of about 315mA.  Considering the working voltage range of the subsequent DC/DC chip is 4~11V and the actual out the power supply, a voltage stabilizer Z1 with 812V is used to parallel the voltage stabilizing function while providing a stable inlet voltage for U2. It requires that the U2 total current consumption is less than 314mA and Z1 must be the high-quality voltage stabilizer with the breakdown current less than 011mA (Philips products can be used, the lowest static stable current is only dozens of μA). Fig.2 Typical Application of LM317LThe D1 of the front end of the circuit is an anti-inversion diode( as shown in Fig.1), generally using 1N4148. The fuse is the PTC device self-recovery fuse, its parameter is 100mA/ 60V, which ensures that the external power supply will not be affected when the power supply fails. The field transmitter is the final application of the power supply. Its changing ambient temperature is in a wide range, so the temperature drift must be taken into account. The main temperature drift of the power supply is the constant current drift, which is caused by the temperature drift of the reference voltage difference of LM317L and the temperature drift of the constant current resistance R1. In reality, the temperature drift can be neglected when the temperature coefficient is below 5*10-6/℃.  The relationship between the reference pressure difference and temperature coefficient of LM317L is shown in Fig.3: The temperature effect is obvious in the temperature range of - 40-85%, thus compensation must be made in the high precision application. In intelligent transmitter systems, in order to correct sensors and compensate circuits, temperature sensors are commonly designed in the transmitter circuits, because the practical applications of power supply are aimed at intelligent transmitters. But the digital thermometric chip, like LM75 or TC77, does not design a special hardware compensation, while a software compensation algorithm provided when applying power supply to deal with temperature drift.  Fig.3 LM317L Benchmark Temperature CurveAs shown in Fig.3, the curve of the relationship between the reference pressure difference and temperature of LM317L is approximate to a simple cubic polynomial function. It only needs to design a compensation function for the reverse Y-axis, and the system is calibrated at 20 ℃ as the basic compensation. The specific compensation formula is ΔI=A (t-20)2+B (t-20) in which “t” is the ambient temperature. The coefficients A and B can be derived from the reference voltage temperature curve provided by the LM317L chip manual, the simplest method is to obtain two binary linear equation groups for solving A and B by taking two points of -20 ℃ and 60 ℃. In this way, it is easy to obtain an approximate function of the compensation curve with a good fitting degree, and the effect of compensated temperature drift can be neglected basically. The biggest difficulty of power supply design is that the input power is very small, thus the isolated feedback mode with high power consumption should be avoided in the design of the isolation terminal, and the open-loop auxiliary side should be used in the actual circuit. The specific process is using MAX639 to design the core circuit of DC/DC, which realizes the high power efficiency conversion. For example, when the input of 315mA is supplied, it can supply the circuit with a current much larger than that of 315mA, thus solving the need for a large current in an intelligent system. According to the requirements of the system, the core chip must have the advantages of low power consumption, high efficiency, wide input voltage range, and simple peripheral devices. The DC/DC chip in Fig.1 is MAXIM's MAX639, which is a step-down converter chip. Its main features are wide input voltage range (4~115V), high conversion efficiency (up to 90%) and low static current (10 μ A); fixed output or an adjustable output. IV. DC/CD in Circuit The circuit is designed for adjustable output and the output is set to 3V. Output current: Io=（Vi Ii η）/Vo, Vi is the input voltage; Ii is the input current, and η is the conversion efficiency and Vo is the output voltage. In the circuit, Vi=812V, Ii=315mA,η= 90%, Vo=3V, getting an approximation Io=816mA without considering the isolating side output, this output current is already a relatively large supply capacity in the low-power system. But the calculation of the above Io is only theoretical, if you want to make the circuit operate reliably under the condition of micro-input power such as 315mA/812V, and to obtain more than 90% conversion efficiency, it is necessary to design the circuit very carefully. The reliable operation of DC/DC is restricted by many conditions, the necessary condition is providing sufficient start-up pulse current. A 10μF tantalum electrolytic capacitor C2 in parallel to Z1 provides an operation guarantee, also it can effectively avoid the interference of DC/DC work on the constant current of LM317. The inductance L1 plays a decisive role in the conversion efficiency of DC/DC. The algorithm provided by the MAXIM manual is L1=50/I0, μH is the unit of L1 and A is the unit of I0. In the practical circuit, the value of L1 is 4mH, which can ensure the circuit work stably under the maximum output power, and it can keep the high conversion efficiency at the same time. what should be emphasized is that if L1 is small, the conversion efficiency of the circuit will be reduced, the starting current will increase and even can not operate. If L1 is larger, the output capacity will decrease and the DC/DC circuit will oscillate. To ensure the stability of the circuit, DC / DC chip has a high requirement for output capacitor C3, the most important is that its equivalent series resistance ESR must be smaller, and it must have enough capacity at the same time. So a 10μF tantalum electrolytic capacitor with excellent performance is used in the circuit design, which can guarantee a stable output. The DC/DC chip is the core of the circuit, and the actual circuit layout has a great influence on the performance of the circuit, especially on the output ripple. The unreasonable layout design of the circuit board will even bring extra parasitic oscillation in the output, so much more attention should be paid to the design. Thus the most important principle is that the ends of C2 and LI lead should be as close as possible to the MAX639 pin, and the grounding pins of C2, D2, MAX639, R3, and C3 should be as close as possible to each other, linking with thick wires. The setting input voltage of DC/DC is 812V, which is guaranteed by Z1. If the actual transmitter requires a lower power supply, Z1 can choose a lower stable voltage, which makes the whole power supply require a lower input voltage. The low threshold of the inlet voltage is 12V; if Z1 selects 612V, the threshold voltage can be reduced to 10V. V. Isolated Power Source Winding The main feature of the circuit is to provide an isolated power supply winding, which uses the method of "stealing" electricity on the DC/DC output energy storage inductor. In Fig.1, the L2 is the power supply coil for this isolated power supply. Because the isolating power supply is a secondary coil loaded on the energy storage coil of DC/DC, and its structure is an open loop, therefore its output stability is relatively poor. In order to obtain satisfactory results, it is necessary to consider the whole design from different angles.First of all: determine its output power. Because of the method of "stealing" electricity from the energy storage coil, its output power is limited and can only be smaller than the original side output power. The output of this set of isolated power supply is mainly supplied by sensor conversion circuit, front-end A/D converter, and isolated circuit in the application of specific transmitters. And the power consumption of analog measuring circuits of differential capacitance sensors, thermocouple sensors, and thermal resistance sensors reaches μA level. The front-end A/D is usually multi-integral or Σ-Δ, the power consumption is less than 1 mA, and the whole low power dissipation optoelectronic isolation can be below 1mA. Therefore, isolated windings provide 3mA that can meet the actual needs. It has been calculated that the maximum output of the circuit is 816mA without the secondary winding, so it is obvious that the 3mA current can be supplied in the case of the secondary winding. Secondly: Avoid working / hibernating rotation for devices with high power consumption. The isolation winding adopts an open-loop structure, and the change of load on the primary side directly affects the stability of the secondary side, so it is required that the power consumption stability of the original circuit system should be guaranteed as much as possible when the circuit is used in practice. What’s more, the circuit can provide the maximum 5mA current for the original edge and can fully meet the requirements of the commonly used low-power MCU control system without the use of sleep mode. In this way, the maximum system running speed can be obtained. Finally:  the low-voltage difference linear regulator and the DC/DC converter should be used in the design. The isolated power winding mainly supplies power to the front-end small-signal analog circuit, therefore, the quality of the power supply requires high. Noise reduction and voltage stabilization treatment of low voltage output converted by DC/DC through low dropout linear regulator(LDO), which can not only improve the efficiency of power supply but also meet the requirement of small ripple voltage. Specifically, LDO uses MAX1726 chip, its working current is the only 2μA, the output is 313V; The output amplitude before voltage stabilization depends on the output power of the original edge and the inductance of L2, the experiment confirmed that L2 is 3mH. When the primary current varies between 3~5mA and the secondary current is 2mA, the voltage fluctuates between 318V and 418V before the voltage stabilizes, which meets the input requirements of the LDO voltage stabilizer. VI. Conclusion The isolated power supply of two-wire transmitter is stable and reliable, and can meet various complex requirements of the use of two-wire transmitter. It has the characteristics of wide temperature range, wide input voltage range, high output efficiency, high integration, good isolation performance, small volume and low cost. And this power supply has been applied to the integrated intelligent temperature transmitter, after a long period of field test, finding that it has excellent performance and can fulfill the requirements of the isolated two-wire transmitter completely. FAQ 1. What does a transmitter do?In the Telecommunications world, a Transmitter is a device that produces radio waves radiating from an antenna. In the world of process control, a Transmitter is a device that converts the signal produced by a sensor into a standard instrumentation signal representing a process variable being measured and controlled. 2. What is called transmitter?In electronics and telecommunications a transmitter or radio transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. 3. What is transmitter and its types?Pressure transmitters are divided into three types: Absolute Transmitter: This transmitter take vacuum pressure as its base, and then measures process pressure. Gauge Transmitter: This type measures process pressure with the location's atmospheric pressure as a base. 4. What are the main features of transmitter?Some of the main features which make the transmitter complex are higher clock speed, higher transmit power, directional antennas and need for a linear amplifier. 5. What is transmitter frequency?A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. 6. What is the difference between transmitter and antenna?A transmitter is a different kind of antenna that does the opposite job to a receiver: it turns electrical signals into radio waves so they can travel sometimes thousands of kilometers around the Earth or even into space and back. Antennas and transmitters are the key to virtually all forms of modern telecommunication. 7. What is difference between transmitter and transducer? Transducers and transmitters are virtually the same thing, the main difference being the kind of electrical signal each sends. A transducer sends a signal in volts (V) or millivolt (mV) and a transmitter sends a signal in milliamps (mA). 8. What is transmitter PLC?Transmitters are also referred to as stationary instruments and convert measurement parameters into an electrical signal that is then sent to a BMS ( Building Management System), PLC ( Programmable Logic Controller), SCADA ( Supervisory Control and Data Acquisition). 9. What is the pressure transmitter?A Pressure Transmitter is an instrument connected to a Pressure Transducer. The output of a Pressure Transmitter is an analog electrical voltage or a current signal representing 0 to 100% of the pressure range sensed by the transducer. 10. Which oscillator is used in transmitter?Crystal oscillators are the most common type of linear oscillator, used to stabilize the frequency of most radio transmitters, and to generate the clock signal in computers and quartz clocks. You May Also LikeThe 3W PowerSpot transmitter for Power Over-the-air from PowercastBuild a Remote RC Firecracker and Firework lgniter Using RF Transmitter4 Channel 2 Core Twisted Pair Remote Controller Using PT2262