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crwdns2936043:0crwdne2936043:0 crwdns2933505:0crwdne2933505:0 Arthur Shi
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| [title] Capacitor basics | |
| [* icon_note] A capacitor is a component that stores electrical energy. It's like a low capacity, fast charging battery—except a battery stores energy via an electrochemical process, whereas capacitors store energy via electrical fields. | |
| [* icon_note] Capacitors are often used to store bursts of energy and filter/smooth out voltage fluctuations. Most circuit boards will have tiny surface-mount capacitors, while power supplies will have bigger cylindrical ones. | |
| [* icon_caution] Thumb-sized capacitors can store enough energy to pose a risk of electric shock. [guide|2177|Use a capacitor discharge tool|new_window=true] to safely discharge larger capacitors. | |
| [* icon_note] Capacitance is a measurement of how much a capacitor can store at a given voltage. The SI unit of measurement for capacitance is a ***Farad (F)***. Most capacitors have a nF (nanofarad) or μF (microfarad) capacity. | |
| [* icon_note] Larger capacitors such as electrolytic capacitors are ''polarized'', meaning they should only be connected in a specific direction. If they're used in reverse for extended periods of time, they will fail and often burst. | |
| - | [* icon_note] When a capacitor fails, it usually short-circuits. The dielectric material which insulates the layers breaks down and the layers conduct, shorting the capacitor. ***A working capacitor should never have a resistance measurement of less than a few |
| + | [* icon_note] When a capacitor fails, it usually short-circuits. The dielectric material which insulates the layers breaks down and the layers conduct, shorting the capacitor. ***A working capacitor should never have a resistance measurement of less than a few kilohms.*** |
| [* icon_note] The multimeter measures capacitance by charging the capacitor with constant current, recording how long it takes for the capacitor to charge/discharge, and calculating the capacitance value with [link|https://en.wikipedia.org/wiki/Capacitor#Current%E2%80%93voltage_relation|an equation|new_window=true]. Depending on the size of the capacitor, the multimeter [[How to Use Your iFixit CM-D20 Digital Multimeter#Section_Accuracy_Specifications|may not give a very accurate reading|new_window=true]]. | |
| [* icon_note] ***You'll often need to decouple the capacitor from the circuit in order to measure it.*** Capacitors are commonly integrated in parallel to other components in a circuit, making direct measurement difficult. To decouple the capacitor, desolder/disconnect one end of the capacitor from the circuit. |