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| [title] Capacitor basics | |
| [* icon_note] A capacitor is a device 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 kiloohms.*** | |
| - | [* icon_note] The multimeter "measures" capacitance by charging the capacitor with |
| + | [* icon_note] The multimeter "measures" capacitance by charging the capacitor with current, recording the voltage decay as the capacitor discharges, and calculating the capacitance value with an equation. 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. |