The thing is, a charged capacitor left by itself will retain this charge for a long time, even years. When a capacitor is disconnected, the instant voltage it carries is maintained across the previously connected terminals, which can be dangerous. All capacitors have leakage so we can imagine that we have a very high-resistance mega ohm resistor parallel to the capacitor.
When the capacitor is disconnected, the voltage will be discharged via this imaginary resistor. This is what causes the gradual discharge. However, every capacitor has a different capacitance and will need a different time period to fully discharge. Not to mention, things can always go wrong even in smaller capacitors and these charges would remain in the capacitors. Before we can discuss how to safely discharge a capacitor, we have to first understand how a capacitor works. Ralph received his B.
There are 15 references cited in this article, which can be found at the bottom of the page. This article has been viewed , times. Capacitors are found in a number of electrical appliances and pieces of electronic equipment. They store excess electrical energy during power surges and discharge it during power lulls to provide the appliance with a constant, even supply of electricity.
Before working on an appliance or electronic device, you must first discharge its capacitor. Start by checking for a charge in your capacitor, then choose a method to discharge it if needed. To discharge a capacitor, it's important that you keep your hands clear of the terminals at all times or you could get badly shocked. Also, make sure you're using an insulated screwdriver that has no signs of damage on the handle.
When you're ready, start by gripping the capacitor low on the base with one hand. Then, lay the screwdriver across both terminals to discharge the capacitor. To test if the capacitor discharged properly, touch both terminals at the same time with the screwdriver again. If there's no spark, the capacitor is discharged. To learn how to make and use a capacitor discharge tool, scroll down! Did this summary help you? Yes No. Log in Social login does not work in incognito and private browsers.
Please log in with your username or email to continue. No account yet? Create an account. Edit this Article. We use cookies to make wikiHow great. By using our site, you agree to our cookie policy.
Cookie Settings. Learn why people trust wikiHow. Download Article Explore this Article parts. Tips and Warnings. Things You'll Need. Related Articles. Article Summary. Part 1. Disconnect the capacitor from its power source. This usually means unplugging the electronic device from the wall outlet or disconnecting the battery in your car. Slide the cable off of the terminal to disconnect it. Set your multimeter to its highest DC voltage setting. The value entered into the field is too short.
Your web browser is no longer supported, download a new version. This Website is using cookies. Click here to find out more about cookies and their settings. You are browsing international version of the website. Select country and language The selected country and language determine your trading conditions, product prices and special offers Country Albania.
American Minor Outlying Islands. American Samoa. American Virgin Islands. Antigua and Barbuda. Bonaire, Saint Eustatius and Saba.
Bosnia and Herzegovina. British Indian Ocean Territory. British Virgin Islands. Brunei Darussalam. Burkina Faso.
Cape Verde. Cayman Islands. Central African Republic. Christmas Islnd. Coconut Islands. Cook Islands. Costa Rica. Czech Republic. Dominican Republic. East Timor. El Salvador. Equatorial Guinea. Falkland Islands. Faroe Islands. French Guyana. French Polynesia. Hong Kong. Marshall Islands. New Caledonia. New Zealand. Norfolk Islands. North Mariana Islands. Papua New Guinea. Pitcairn Islands.
Puerto Rico. Republic of North Macedonia. Russian Federation. Saint Helena. Real as opposed to ideal capacitor has leakage resistance. It can be viewed as a large resistance in parallel with capacitor. There is a leakage current, which could be on the order of 1uA in large electrolytic capacitors.
Short it out for a few seconds On large electrolytic caps, like "main-frame" computer grade ,uF and TV HV 10uF 25KV doubler Caps, power supplies there is a phenomena like in batteries, known as memory.
After you short it out the voltage creeps back. That's all you need to know. Short it long enough to discharge the memory effect. Actually the capacitor has a few more non-ideal characteristics that can be put into the schematic.
So the rest of this is for educational, technical, and factual values. In fact some of my grey beard colleagues will remember that caps in storage like this required slow "conditioning" to prevent puncturing the insulation inside so a slow charge up for an hour was recommended before use. Thats the C2 cap physical property. It can short out.
This Memory capacitance C2 may be the smaller or much higher so the original voltage is restore but the series resistance R3 is enough so you cant get much current from it but it can give you a jolt if you only short the cap for a zap or split second.
Monolithic caps are almost uncommon these days but bigger, more reliable but these days multi-layer metallized caps are most common. The most ideal caps in electronics are also the most expensive. I am referring to plastic Caps Teflon then Polyurethane, Mylar. Mylar were default used in old telephones If you want a time constant in minutes or maybe hours in some cases, that is possible. There a dozens of other materials including silver mica, and a few more exotic materials.
I recommend shorting out C1 and count to 5 seconds, but dont take my word, zap one and then measure it.. The resulting voltage indicates the Cap Ratio. You will not likely find simulators use my schematic, but it is accurate. There are some variations and you can neglect most of them if you use it within guidelines of the component.
Capacitors will lose their charge over time, and especially aluminium electrolyts do have some leakage. Nevertheless, YMMV, and you will see capacitors which can hold their charge for several months. It's wise to discharge them. Don't short-circuit them right away, they don't like that.
0コメント