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id="toc-Ships'_hulls-sublist" class="vector-toc-list"> <li id="toc-Degaussing_range" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Degaussing_range"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Degaussing range</span> </div> </a> <ul id="toc-Degaussing_range-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-High-temperature_superconductivity" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#High-temperature_superconductivity"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>High-temperature superconductivity</span> </div> </a> <ul id="toc-High-temperature_superconductivity-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Early_experiments" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Early_experiments"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Early experiments</span> </div> </a> <ul id="toc-Early_experiments-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Color_cathode-ray_tubes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Color_cathode-ray_tubes"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Color cathode-ray tubes</span> </div> </a> <ul id="toc-Color_cathode-ray_tubes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Magnetic_data_storage_media" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Magnetic_data_storage_media"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Magnetic data storage media</span> </div> </a> <button aria-controls="toc-Magnetic_data_storage_media-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Magnetic data storage media subsection</span> </button> <ul id="toc-Magnetic_data_storage_media-sublist" class="vector-toc-list"> <li id="toc-Irreversible_damage_to_some_media_types" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Irreversible_damage_to_some_media_types"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Irreversible damage to some media types</span> </div> </a> <ul id="toc-Irreversible_damage_to_some_media_types-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Tape_recorders" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Tape_recorders"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Tape recorders</span> </div> </a> <ul id="toc-Tape_recorders-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Types_of_degaussers" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Types_of_degaussers"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Types of degaussers</span> </div> </a> <button aria-controls="toc-Types_of_degaussers-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Types of degaussers subsection</span> </button> <ul id="toc-Types_of_degaussers-sublist" class="vector-toc-list"> <li id="toc-Electromagnetic_degaussers" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Electromagnetic_degaussers"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Electromagnetic degaussers</span> </div> </a> <ul id="toc-Electromagnetic_degaussers-sublist" class="vector-toc-list"> <li id="toc-Rotating_coil_degausser" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Rotating_coil_degausser"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.1</span> <span>Rotating coil degausser</span> </div> </a> <ul id="toc-Rotating_coil_degausser-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Pulse_degaussing" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Pulse_degaussing"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1.2</span> <span>Pulse degaussing</span> </div> </a> <ul id="toc-Pulse_degaussing-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Permanent_magnet_degausser" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Permanent_magnet_degausser"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Permanent magnet degausser</span> </div> </a> <ul id="toc-Permanent_magnet_degausser-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> 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class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Degaussing</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. 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title="Entmagnetisierung – German" lang="de" hreflang="de" data-title="Entmagnetisierung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Desmagnetizaci%C3%B3n" title="Desmagnetización – Spanish" lang="es" hreflang="es" data-title="Desmagnetización" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%D8%BA%D9%86%D8%A7%D8%B7%DB%8C%D8%B3%E2%80%8C%DA%A9%D8%A7%D9%87%DB%8C" title="مغناطیس‌کاهی – Persian" lang="fa" hreflang="fa" data-title="مغناطیس‌کاهی" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/D%C3%A9magn%C3%A9tisation" title="Démagnétisation – French" lang="fr" hreflang="fr" data-title="Démagnétisation" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/D%C3%ADghabhs%C3%A1il" title="Díghabhsáil – Irish" lang="ga" hreflang="ga" data-title="Díghabhsáil" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%94%94%EA%B0%80%EC%9A%B0%EC%8B%B1" title="디가우싱 – Korean" lang="ko" hreflang="ko" data-title="디가우싱" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%B5%E0%A4%BF%E0%A4%9A%E0%A5%81%E0%A4%AE%E0%A5%8D%E0%A4%AC%E0%A4%95%E0%A4%A8" title="विचुम्बकन – Hindi" lang="hi" hreflang="hi" data-title="विचुम्बकन" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Demagnetizacija" title="Demagnetizacija – Croatian" lang="hr" hreflang="hr" data-title="Demagnetizacija" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Demagnetisasi" title="Demagnetisasi – Indonesian" lang="id" hreflang="id" data-title="Demagnetisasi" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Demagnetizzazione" title="Demagnetizzazione – Italian" lang="it" hreflang="it" data-title="Demagnetizzazione" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9C%D0%B0%D0%B3%D0%BD%D0%B8%D1%82%D1%81%D1%96%D0%B7%D0%B4%D0%B5%D0%BD%D1%83" title="Магнитсіздену – Kazakh" lang="kk" hreflang="kk" data-title="Магнитсіздену" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E6%B6%88%E7%A3%81" title="消磁 – Japanese" lang="ja" hreflang="ja" data-title="消磁" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Avmagnetisering" title="Avmagnetisering – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Avmagnetisering" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Avmagnetisering" title="Avmagnetisering – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Avmagnetisering" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Rozmagnesowanie" title="Rozmagnesowanie – Polish" lang="pl" hreflang="pl" data-title="Rozmagnesowanie" 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mw-list-item"><a href="https://fi.wikipedia.org/wiki/Demagnetointi" title="Demagnetointi – Finnish" lang="fi" hreflang="fi" data-title="Demagnetointi" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Degauss" title="Degauss – Turkish" lang="tr" hreflang="tr" data-title="Degauss" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%A0%D0%BE%D0%B7%D0%BC%D0%B0%D0%B3%D0%BD%D1%96%D1%87%D0%B5%D0%BD%D0%BD%D1%8F" title="Розмагнічення – Ukrainian" lang="uk" hreflang="uk" data-title="Розмагнічення" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li 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<div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Process of decreasing or eliminating a remnant magnetic field</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Degassing" title="Degassing">Degassing</a>.</div> <p> <b>Degaussing</b>, or <b>deperming</b>, is the process of decreasing or eliminating a remnant <a href="/wiki/Magnetic_field" title="Magnetic field">magnetic field</a>. It is named after the <a href="/wiki/Gauss_(unit)" title="Gauss (unit)">gauss</a>, a unit of <a href="/wiki/Magnetism" title="Magnetism">magnetism</a>, which in turn was named after <a href="/wiki/Carl_Friedrich_Gauss" title="Carl Friedrich Gauss">Carl Friedrich Gauss</a>. Due to <a href="/wiki/Magnetic_hysteresis" title="Magnetic hysteresis">magnetic hysteresis</a>, it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small "known" field referred to as bias. Degaussing was originally applied to reduce ships' magnetic signatures during <a href="/wiki/World_War_II" title="World War II">World War II</a>. Degaussing is also used to reduce magnetic fields in tape recorders and <a href="/wiki/Cathode-ray_tube" title="Cathode-ray tube">cathode-ray tube</a> displays, and to destroy data held on <a href="/wiki/Magnetic_storage" title="Magnetic storage">magnetic storage</a>. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Ships'_hulls"><span id="Ships.27_hulls"></span>Ships' hulls</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=1" title="Edit section: Ships' hulls"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed_section plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Degaussing" title="Special:EditPage/Degaussing">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a> in this section. Unsourced material may be challenged and removed.</span> <span class="date-container"><i>(<span class="date">December 2011</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:USS_Jimmy_Carter_being_depermed.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/USS_Jimmy_Carter_being_depermed.jpg/250px-USS_Jimmy_Carter_being_depermed.jpg" decoding="async" width="220" height="338" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/11/USS_Jimmy_Carter_being_depermed.jpg/330px-USS_Jimmy_Carter_being_depermed.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/11/USS_Jimmy_Carter_being_depermed.jpg/500px-USS_Jimmy_Carter_being_depermed.jpg 2x" data-file-width="1960" data-file-height="3008" /></a><figcaption><a href="/wiki/USS_Jimmy_Carter" title="USS Jimmy Carter">USS <i>Jimmy Carter</i></a> in the magnetic silencing facility at <a href="/wiki/Naval_Base_Kitsap" title="Naval Base Kitsap">Naval Base Kitsap</a> for her first deperming treatment</figcaption></figure> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:RMS_Queen_Mary_20Jun1945_NewYork.jpeg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2a/RMS_Queen_Mary_20Jun1945_NewYork.jpeg/220px-RMS_Queen_Mary_20Jun1945_NewYork.jpeg" decoding="async" width="220" height="164" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2a/RMS_Queen_Mary_20Jun1945_NewYork.jpeg/330px-RMS_Queen_Mary_20Jun1945_NewYork.jpeg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2a/RMS_Queen_Mary_20Jun1945_NewYork.jpeg/440px-RMS_Queen_Mary_20Jun1945_NewYork.jpeg 2x" data-file-width="2925" data-file-height="2177" /></a><figcaption><a href="/wiki/RMS_Queen_Mary" title="RMS Queen Mary">RMS <i>Queen Mary</i></a> arriving in New York Harbor, 20 June 1945, with thousands of U.S. soldiers – note the prominent degaussing coil running around the hull</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:MES_U10.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/MES_U10.jpg/220px-MES_U10.jpg" decoding="async" width="220" height="199" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/dc/MES_U10.jpg/330px-MES_U10.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/dc/MES_U10.jpg/440px-MES_U10.jpg 2x" data-file-width="1685" data-file-height="1525" /></a><figcaption>Control panel of the <i>MES</i>-device (<i>"Magnetischer Eigenschutz"</i> German: <a href="/wiki/Magnetic_self-protection" title="Magnetic self-protection">magnetic self-protection</a>) in a German submarine</figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Ivan_Gren_landing_ship_(1).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/09/Ivan_Gren_landing_ship_%281%29.jpg/220px-Ivan_Gren_landing_ship_%281%29.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/09/Ivan_Gren_landing_ship_%281%29.jpg/330px-Ivan_Gren_landing_ship_%281%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/09/Ivan_Gren_landing_ship_%281%29.jpg/440px-Ivan_Gren_landing_ship_%281%29.jpg 2x" data-file-width="4000" data-file-height="3000" /></a><figcaption>Close-wrap deperming of the <a href="/wiki/Ivan_Gren-class_landing_ship" title="Ivan Gren-class landing ship"><i>Ivan Gren</i>-class</a> <a href="/wiki/Landing_ship" class="mw-redirect" title="Landing ship">landing ship</a> <a href="/wiki/Russian_landing_ship_Ivan_Gren" title="Russian landing ship Ivan Gren"><i>Ivan Gren</i></a>, 2016. The cables are floated into position before wrapping around the vessel.</figcaption></figure> <p>The term was first used by then-Commander <a href="/wiki/Charles_F._Goodeve" title="Charles F. Goodeve">Charles F. Goodeve</a>, <a href="/wiki/Royal_Canadian_Naval_Volunteer_Reserve" title="Royal Canadian Naval Volunteer Reserve">Royal Canadian Naval Volunteer Reserve</a>, during World War II while trying to counter the German magnetic <a href="/wiki/Naval_mine" title="Naval mine">naval mines</a> that were wreaking havoc on the <a href="/wiki/British_fleet" class="mw-redirect" title="British fleet">British fleet</a>. </p><p>The mines detected the increase in the magnetic field when the steel in a ship concentrated the <a href="/wiki/Earth%27s_magnetic_field" title="Earth's magnetic field">Earth's magnetic field</a> over it. Admiralty scientists, including Goodeve, developed a number of systems to induce a small "N-pole up" field into the ship to offset this effect, meaning that the net field was the same as the background. Since the Germans used the gauss as the unit of the strength of the magnetic field in their mines' triggers (not yet a standard measure), Goodeve referred to the various processes to counter the mines as <i>degaussing</i>. The term became a common word. </p><p>The original method of degaussing was to install electromagnetic coils into the ships, known as <i>coiling</i>. In addition to being able to bias the ship continually, coiling also allowed the bias field to be reversed in the southern hemisphere, where the mines were set to detect "N-pole down" fields. British ships, notably <a href="/wiki/Cruiser" title="Cruiser">cruisers</a> and <a href="/wiki/Battleship" title="Battleship">battleships</a>, were well protected by about 1943. </p><p>Installing such special equipment was, however, far too expensive and difficult to service all ships that would need it, so the navy developed an alternative called <i>wiping</i>, which Goodeve also devised. In this procedure, a large electrical cable with a pulse of about 2000 <a href="/wiki/Ampere" title="Ampere">amperes</a> flowing through it was dragged upwards on the side of the ship, starting at the waterline. For submarines, the current came from the vessels' own propulsion batteries. This induced the proper field into the ship in the form of a slight bias. It was originally thought that the pounding of the sea and the ship's engines would slowly randomize this field, but in testing, this was found not to be a real problem.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> A more serious problem was later realized: as a ship travels through Earth's magnetic field, it will slowly pick up that field, counteracting the effects of the degaussing. From then on captains were instructed to change direction as often as possible to avoid this problem. Nevertheless, the bias did wear off eventually, and ships had to be degaussed on a schedule. </p><p>Smaller ships continued to use wiping through the war. To aid the <a href="/wiki/Dunkirk_evacuation" title="Dunkirk evacuation">Dunkirk evacuation</a>, the British <i>wiped</i> 400 ships in four days.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>During World War II, the <a href="/wiki/United_States_Navy" title="United States Navy">United States Navy</a> commissioned a <a href="/wiki/List_of_mine_warfare_vessels_of_the_United_States_Navy#Degaussing_Ships_(ADG)" title="List of mine warfare vessels of the United States Navy">specialized class of degaussing ships</a> that were capable of performing this function. One of them, <a href="/wiki/USS_Deperm_(ADG-10)" class="mw-redirect" title="USS Deperm (ADG-10)">USS <i>Deperm</i> (ADG-10)</a>, was named after the procedure. </p><p>After the war, the capabilities of the <a href="/wiki/Magnetic_proximity_fuze" title="Magnetic proximity fuze">magnetic fuzes</a> were greatly improved, by detecting not the field itself, but changes in it. This meant a degaussed ship with a magnetic <i>hot spot</i> would still set off the mine. Additionally, the precise orientation of the field was also measured, something a simple bias field could not remove, at least not for all points on the ship. A series of ever-increasingly complex coils were introduced to offset these fuze improvements, with modern systems including no fewer than three separate sets of coils to cancel the field in all axes. </p> <div class="mw-heading mw-heading3"><h3 id="Degaussing_range">Degaussing range</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=2" title="Edit section: Degaussing range"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The effectiveness of ships' degaussing was monitored by shore-based <i>degaussing ranges</i> (or <i>degaussing stations, magnetic ranges</i>) installed beside shipping channels outside ports. The vessel under test passed at a steady speed over loops on the seabed that were monitored from buildings on the shore. The installation was used both to establish the magnetic characteristics of a hull to establish the correct value of degaussing equipment to be installed, or as a "spot check" on vessels to confirm that degaussing equipment was performing correctly. Some stations had active coils that provided magnetic treatment, offering to un-equipped ships some limited protection against future encounters with magnetic mines.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="High-temperature_superconductivity">High-temperature superconductivity</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=3" title="Edit section: High-temperature superconductivity"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The US Navy tested, in April 2009, a prototype of its <a href="/wiki/High-temperature_superconductivity" title="High-temperature superconductivity">High-Temperature Superconducting</a> Degaussing Coil System, referred to as "HTS Degaussing". The system works by encircling the vessel with superconducting ceramic cables whose purpose is to neutralize the ship's magnetic signature, as in the legacy copper systems. The main advantage of the HTS Degaussing Coil system is greatly reduced weight (sometimes by as much as 80%) and increased efficiency.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> </p><p>A ferrous-metal-hulled ship or submarine, by its very nature, develops a magnetic signature as it travels, due to a magneto-mechanical interaction with Earth's magnetic field. It also picks up the magnetic orientation of the Earth's magnetic field where it is built. This signature can be exploited by magnetic mines or facilitate the detection of a submarine by ships or aircraft with <a href="/wiki/Magnetic_anomaly_detector" title="Magnetic anomaly detector">magnetic anomaly detection (MAD)</a> equipment. <a href="/wiki/Navy" title="Navy">Navies</a> use the deperming procedure, in conjunction with degaussing, as a countermeasure against this. </p><p>Specialized deperming facilities, such as the <a href="/wiki/United_States_Navy" title="United States Navy">United States Navy</a>'s <a href="/wiki/Lambert%27s_Point_Deperming_Station" title="Lambert's Point Deperming Station">Lambert's Point Deperming Station</a> at <a href="/wiki/Naval_Station_Norfolk" title="Naval Station Norfolk">Naval Station Norfolk</a>, or Pacific Fleet Submarine Drive-In Magnetic Silencing Facility (MSF) at <a href="/wiki/Joint_Base_Pearl_Harbor%E2%80%93Hickam" title="Joint Base Pearl Harbor–Hickam">Joint Base Pearl Harbor–Hickam</a>, are used to perform the procedure. During a close-wrap magnetic treatment, heavy-gauge <a href="/wiki/Copper" title="Copper">copper</a> cables encircle the hull and superstructure of the vessel, and high electrical currents (up to 4000 <a href="/wiki/Ampere" title="Ampere">amperes</a>) are pulsed through the cables.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> This has the effect of "resetting" the ship's magnetic signature to the ambient level after flashing its hull with electricity. It is also possible to assign a specific signature that is best suited to the particular area of the world in which the ship will operate. In drive-in magnetic silencing facilities, all cables are either hung above, below and on the sides, or concealed within the structural elements of facilities. Deperming is "permanent". It is only done once unless major repairs or structural modifications are done to the ship. </p> <div class="mw-heading mw-heading3"><h3 id="Early_experiments">Early experiments</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=4" title="Edit section: Early experiments"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>With the introduction of <a href="/wiki/Iron" title="Iron">iron</a> ships, the adverse effect of the metal hull on steering <a href="/wiki/Compass" title="Compass">compasses</a> was noted. It was also observed that <a href="/wiki/Lightning" title="Lightning">lightning</a> strikes had a significant effect on compass deviation, identified in some extreme cases as being caused by the reversal of the ship's magnetic signature. In 1866, <a href="/w/index.php?title=Evan_Hopkins&action=edit&redlink=1" class="new" title="Evan Hopkins (page does not exist)">Evan Hopkins</a> of London registered a patent for a process "to depolarise iron vessels and leave them thenceforth free from any compass-disturbing influence whatever". The technique was described as follows: "For this purpose he employed a number of <a href="/wiki/Grove_cell" title="Grove cell">Grove's batteries</a> and electromagnets. The latter were to be passed along the plates till the desired end had been obtained... the process must not be overdone for fear of re-polarising in the opposite direction." The invention was, however, reported to be "incapable of being carried to a successful issue", and "quickly died a natural death".<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div style="clear:both;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="Color_cathode-ray_tubes">Color cathode-ray tubes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=5" title="Edit section: Color cathode-ray tubes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1251242444" /><table class="box-Unreferenced_section plainlinks metadata ambox ambox-content ambox-Unreferenced" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>does not <a href="/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources">cite</a> any <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">sources</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Degaussing" title="Special:EditPage/Degaussing">improve this section</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a>. Unsourced material may be challenged and <a href="/wiki/Wikipedia:Verifiability#Burden_of_evidence" title="Wikipedia:Verifiability">removed</a>.</span> <span class="date-container"><i>(<span class="date">November 2014</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>Color <a href="/wiki/CRT_display" class="mw-redirect" title="CRT display">CRT displays</a>, the technology underlying many television and <a href="/wiki/Computer_monitor" title="Computer monitor">computer monitors</a> before the early 2010s, require degaussing. Many CRT displays use a <a href="/wiki/Shadow_mask" title="Shadow mask">shadow mask</a> (a perforated metal screen) near the front of the tube to ensure that each electron beam hits the corresponding <a href="/wiki/Phosphor#Color_television_CRTs" title="Phosphor">phosphors</a> of the correct color. If this plate becomes magnetized (e.g. if someone sweeps a magnet on the screen or places loudspeakers nearby), it imparts an undesired deflection to the electron beams and the displayed image becomes distorted and discolored. </p><p>To minimize this, CRTs have a copper or aluminum coil wrapped around the front of the display, known as the degaussing coil. Monitors without an internal coil can be degaussed using an external handheld version. Internal degaussing coils in CRTs are generally much weaker than external degaussing coils, since a better degaussing coil takes up more space. A degauss circuit induces an <a href="/wiki/Oscillating" class="mw-redirect" title="Oscillating">oscillating</a> <a href="/wiki/Magnetic_field" title="Magnetic field">magnetic field</a> with a decreasing <a href="/wiki/Amplitude" title="Amplitude">amplitude</a> which leaves the shadow mask with a reduced residual magnetization. </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Degauss-in-progress_at_Dell-Trinitron-monitor.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Degauss-in-progress_at_Dell-Trinitron-monitor.jpg/250px-Degauss-in-progress_at_Dell-Trinitron-monitor.jpg" decoding="async" width="220" height="176" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Degauss-in-progress_at_Dell-Trinitron-monitor.jpg/330px-Degauss-in-progress_at_Dell-Trinitron-monitor.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Degauss-in-progress_at_Dell-Trinitron-monitor.jpg/440px-Degauss-in-progress_at_Dell-Trinitron-monitor.jpg 2x" data-file-width="480" data-file-height="384" /></a><figcaption>A degaussing in progress</figcaption></figure> <p>Many televisions and monitors automatically degauss their picture tube when switched on, before an image is displayed. The high current surge that takes place during this automatic degauss is the cause of an audible "thunk", a loud hum or some clicking noises, which can be heard (and felt) when televisions and CRT computer monitors are switched on, due to the capacitors discharging and injecting current into the coil. Visually, this causes the image to shake dramatically for a short period of time. A degauss option is also usually available for manual selection in the operations menu in such appliances. </p><p>In most commercial equipment the AC current surge to the degaussing coil is regulated by a simple <a href="/wiki/Positive_temperature_coefficient" class="mw-redirect" title="Positive temperature coefficient">positive temperature coefficient</a> (PTC) <a href="/wiki/Thermistor" title="Thermistor">thermistor</a> device, which initially has a low resistance, allowing a high current, but quickly changes to a high resistance, allowing minimal current, due to self-heating of the thermistor. Such devices are designed for a one-off transition from cold to hot at power up; "experimenting" with the degauss effect by repeatedly switching the device on and off may cause this component to fail. The effect will also be weaker, since the PTC will not have had time to cool off. </p> <div class="mw-heading mw-heading2"><h2 id="Magnetic_data_storage_media">Magnetic data storage media</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=6" title="Edit section: Magnetic data storage media"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Data is stored in the <a href="/wiki/Magnetic_media" class="mw-redirect" title="Magnetic media">magnetic media</a>, such as <a href="/wiki/Hard_drive" class="mw-redirect" title="Hard drive">hard drives</a>, <a href="/wiki/Floppy_disk" title="Floppy disk">floppy disks</a>, and <a href="/wiki/Magnetic_tape" title="Magnetic tape">magnetic tape</a>, by making very small areas called <a href="/wiki/Magnetic_domain" title="Magnetic domain">magnetic domains</a> change their magnetic alignment to be in the direction of an applied magnetic field. This phenomenon occurs in much the same way a compass needle points in the direction of the Earth's magnetic field. Degaussing, commonly called erasure, leaves the domains in random patterns with no preference to orientation, thereby rendering previous data unrecoverable. There are some domains whose magnetic alignment is not randomized after degaussing. The information these domains represent is commonly called magnetic <a href="/wiki/Remanence" title="Remanence">remanence</a> or <a href="/wiki/Remanent_magnetization" class="mw-redirect" title="Remanent magnetization">remanent magnetization</a>. Proper degaussing will ensure there is insufficient magnetic remanence to reconstruct the data.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>Erasure via degaussing may be accomplished in two ways: in <a href="/wiki/Alternating_current" title="Alternating current">AC</a> erasure, the medium is degaussed by applying an alternating field that is reduced in amplitude over time from an initial high value (i.e., AC powered); in <a href="/wiki/Direct_current" title="Direct current">DC</a> erasure, the medium is saturated by applying a unidirectional field (i.e., DC powered or by employing a <a href="/wiki/Permanent_magnet#Types_of_permanent_magnets" class="mw-redirect" title="Permanent magnet">permanent magnet</a>). A <i>degausser</i> is a device that can generate a magnetic field for degaussing magnetic storage media.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> The magnetic field needed for degaussing magnetic data storage media is a powerful one that normal magnets cannot easily achieve and maintain.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-vs_10-0" class="reference"><a href="#cite_note-vs-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Irreversible_damage_to_some_media_types">Irreversible damage to some media types</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=7" title="Edit section: Irreversible damage to some media types"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Many forms of generic magnetic storage media can be reused after degaussing, including <a href="/wiki/Reel-to-reel_audio_tape_recording" title="Reel-to-reel audio tape recording">reel-to-reel audio tape</a>, <a href="/wiki/VHS" title="VHS">VHS</a> videocassettes, and <a href="/wiki/Floppy_disk" title="Floppy disk">floppy disks</a>. These older media types are simply a raw medium which are overwritten with fresh new patterns, created by fixed-alignment read/write heads. </p><p>For certain forms of computer data storage, however, such as modern <a href="/wiki/Hard_disk_drive" title="Hard disk drive">hard disk drives</a> and some <a href="/wiki/Tape_drive" title="Tape drive">tape drives</a>, degaussing renders the magnetic media completely unusable and damages the storage system. This is due to the devices having an infinitely variable read/write head positioning mechanism which relies on special servo control data (e.g. <a href="/wiki/Gray_code#Position_encoders" title="Gray code">Gray Code</a><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>) that is meant to be permanently recorded onto the magnetic media. This servo data is written onto the media a single time at the factory using special-purpose servo writing hardware. </p><p>The servo patterns are normally never overwritten by the device for any reason and are used to precisely position the read/write heads over data tracks on the media, to compensate for sudden jarring device movements, thermal expansion, or changes in orientation. Degaussing indiscriminately removes not only the stored data but also the servo control data, and without the servo data the device is no longer able to determine where data is to be read or written on the magnetic medium. The servo data must be rewritten to become usable again; with modern hard drives, this is generally not possible without manufacturer-specific and often model-specific service equipment. </p> <div class="mw-heading mw-heading2"><h2 id="Tape_recorders">Tape recorders</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=8" title="Edit section: Tape recorders"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In tape recorders such as <a href="/wiki/Reel-to-reel_audio_tape_recording" title="Reel-to-reel audio tape recording">reel-to-reel</a> and <a href="/wiki/Cassette_tape" class="mw-redirect" title="Cassette tape">compact cassette</a> audio tape recorders, remnant magnetic fields will over time gather on metal parts such as guide posts tape heads. These are points that come into contact with the magnetic tape. The remnant fields can cause an increase in audible background noise during playback. Cheap, handheld consumer degaussers can significantly reduce this effect.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Types_of_degaussers">Types of degaussers</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=9" title="Edit section: Types of degaussers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Degaussers range in size from small ones used in offices for erasing magnetic data storage devices to industrial-size degaussers for use on piping, ships, submarines, and other large-sized items, equipment to vehicles. Rating and categorizing degaussers depends on the strength of the magnetic field the degausser generates, the method of generating a magnetic field in the degausser, the type of operations the degausser is suitable for, the working rate of the degausser based on whether it is a high volume degausser or a low volume degausser, and mobility of the degausser among others.<sup id="cite_ref-dsi_13-0" class="reference"><a href="#cite_note-dsi-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> From these criteria of rating and categorization, there are thus electromagnetic degaussers, permanent magnet degaussers as the main types of degaussers.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Electromagnetic_degaussers">Electromagnetic degaussers</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=10" title="Edit section: Electromagnetic degaussers"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An electromagnetic degausser passes an electrical charge through a degaussing coil to generate a magnetic field.<sup id="cite_ref-dsi_13-1" class="reference"><a href="#cite_note-dsi-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> Sub-types of electromagnetic degaussers are several such as Rotating Coil Degaussers and Pulse Demagnetization Technology degaussers since the technologies used in the degaussers are often developed and patented by respective manufacturing companies such as Verity Systems and Maurer Magnetic among others, so that the degausser is suitable for its intended use.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Electromagnetic degaussers generate strong magnetic fields, and have a high rate of work. </p> <div class="mw-heading mw-heading4"><h4 id="Rotating_coil_degausser">Rotating coil degausser</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=11" title="Edit section: Rotating coil degausser"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Performance of a degaussing machine is the major determinant of the effectiveness of degaussing magnetic data storage media. Effectiveness does not improve when the media passes through the same degaussing magnetic field more than once. Rotating the media by 90 degrees improves effectiveness of degaussing the media.<sup id="cite_ref-vs_10-1" class="reference"><a href="#cite_note-vs-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> One magnetic media degaussers’ manufacturer, Verity Systems, has used this principle in a rotating coil technique they developed. Their rotating coil degausser passes the magnetic data storage media being erased through a magnetic field generated using two coils in the degaussing machine with the media on a variable-speed conveyor belt. The two coils generating a magnetic field are rotating; with one coil positioned above the media and the other coil positioned below the media.<sup id="cite_ref-vs_10-2" class="reference"><a href="#cite_note-vs-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading4"><h4 id="Pulse_degaussing">Pulse degaussing</h4><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=12" title="Edit section: Pulse degaussing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Pulse degaussing technology involves the cyclic application of electric current for a fraction of a second to the coil being used to generate a magnetic field in the degausser.<sup id="cite_ref-mmpd_17-0" class="reference"><a href="#cite_note-mmpd-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> The process starts with the maximum voltage applied and held for only a fraction of a second to avoid overheating the coil, and then the voltages applied in subsequent seconds are reduced in sequence at varying differences until no current is applied to the coil. Pulse degaussing saves on energy costs, produces high magnetic field strength, is suitable for degaussing large assemblies, and is reliable due to zero-error degaussing achievement.<sup id="cite_ref-mmpd_17-1" class="reference"><a href="#cite_note-mmpd-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Permanent_magnet_degausser">Permanent magnet degausser</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=13" title="Edit section: Permanent magnet degausser"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Permanent magnet degaussers use magnets made using rare earth materials. They do not require electricity for their operation. Permanent magnet degaussers require adequate shielding of the magnetic field they constantly have to prevent unintended degaussing. The need for shielding usually results in permanent magnet degaussers being bulky. When small-sized, permanent magnet degaussers are suited for use as mobile degaussers.<sup id="cite_ref-dsi_13-2" class="reference"><a href="#cite_note-dsi-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=14" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/40px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/60px-Commons-logo.svg.png 1.5x" data-file-width="1024" data-file-height="1376" /></a></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Deperming" class="extiw" title="commons:Category:Deperming">Deperming</a></span>.</div></div> </div> <ul><li><a href="/wiki/Data_remanence" title="Data remanence">Data remanence</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=15" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFRowlandBoyd1953" class="citation book cs1">Rowland, Burford; Boyd, Wiliam B. (1953). <i>U. S. Navy Bureau of Ordnance in World War II</i>. Washington, D.C.: Bureau of Ordnance, Dept. of the Navy. p. 84. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/7833847">7833847</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=U.+S.+Navy+Bureau+of+Ordnance+in+World+War+II&rft.place=Washington%2C+D.C.&rft.pages=84&rft.pub=Bureau+of+Ordnance%2C+Dept.+of+the+Navy&rft.date=1953&rft_id=info%3Aoclcnum%2F7833847&rft.aulast=Rowland&rft.aufirst=Burford&rft.au=Boyd%2C+Wiliam+B.&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADegaussing" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text">PBS Nova "Great Escape at Dunkirk" <a rel="nofollow" class="external free" href="https://www.pbs.org/video/great-escape-at-dunkirk-qb5qcr/">https://www.pbs.org/video/great-escape-at-dunkirk-qb5qcr/</a></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation book cs1"><i>Shipboard Electrical Systems</i> (1966 ed.). 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Retrieved <span class="nowrap">3 October</span> 2021</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Maurer+Magnetic&rft.atitle=Demagnetization+%E2%80%94+Basics+and+Know-how&rft_id=http%3A%2F%2Fmaurermagnetic.com%2Fen%2Fdemagnetizing%2Ftechnology%2Fdemagnetisation-technology%2F%23%21%2Fmaurer-magnetic-pulse-demagnetisation&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADegaussing" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Degaussing&action=edit&section=16" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://www.buchanan1.net/purple_spot.html">Guide to degaussing TVs</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20200729043846/http://www.buchanan1.net/purple_spot.html">Archived</a> 2020-07-29 at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFVerity_Systems" class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.veritysystems.com/degaussing-an-introduction/">"Degaussing: An Introduction"</a>. Verity Systems. <q>What is a Degausser? It is a machine used to eliminate data stored on computer and laptop hard drives, floppy disks and magnetic tape, by randomly changing the alignment of magnetic domains on the medium.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Degaussing%3A+An+Introduction&rft.pub=Verity+Systems&rft_id=https%3A%2F%2Fwww.veritysystems.com%2Fdegaussing-an-introduction%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADegaussing" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160304103802/http://www.cerberussystems.com/INFOSEC/stds/ncsctg25.htm">"A Guide to Understanding Data Remanence in Automated Information Systems"</a>. <i>www.cerberussystems.com</i>. Archived from <a rel="nofollow" class="external text" href="http://www.cerberussystems.com/INFOSEC/stds/ncsctg25.htm">the original</a> on 4 March 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=www.cerberussystems.com&rft.atitle=A+Guide+to+Understanding+Data+Remanence+in+Automated+Information+Systems&rft_id=http%3A%2F%2Fwww.cerberussystems.com%2FINFOSEC%2Fstds%2Fncsctg25.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ADegaussing" class="Z3988"></span></li> <li><a rel="nofollow" class="external free" href="https://degaussing-101.com/what-is-degaussing/">https://degaussing-101.com/what-is-degaussing/</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Degaussing&oldid=1282560785">https://en.wikipedia.org/w/index.php?title=Degaussing&oldid=1282560785</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Computer_storage_media" title="Category:Computer storage media">Computer storage media</a></li><li><a href="/wiki/Category:Magnetic_data_storage" title="Category:Magnetic data storage">Magnetic data storage</a></li><li><a href="/wiki/Category:Magnetic_hysteresis" title="Category:Magnetic hysteresis">Magnetic hysteresis</a></li><li><a href="/wiki/Category:British_inventions" title="Category:British inventions">British inventions</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li><li><a href="/wiki/Category:Use_dmy_dates_from_October_2022" title="Category:Use dmy dates from October 2022">Use dmy dates from October 2022</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_December_2011" title="Category:Articles needing additional references from December 2011">Articles needing additional references from December 2011</a></li><li><a href="/wiki/Category:All_articles_needing_additional_references" title="Category:All articles needing additional references">All articles needing additional references</a></li><li><a href="/wiki/Category:Articles_needing_additional_references_from_November_2014" title="Category:Articles needing additional references from November 2014">Articles needing additional references from November 2014</a></li><li><a href="/wiki/Category:Commons_category_link_is_locally_defined" title="Category:Commons category link is locally defined">Commons category link is locally defined</a></li><li><a href="/wiki/Category:Webarchive_template_wayback_links" title="Category:Webarchive template wayback links">Webarchive template wayback links</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 27 March 2025, at 04:49<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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