*體積電阻率表面電阻率測(cè)試儀（三電極法）
型號(hào)：BEST-121
一、體積電阻率表面電阻率測(cè)試儀特點(diǎn)
本儀器既可測(cè)量超高電阻,又可測(cè)極微弱電流。采用了大規(guī)模集成電路以及的技 術(shù)，使儀器體積小、重量輕、準(zhǔn)確度高。以數(shù)字液晶顯示電阻并同時(shí) 直接顯示流過(guò)被測(cè)電阻的電流。電阻量限從1×104Ω～1×1018Ω， 電流測(cè)量范圍 為2×10-4A～1×10-16A。機(jī)內(nèi)測(cè)試電壓為DC10V、50V、100V、250V、500V、1000V。本儀器具有精度高、顯示迅速、性好穩(wěn)定、讀數(shù)方便, 適用于防靜電產(chǎn)品如防靜電鞋、防靜電塑料橡膠制品、計(jì)算機(jī)房防靜電活動(dòng)地板等電阻值的檢驗(yàn)以及絕緣材料和電子電器產(chǎn)品的絕緣電阻測(cè)量。本儀器除能測(cè)電阻外，還能直接測(cè)量電流如電子器件暗電流等。
二、體積電阻率表面電阻率測(cè)試儀測(cè)量指標(biāo)
1 電阻測(cè)量范圍 1×104Ω～1×1018Ω；
2 電流測(cè)量范圍 2×10-4Ａ～1×10-16Ａ；
3 體積小、重量輕、準(zhǔn)確度高；
4 *的被測(cè)電阻、和流過(guò)電阻的電流雙顯示，使操作測(cè)量更加方便；
5 性能穩(wěn)定、讀數(shù)方便；
6 既能測(cè)電阻又能測(cè)電流；
7 測(cè)試電壓有六種選擇之多DC10V、50V、100V、250V、500V、1000V；
8 使用操作簡(jiǎn)便，在任何電阻量程和測(cè)試電壓下均直接讀顯示數(shù)字結(jié)果，
免去要乘以一個(gè)系數(shù)的麻煩，使測(cè)量超高電阻就如用萬(wàn)用表測(cè)量普通電阻樣簡(jiǎn)便。
三、適用的主要標(biāo)準(zhǔn)：
GB/T 1410-2006 固體絕緣材料 體積電阻率和表面電阻率試驗(yàn)方法
GB 12014 防靜電工作服
GB/T 20991-2007 個(gè)體防護(hù)裝備 鞋的測(cè)試方法
GB 4385-1995 防靜電鞋、導(dǎo)電鞋技術(shù)要求
GB 12158-2006 防止靜電事故通用導(dǎo)則
GB 4655-2003 橡膠工業(yè)靜電安全規(guī)程
GB/T 12703.4-2010 紡織品 靜電性能的評(píng)定 第4部分 電阻率
GB/T 12703.6-2010 紡織品 靜電性能的評(píng)定 第6部分 纖維泄漏電阻
GB 13348-2009 液體石油產(chǎn)品靜電安全規(guī)程
GB/T 15738-2008 導(dǎo)電和抗靜電纖維增強(qiáng)塑料電阻率試驗(yàn)方法
GB/T 18044-2008 地毯 靜電習(xí)性評(píng)價(jià)法 行走試驗(yàn)
GB/T 18864-2002 硫化橡膠 工業(yè)用抗靜電和導(dǎo)電產(chǎn)品 電阻極限范圍
GB/T 22042-2008 服裝 防靜電性能 表面電阻率試驗(yàn)方法
GB/T 22043-2008 服裝 防靜電性能 通過(guò)材料的電阻（垂直電阻）試驗(yàn)方法
GB/T 24249-2009 防靜電潔凈織物
GB 26539-2011 防靜電陶瓷磚 Antistatic ceramic tiles
GB/T 26825-2011 抗靜電防腐膠
GB 50515-2010 導(dǎo)（防）靜電地面設(shè)計(jì)規(guī)范
GB 50611-2010 電子工程防靜電設(shè)計(jì)規(guī)范
GJB 105-1998-Z 電子產(chǎn)品防靜電放電控制手冊(cè)
GJB 3007A-2009 防靜電工作區(qū)技術(shù)要求
GJB 5104-2004 無(wú)線電引信風(fēng)帽用防靜電涂料及風(fēng)帽靜電性能通用要求
四、體積電阻率表面電阻率測(cè)試儀技術(shù)指標(biāo)
1. 電阻測(cè)量范圍： 1×104Ω ～1×1018Ω，分為十個(gè)量程。
2. 電流測(cè)量范圍為2×10-4A ～1×10-16A
3. 全數(shù)字液晶屏顯示。
4. 準(zhǔn)確度: 準(zhǔn)確度優(yōu)于下表:
量程 有效顯示范圍 20～30℃ RH<80%
104 0.01~19.99 1%
105 0.01～19.99 1%
106 0.01～19.99 1%
107 0.01～19.99 1%
108 0.01～19.99 1%
109 0.01～19.99 1%
1010 0.01～19.99 5%+2字
1011 0.01～19.99 5%+2字
1012 0.01～19.99 5%+5字
1013 0.01～19.99 10%+5字
1014 0.01～19.99 10%+5字
1014以上 0.01～19.99 10-15%+5字
（ 超出有效顯示范圍時(shí)誤差有可能增加）
測(cè)試電流準(zhǔn)確度與電阻相同）
測(cè)試電壓準(zhǔn)確度為 10%
5. 使用環(huán)境: 溫度 -10℃～50℃ 相對(duì)濕度<90%。
6. 測(cè)試電壓: DC10V、50V、100V、250V、500V、1000V。±10%
7. 供電形式: AC 220V，50HZ，功耗約10W。
8. 儀器尺寸: 300ｍｍ× 280ｍｍ× 150 mm。
9. 質(zhì)量: 約3.0KG。
五、名詞術(shù)語(yǔ)
1） 絕緣電阻：施加在與試樣相接觸的二電極之間的直流電壓除以通過(guò)兩電極的總電流所得的商。它取決于體積電阻和表面電阻。
2） 體積電阻：在試樣的相對(duì)兩表面上放置的兩電極間所加直流電壓與流過(guò)兩個(gè)電極之間的穩(wěn)態(tài)電流之商；該電流不包括沿材料表面的電流。在兩電極間可能形成的極化忽略不計(jì)。
3） 體積電阻率：絕緣材料里面的直流電場(chǎng)強(qiáng)度與穩(wěn)態(tài)電流密度之商，即單位體積內(nèi)的體積電阻。
4） 表面電阻：在試樣的某一表面上兩電極間所加電壓與經(jīng)過(guò)一定時(shí)間后流過(guò)兩電極間的電流之商；該電流主要為流過(guò)試樣表層的電流，也包括一部分流過(guò)試樣體積的電流成分。在兩電極間可能形成的極化忽略不計(jì)。
表面電阻率：在絕緣材料的表面層的直流電場(chǎng)強(qiáng)度與線電流密度之商，即單位面積內(nèi)的表面電阻。
六、測(cè)量技術(shù)
a.通常，絕緣材料用于電氣系統(tǒng)的各部件相互絕緣和對(duì)地絕緣，固體絕緣材料還起機(jī)械支撐作用。一般希望材料有盡可能高的絕緣電阻，并具有合適的機(jī)械、化學(xué)和耐熱性能。
b.絕緣材料的電阻率一般都很高，也就是傳導(dǎo)電流很小。如果不注意外界因素的干擾和漏電流的影響，測(cè)量結(jié)果就會(huì)發(fā)生很大的誤差。同時(shí)絕緣材料本身的吸濕性和環(huán)境條件的變化對(duì)測(cè)量結(jié)果也有很大影響。
c.影響體積電阻率和表面電阻率測(cè)試的主要因素是溫度和濕度、電場(chǎng)強(qiáng)度、充電時(shí)間及殘余電荷等。體積電阻率可作為選擇絕緣材料的一個(gè)參數(shù)，電阻率隨溫度和濕度的變化而顯著變化。體積電阻率的測(cè)量常常用來(lái)檢查絕緣材料是否均勻，或者用來(lái)檢測(cè)那些能影響材料質(zhì)量而又不能用其他方法檢測(cè)到的導(dǎo)電雜質(zhì)。
d.由于體積電阻總是要被或多或少地包括到表面電阻的測(cè)試中去，因此只能近似地測(cè)量表面電阻，測(cè)得的表面電阻值主要反映被測(cè)試樣表面污染的程度。所以，表面電阻率不是表征材料本身特性的參數(shù)，而是一個(gè)有關(guān)材料表面污染特性的參數(shù)。當(dāng)表面電阻較高時(shí)，它常隨時(shí)間以不規(guī)則的方式變化。測(cè)量表面電阻通常都規(guī)定1min的電化時(shí)間。
（1）溫度和濕度：固體絕緣材料的絕緣電阻率隨溫度和濕度的升高而降低，特別是體積電阻率隨溫度改變而變化非常大。因此，電瓷材料不但要測(cè)定常溫下的體積電阻率，而且還要測(cè)定高溫下的體積電阻率，以評(píng)定其絕緣性能的好壞。由于水的電導(dǎo)大，隨著濕度增大，表面電阻率和有開口孔隙的電瓷材料的體積電阻率急劇下降。因此，測(cè)定時(shí)應(yīng)嚴(yán)格地按照規(guī)定的試樣處理要求和測(cè)試的環(huán)境條件下進(jìn)行。
（2）電場(chǎng)強(qiáng)度：當(dāng)電場(chǎng)強(qiáng)度比較高時(shí)，離子的遷移率隨電場(chǎng)強(qiáng)度增高而增大，而且在接近擊穿時(shí)還會(huì)出現(xiàn)大量的電子遷移，這時(shí)體積電阻率大大地降低。因此在測(cè)定時(shí)，施加的電壓應(yīng)不超過(guò)規(guī)定的值。
（3）殘余電荷：試樣在加工和測(cè)試等過(guò)程中，可能產(chǎn)生靜電，電阻越高越容易產(chǎn)生靜電，影響測(cè)量的準(zhǔn)確性。因此，在測(cè)量時(shí)，試樣要*放電，即可將幾個(gè)電極連在一起進(jìn)行短路。
（4）雜散電勢(shì)的消除：在絕緣電阻測(cè)量電路中，可能存在某些雜散電勢(shì)，如熱電勢(shì)、電解電勢(shì)、接觸電勢(shì)等，其中影響zui大的為電解電勢(shì)。用高阻計(jì)測(cè)量表面潮濕的試樣的體積電阻時(shí)，測(cè)量極與保護(hù)極間可產(chǎn)生20mv的電勢(shì)。試驗(yàn)前應(yīng)檢查有無(wú)雜散電勢(shì)?？筛鶕?jù)試樣加壓前后高阻計(jì)的二次指示是否相同來(lái)判斷有無(wú)雜散電勢(shì)。如相同，證明無(wú)雜散電勢(shì)；否則應(yīng)當(dāng)尋找并排除產(chǎn)生雜散電勢(shì)的根源，才能進(jìn)行測(cè)量。
（5）防止漏電流的影響：對(duì)于高電阻材料，只有采取保護(hù)技術(shù)才能去除漏電流對(duì)測(cè)量的影響。保護(hù)技術(shù)就是在引起測(cè)量誤差的漏電路徑上安置保護(hù)導(dǎo)體，截住可能引起測(cè)量誤差的雜散電流，使之不流經(jīng)測(cè)量回路或儀表。保護(hù)導(dǎo)體連接在一起構(gòu)成保護(hù)端，通常保護(hù)端接地。測(cè)量體積電阻時(shí)，三電極系統(tǒng)的保護(hù)極就是保護(hù)導(dǎo)體。此時(shí)要求保護(hù)電極和測(cè)量電極間的試樣表面電阻高于與它并聯(lián)元件的電阻10～100倍。線路接好后，應(yīng)首先檢查是否存在漏電。此時(shí)斷開與試樣連接的高壓線，加上電壓。如在測(cè)量靈敏度范圍內(nèi)，測(cè)量?jī)x器指示的電阻值為無(wú)限大，則線路無(wú)漏電，可進(jìn)行測(cè)量。
（6）條件處理和測(cè)試條件的規(guī)定:固體絕緣材料的電阻隨溫度、濕度的增加而下降。試樣的預(yù)處理?xiàng)l件取決于被測(cè)材料，這些條件在材料規(guī)范中規(guī)定。*使用GB10580《固體絕緣材料在試驗(yàn)前和試驗(yàn)時(shí)采用的標(biāo)準(zhǔn)條件》中規(guī)定的預(yù)處理方法?？墒褂酶视?mdash;水溶液潮濕箱進(jìn)行濕度預(yù)處理。測(cè)試條件應(yīng)與預(yù)處理?xiàng)l件盡可能地*，有些時(shí)候（如浸水處理）不能保持預(yù)處理?xiàng)l件和測(cè)試條件*時(shí)，則應(yīng)在從預(yù)處理環(huán)境中取出后在盡可能短時(shí)間內(nèi)完成測(cè)試，一般不超過(guò)5分鐘。
（7）電化時(shí)間的規(guī)定:當(dāng)直流電壓加到與試樣接觸的兩電極間時(shí)，通過(guò)試樣的電流會(huì)指數(shù)式地衰減到一個(gè)穩(wěn)定值。電流隨時(shí)間的減小可能是由于電介質(zhì)極化和可動(dòng)離子位移到電極所致。對(duì)于體積電阻率小于1010Ω·m的材料，其穩(wěn)定狀態(tài)通常在1分鐘內(nèi)達(dá)到。因此，要經(jīng)過(guò)這個(gè)電化時(shí)間后測(cè)定電阻。對(duì)于電阻率較高的材料，電流減小的過(guò)程可能會(huì)持續(xù)幾分鐘、幾小時(shí)、幾天，因此需要用較長(zhǎng)的電化時(shí)間。如果需要的話，可用體積電阻率與時(shí)間的關(guān)系來(lái)描述材料的特性。當(dāng)表面電阻較高時(shí)，它常隨時(shí)間以不規(guī)則的方式變化。測(cè)量表面電阻通常都規(guī)定1分鐘的電化時(shí)間
。
七、體積電阻率表面電阻率測(cè)試儀使用注意事項(xiàng)：
高阻測(cè)量一定要嚴(yán)格按使用方法步聚進(jìn)行，否則有可能造成儀器*損壞或電人。
１、 應(yīng)在“Ｒｘ”兩端開路時(shí)調(diào)零 如接在電阻箱或被測(cè)量物體上時(shí)調(diào)零后測(cè)量會(huì)產(chǎn)生很大的誤差。一般一次調(diào)零后在測(cè)試過(guò)程中不需再調(diào)零，但改變測(cè)量電壓后可能要重新調(diào)零。
２、 禁止將“Ｒｘ”兩端短路，以免微電流放大器受大電流沖擊
３、 在測(cè)試過(guò)程中不要隨意改動(dòng)測(cè)量電壓， 隨意改動(dòng)測(cè)量電壓可能因電壓的過(guò)高或電流過(guò)大損壞被測(cè)試器件或測(cè)試儀器，而且有的材料是非線性的，即電壓與電流是不符合歐姆定律，有改變電壓時(shí)由于電流不是線性變化，所以測(cè)量的電阻也會(huì)變化。
４、 測(cè)量時(shí)從低次檔逐漸拔往高次檔 每撥一次稍停留1～2秒以便觀察顯示數(shù)字，當(dāng)有顯示值時(shí)應(yīng)停下，記錄當(dāng)前的數(shù)字即是被測(cè)電阻值。若顯示“1”時(shí)，表示欠量程應(yīng)往高次檔拔。直到有顯示數(shù)字時(shí)為止。當(dāng)有顯示數(shù)字時(shí)不能再往高次檔撥，否則有可能損壞儀器（機(jī)內(nèi)有過(guò)電流保護(hù)電路）。除104 Ω檔之外，當(dāng)顯示低于1.99，表示過(guò)量程應(yīng)換低檔!
５、 大部分絕緣材料，特別是防靜電材料的電阻值在加電壓后會(huì)有一定變化而引起數(shù)字變化 由于本儀器的分辯率很高，因而會(huì)引起顯示值的末尾幾位數(shù)也變化，這不是儀器本身的問(wèn)題，而是被測(cè)量對(duì)象的導(dǎo)電機(jī)理復(fù)雜而使得阻值有些變化。在這種情況下往往取2位有效數(shù)就夠了。
６ 、接通電源后，手指不能觸及高壓線的金屬部分 本儀表有二連根線：高壓線（紅）和微電流測(cè)試線。在使用時(shí)要注意高壓線，開機(jī)后人不能觸及高壓線，以免電人或麻手。
７ 、測(cè)試過(guò)程中不能觸摸微電流測(cè)試端 微電流測(cè)試端zui怕受到大電流或人體感應(yīng)電壓及靜電的沖擊。所以在開機(jī)后和測(cè)試過(guò)程中不能與微電流測(cè)試端接觸，以免損壞儀表。
８、 在測(cè)量高阻時(shí)，應(yīng)采用屏蔽盒將被測(cè)物體屏蔽． 在測(cè)量大于1010 Ω以上時(shí)，為防止外界干擾面而引起讀數(shù)不穩(wěn)。
９、 每次測(cè)量完時(shí)應(yīng)將量程開關(guān)撥回“１０４ ”檔再進(jìn)行下次測(cè)試 在測(cè)量時(shí)應(yīng)逐漸將量程開關(guān)撥到高阻檔，測(cè)量完時(shí)應(yīng)將量程開關(guān)撥回低檔。以確保下次開機(jī)時(shí)量程開關(guān)處在低阻量程檔。
人體一般可以帶上幾千甚至幾萬(wàn)伏靜電！
八、高阻測(cè)量常見(jiàn)問(wèn)題
1 。為什么在測(cè)量同一物體時(shí)用不同的電阻量程有不同的讀 數(shù)？
這是因?yàn)闇y(cè)量電阻時(shí)為防止過(guò)電壓損壞儀器，如果出現(xiàn)過(guò)量程時(shí)儀器內(nèi)保護(hù)電路 開始工作，將測(cè)試電壓降下來(lái)以保護(hù)機(jī)內(nèi)放大器。在不同的電壓下測(cè)量同一物體會(huì) 有不同的結(jié)果。而且當(dāng)測(cè)量電阻時(shí)若讀數(shù)小于199，既只為三位數(shù)且*位數(shù)為1 時(shí)，其準(zhǔn)確度要下降。所以在測(cè)量電阻時(shí)當(dāng)*次讀數(shù)從1 變?yōu)槟骋蛔x數(shù)時(shí)，不應(yīng) 再往更高的量程扭開關(guān)以防對(duì)儀器造成過(guò)大的電流沖擊。在實(shí)際使用時(shí)，即讀數(shù)位 數(shù)多的比讀數(shù)位數(shù)少的準(zhǔn)確度高。
2 ．為什么測(cè)量一些物體的電流時(shí)用不同的量程也會(huì)出現(xiàn)測(cè)出結(jié) 果相差較大？
這是因?yàn)橐话阄矬w輸出的電流不是恒定流，而儀器有一定內(nèi)阻，若在儀器上所選 量程的內(nèi)阻過(guò)大以至于在儀器上的電壓降影響被測(cè)物體的輸出電流時(shí)會(huì)造成測(cè)量誤差。一般電流越小的量程內(nèi)阻越高，所以在測(cè)量電流時(shí)應(yīng)選用電流大的量程。在實(shí) 際使用時(shí)即只要電流表有讀數(shù)時(shí)，讀數(shù)位數(shù)少的小的比讀數(shù)位數(shù)多的準(zhǔn)確度高。
3．為什么測(cè)量時(shí)儀器的讀數(shù)總是不穩(wěn)？
一般的材料其導(dǎo)電性不是嚴(yán)格像標(biāo)準(zhǔn)電阻樣在一定的電壓下有很穩(wěn)定的電流，有 很多材料特別是防靜電材料其導(dǎo)電性不符合歐姆定律，所以在測(cè)量時(shí)其讀數(shù)不穩(wěn)。 這不是儀器的問(wèn)題，而是被測(cè)量物體的性能決定的。有的標(biāo)準(zhǔn)規(guī)定以測(cè)量1分鐘時(shí)間 的讀數(shù)為準(zhǔn)。通常在測(cè)量高電阻或微電流時(shí)測(cè)量準(zhǔn)確度因重復(fù)性不好，對(duì)測(cè)量讀數(shù) 只要求2位或3位。另外在測(cè)量大電阻時(shí)如果屏蔽不好也會(huì)因外界的電磁信號(hào)對(duì)儀器 測(cè)量結(jié)果造成讀數(shù)不穩(wěn)。
4. 這是因?yàn)樵跍y(cè)量時(shí)被測(cè)物體及儀器輸入端都有一定的電容，這個(gè)電容在測(cè)量時(shí)已 被充電到測(cè)量電阻時(shí)的電壓值，如果儀器不撥到104擋后關(guān)電源這個(gè)充電后的電容器 會(huì)對(duì)儀器內(nèi)的放大器放電而造成儀器損壞。當(dāng)被測(cè)量物體電容越大，測(cè)試電壓越高 時(shí)，電容器所儲(chǔ)藏的電能越大，更容易損壞儀器，特別是在電阻的高量程或電流的 低量程時(shí)因儀器非常靈敏，儀器過(guò)載而損壞的可能性更大。所以一定要將量程開關(guān) 再撥到104擋后才能關(guān)電源。
5。 為什么在測(cè)量電阻過(guò)程中不要改變對(duì)被測(cè)物的測(cè)試電 壓？
在測(cè)量電阻過(guò)程中如果改變對(duì)被測(cè)物的測(cè)試電壓，無(wú)論電壓變高或變低時(shí)都將 會(huì)產(chǎn)生大脈沖電流，這個(gè)大的電流很有可能使儀器過(guò)量程甚至更損壞儀器。另一方 面如果電壓突然變化也會(huì)通過(guò)被測(cè)量物體的（分布）電容放電或反向放電對(duì)測(cè)量?jī)x 器造成沖擊而損壞儀器。有的物體的耐壓較低，當(dāng)您改變測(cè)量電壓時(shí)有右能擊穿而 產(chǎn)生大電流損壞儀器。如果要改變測(cè)量電壓，在確保被測(cè)量物體不會(huì)因電壓過(guò)高擊 穿時(shí)，要先將量程開關(guān)撥到104檔后關(guān)閉電源，再?gòu)膬x器后面板調(diào)整到所要求的電 壓。有的材料是非線性的，即電壓與電流是不符合歐姆定律，有改變電壓時(shí)由于電流不是線性變化，所以測(cè)量的電阻也會(huì)變化。
6 。為什么測(cè)量完畢要將量程開關(guān)再撥到 104 檔后關(guān)閉電源？
這是因?yàn)闄C(jī)內(nèi)的電容器充有很高的電壓（zui高電壓達(dá)1200V以上），這些電容器的 所帶的電能保持較長(zhǎng)的時(shí)間，如果關(guān)閉電源開關(guān)，則會(huì)將機(jī)內(nèi)的高壓電容器很快放 電，不會(huì)在測(cè)量的高壓端留有很危險(xiǎn)的電壓造成電擊。如果僅撥電源線而不是關(guān)電 源開頭，雖然斷了電源，但機(jī)內(nèi)高壓電容器還有會(huì)因長(zhǎng)時(shí)間保持很高的電壓，將會(huì) 對(duì)人員或其它物體造成電擊或損壞。在儀器有問(wèn)題時(shí)也不要隨便打開機(jī)箱因機(jī)內(nèi)高壓造成電擊，要將儀器找專業(yè)技術(shù)人員或寄回廠家修理。
九、體積電阻率表面電阻率測(cè)試儀主要應(yīng)用范圍
a 材料高阻測(cè)試測(cè)量如防靜電產(chǎn)品（防靜電鞋、防靜電塑料橡膠制品、計(jì) 算機(jī)房防靜電活動(dòng)地板等）電阻值的檢測(cè)；
b 材料體積電阻（率）和表面電阻（率）測(cè)量；
c 電化學(xué)和材料測(cè)試,以及物理,光學(xué)和材料研究;
d 微弱電流測(cè)量如光電效應(yīng)和器件暗電流測(cè)量。
附加介紹：
電阻率
電阻率是用來(lái)表示各種物質(zhì)電阻特性的物理量。某種材料制成的長(zhǎng)1米、橫截面積是1平方毫米的在常溫下（20℃時(shí)）導(dǎo)線的電阻，叫做這種材料的電阻率。電阻率的單位是歐姆·米（Ω·m或ohmm），常用單位是歐姆·毫米和歐姆·米。
應(yīng)用
電阻率較低的物質(zhì)被稱為導(dǎo)體，常見(jiàn)導(dǎo)體主要為金屬，而自然界中導(dǎo)電性*的是銀，其次為半導(dǎo)體，、硅鍺。當(dāng)存在外電場(chǎng)時(shí)，金屬的自由電子在運(yùn)動(dòng)中不斷和晶格節(jié)點(diǎn)上做熱振子的正離子相碰撞，使電子運(yùn)動(dòng)受到阻礙，因而就具有了一定的電阻。其他不易導(dǎo)電的物質(zhì)如玻璃、橡膠等，電阻率較高，一般稱為絕緣體。介于導(dǎo)體和絕緣體之間的物質(zhì)（如硅） 則稱半導(dǎo)體。電阻率的科學(xué)符號(hào)為 ρ（Rho）。 已知物體的電阻，可由電阻率ρ、長(zhǎng)度 l 與截面面積A 計(jì)算：ρ=RA/I，在該式中， 電阻R 單位為歐姆，長(zhǎng)度 l 單位為米，截面面積 A 單位為平方米，電阻率 ρ單位為
歐姆·米
計(jì)算公式
電阻率的計(jì)算公式為：ρ=RS/L
ρ為電阻率——常用單位Ω·m
S為橫截面積——常用單位㎡
R為電阻值——常用單位Ω
L為導(dǎo)線的長(zhǎng)度——常用單位m
-----------------------------------------
電阻率的另一計(jì)算公式為：ρ=E/J
ρ為電阻率——常用單位Ω·mm2/m[1]
E為電場(chǎng)強(qiáng)度——常用單位N/C
J為電流密度——常用單位A/㎡
（E，J 可以為矢量）
說(shuō)明
1．電阻率ρ不僅和導(dǎo)體的材料有關(guān)，還和導(dǎo)體的溫度有關(guān)。在溫度變化不大的范圍內(nèi)：幾乎所有金屬的電阻率隨溫度作線性變化，即ρ=ρo（1+at）。式中t是攝氏溫度，ρo是O℃時(shí)的電阻率，a是電阻率溫度系數(shù)。
2．由于電阻率隨溫度改變而改變，所以對(duì)于某些電器的電阻，必須說(shuō)明它們所處的物理狀態(tài)。如一個(gè)220 V -100 W電燈燈絲的電阻，通電時(shí)是484歐姆，未通電時(shí)只有40歐姆左右。
3．電阻率和電阻是兩個(gè)不同的概念。電阻率是反映物質(zhì)對(duì)電流阻礙作用的屬性，電阻是反映物體對(duì)電流阻礙作用的屬性。
總結(jié)：
常態(tài)下（由表可知）導(dǎo)電性能的依次是銀、銅、鋁，這三種材料是zui常用的，常被用來(lái)作為導(dǎo)線等，其中銅用的zui為廣，幾乎現(xiàn)在的導(dǎo)線都是銅的（精密儀器，特殊場(chǎng)合除外）鋁線由于化學(xué)性質(zhì)不穩(wěn)定容易氧化已被淘汰。由于鋁密度小，取材廣泛，且價(jià)格比銅便宜，目前被廣泛用于電力系統(tǒng)中傳輸電力的架空輸電線路。為解決鋁材剛性不足缺陷，一般采用鋼芯鋁絞線，即鋁絞線內(nèi)部包有一根鋼線，以提高強(qiáng)度。銀導(dǎo)電性能，但由于成本高很少被采用，只有在高要求場(chǎng)合才被使用，如精密儀器、高頻震蕩器、航天等。順便說(shuō)下金，在某些場(chǎng)合儀器上觸點(diǎn)也有用金的，那是因?yàn)榻鸬幕瘜W(xué)性質(zhì)穩(wěn)定故采用，并不是因?yàn)槠潆娮杪市∷隆?/p>
北京北廣精儀儀器設(shè)備有限公司*產(chǎn)品：
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售后服務(wù)及保修承諾：
多年來(lái)，我公司一直專業(yè)生產(chǎn)研究電氣試驗(yàn)設(shè)備，經(jīng)研究、摸索、總結(jié)出一套完整的產(chǎn)品服務(wù)保障體系，向用戶提供優(yōu)質(zhì)及時(shí)的售前、售中、售后服務(wù)
為創(chuàng)造，提高企業(yè)度，樹立企業(yè)形象，我們本著“一切追求高質(zhì)量，用戶滿意為宗旨”的精神，以“*惠的價(jià)格、zui周到的服務(wù)、zui可靠的產(chǎn)品質(zhì)量”的原則向您鄭重承諾：
一、產(chǎn)品質(zhì)量承諾：
1、我公司保證向需方提供的設(shè)備是原廠生產(chǎn)的，并且出廠資料配件齊全。為保持合同設(shè)備的正常運(yùn)行和維護(hù)，我公司保證提供的技術(shù)資料和圖紙是完整、清楚和正確的。
2、產(chǎn)品的制造和檢測(cè)均有質(zhì)量記錄和檢測(cè)資料。
3、對(duì)產(chǎn)品性能的檢測(cè)，我們誠(chéng)請(qǐng)用戶親臨對(duì)產(chǎn)品進(jìn)行全過(guò)程、全性能檢查，待產(chǎn)品被確認(rèn)合格后再裝箱發(fā)貨。
二、產(chǎn)品價(jià)格承諾：
1、為了保證產(chǎn)品的高可靠性和*性，系統(tǒng)的選材均選用國(guó)內(nèi)或優(yōu)質(zhì)產(chǎn)品。
2、在同等競(jìng)爭(zhēng)條件下，我公司在不以降低產(chǎn)品技術(shù)性能、更改產(chǎn)品部件為代價(jià)的基礎(chǔ)上，真誠(chéng)以*惠的價(jià)格提供給貴方。
三：安裝調(diào)試及驗(yàn)收承諾：
1、協(xié)助設(shè)備的安裝，負(fù)責(zé)設(shè)備的運(yùn)輸、調(diào)試。
2、設(shè)備按訂貨技術(shù)附件進(jìn)行驗(yàn)收。終驗(yàn)收在買方進(jìn)行，對(duì)用戶提供的試樣進(jìn)行試驗(yàn)，并提供測(cè)試報(bào)告。
3、安裝調(diào)試同時(shí)，在儀器操作現(xiàn)場(chǎng)一次性免費(fèi)培訓(xùn)操作人員2-3名，該操作人員應(yīng)是由需方選派的*穩(wěn)定的員工，培訓(xùn)后能夠?qū)υO(shè)備基本原理、軟件使用、操作、維護(hù)事項(xiàng)理解和應(yīng)用，使人員能夠獨(dú)立操作設(shè)備對(duì)樣品進(jìn)行檢測(cè)、分析，同時(shí)能進(jìn)行基本的維護(hù)。
四、保修承諾：
1、設(shè)備保修一年，終身服務(wù)，一年內(nèi)非人為損壞的零部件免費(fèi)更換，保修期內(nèi)接到用戶邀請(qǐng)后， zui遲響應(yīng)時(shí)間為2小時(shí)內(nèi)，在與用戶確認(rèn)故障后，我公司會(huì)在48小時(shí)內(nèi)派工程師到達(dá)現(xiàn)場(chǎng)進(jìn)行
免費(fèi)服務(wù)，盡快查清故障所在位置和故障原因，并向用戶及時(shí)報(bào)告故障的原因和排除辦法 。
2、保修期內(nèi)人為損壞的零部件按采購(gòu)（加工）價(jià)格收費(fèi)更換。
3、保修期外繼續(xù)為用戶提供優(yōu)質(zhì)技術(shù)服務(wù)，在接到用戶維修邀請(qǐng)后3天內(nèi)派工程師到達(dá)用戶現(xiàn)場(chǎng)進(jìn)行維修。并享有優(yōu)惠購(gòu)買零配件的待遇?！?br />4、傳感器過(guò)載及整機(jī)電路超壓損壞不在保修范圍內(nèi)。
Factory direct sales volume resistivity Surface resistivity tester （three electrode method）
Model: BEST-121
First, the volume resistivity Surface resistivity tester Features
The instrument can measure high resistance, can be measured very weak currents. Using the LSI and the latest patented technology, equipment, small size, light weight, high accuracy. Digital LCD display resistance while direct current flowing through the measured resistance.
Resistance limit from 1 × 104Ω ~ 1 × 1018Ω, the current measuring range of 2 × 10-4A ~ 1 × 10-16A. In test voltage is DC10V, 50V, 100V, 250V, 500V, 1000V. This instrument has high precision, showing rapid, good stability, reading
Convenient for static, such as anti-static shoes, anti-static plastics and rubber products, anti-static raised floor computer room and other resistance testing and insulation materials and electrical and electronic products, insulation resistance measurement. In addition to the instrument can measure resistance, but also can directly measure the electrical
Streams such as electronic devices dark current.
Second, the volume resistivity Surface resistivity tester measure
A resistance measurement range of 1 × 104Ω ~ 1 × 1018Ω;
2 current measurement range 2 × 10-4A ~ 1 × 10-16A;
3, small size, light weight, high accuracy;
4 unique measured resistance, and the current flowing through the resistor dual display makes the operation more convenient measurement;
5 stable performance, easy reading;
6 can measure both current sensing resistor;
7 There are six options as much as test voltage DC10V, 50V, 100V, 250V, 500V, 1000V;
8 Use the easy to operate, at any resistance range and test voltages are read directly show numerical results
Eliminates the trouble to be multiplied by a coefficient, high resistance of the measurement as measured with a multimeter ordinary electric
Resistance like simple.
Third, the main criteria for:
GB / T 1410-2006 volume resistivity of insulating materials and surface resistivity test methods
GB 12014 Antistatic overalls
GB / T 20991-2007 Personal protective equipment - Test methods for footwear
GB 4385-1995 anti-static shoes, conductive shoes technical requirements
GB 12158-2006 General Guidelines for preventing electrostatic accidents
GB 4655-2003 Safety regulations for electrostatic rubber industry
GB / T 12703.4-2010 Textiles electrostatic properties - Part 4 resistivity
GB / T 12703.6-2010 Textiles electrostatic properties - Part 6 fiber leakage resistance
GB 13348-2009 safety rules electrostatic liquid petroleum products
GB / T 15738-2008 conductive and antistatic fiber reinforced plastics resistivity test methods
GB / T 18044-2008 carpet electrostatic habits evaluation walking test
GB / T 18864-2002 vulcanized rubber products for industrial use antistatic and conductive resistance limits
GB / T 22042-2008 clothing antistatic properties of the surface resistivity test methods
GB / T 22043-2008 clothing antistatic properties resistance through a material （vertical resistance） test method
GB / T 24249-2009 anti-static clean fabric
GB 26539-2011 Antistatic Antistatic ceramic tiles ceramic tiles
GB / T 26825-2011 antistatic anticorrosive plastic
GB 50515-2010 guide （anti）-static floor design specifications
GB 50611-2010 antistatic electronic engineering design specifications
GJB 105-1998-Z electronic products against electrostatic discharge control manual
GJB 3007A-2009 anti-static work area technical requirements
GJB 5104-2004 Radio Fuze hood hood with anti-static coating and electrostatic properties General requirements
Fourth, the volume resistivity Surface resistivity tester technical indicators
1 resistance measurement range: 1 × 104Ω ~ 1 × 1018Ω, divided into ten range.
2 current measurement range of 2 × 10-4A ~ 1 × 10-16A
3 all-digital LCD display.
4 Accuracy: Accuracy is better than the following table:
Effective Range Display range 20 ~ 30 ℃ RH <80%
104 0.01 19.99 1%
105 0.01 19.99 1%
106 0.01 19.99 1%
107 0.01 19.99 1%
108 0.01 19.99 1%
109 0.01 19.99 1%
1010 from 0.01 to 19.99 5% +2 digits
1011 from 0.01 to 19.99 5% +2 digits
1012 from 0.01 to 19.99 5% +5 d
1013 0.01 19.99 10% +5 d
1014 0.01 19.99 10% +5 d
1014 above 0.01 ~ 19.99 10-15% +5 word
（Outside the valid display range errors are likely to increase）
Test current the same accuracy and resistance）
Test voltage accuracy is 10%
5 Use environment: Temperature -10 ℃ ~ 50 ℃ Relative humidity <90%.
6 Test voltage: DC10V, 50V, 100V, 250V, 500V, 1000V. ± 10%
7-powered forms: AC 220V, 50HZ, power consumption of about 10W.
8 Instrument Size: 300mm × 280mm × 150 mm.
9 Weight: about 3.0KG.
Five, terminology
1） Insulation resistance: is applied to the sample in contact with the second electrode of the DC voltage is divided between the two electrodes by the quotient of the total current. It depends on the volume resistivity and surface resistivity.
2） Volume resistance: the sample is placed on two opposite surfaces of two electrodes a DC voltage applied between the two electrodes and the flow through the quotient between the steady-state current; the current does not include current along the surface of the material. Be formed between the two electrodes is negligible polarization.
3） Volume Resistivity: insulation material inside the electric field intensity of the steady state current density, that is the volume resistance per unit volume.
4） Surface resistance: a surface of the specimen of the applied voltage between the electrodes after a certain time and the flow of current between two electrodes of the quotient; the current flowing through the primary current of the sample surface, but also part of the flow through the sample volume of the current component. Between the two electrodes
Possible formation of polarization is negligible.
Surface Resistivity: The surface layer of the insulating material of the electric field strength of the current density and the line, that is the surface resistance per unit area.
Six, measurement technology
a. Typically, the insulating material for electrical insulation between the various parts of the system and the insulation, the solid insulation material also acts as a mechanical support function. Material is generally desirable to have as high insulation resistance, and has suitable mechanical, chemical and heat resistance.
b. insulating materials generally have a high resistivity, the conduction current is very small. If you pay attention to the interference of external factors and the leakage current, the measurement results will change a lot of errors. While the insulating material itself and the environmental conditions change absorbency measurement results
Fruit also have a great impact.
c. impact test volume resistivity and surface resistivity of the main factors are temperature and humidity, electric field strength, so the charging time and the residual charge. Volume resistivity of the insulating material can be used as a parameter selected, the resistivity changes with temperature and humidity changes significantly. Body
Measurement of volume resistivity is often used to check the insulation material is uniform, or to detect but which can affect the quality of the materials can not be detected by other means to conductive impurities.
d. because the volume resistivity is more or less always included in the test to the surface resistance, thus only approximate measure surface resistance measured surface resistance value can represent the test sample is the degree of surface contamination. Therefore, the surface resistivity of the material itself is not a Characterization
Characteristic parameters, but a characteristic of the material parameters of surface contamination. When the surface resistance is high, it is often time changes in an irregular manner. Measuring the surface resistance is usually specified time of 1min electrification.
（1） Temperature and humidity: solid insulating materials insulation resistance increases with temperature and humidity is reduced, in particular the volume resistivity change with temperature change is very large. Thus, porcelain material not only to determine the volume resistivity at room temperature, but also measuring temperature
The volume resistivity, in order to assess the quality of the insulation properties. Large conductivity of the water, as humidity increases, the surface resistivity and has open porosity volume resistivity of the electrical ceramic materials drastically. Therefore, the determination should be strictly in accordance with the provisions of sample handling requirements
And tested environmental conditions.
（2） electric field intensity: When the electric field intensity is relatively high, the mobility of ions increases with increasing electric field strength, and also close to breakdown a large number of electron mobility, the volume resistivity greatly reduced time. Therefore, the measurement time, the applied voltage should not exceed
Predetermined value.
（3） the residual charge: the sample processing and testing process, it may generate static electricity, the higher the resistance the more prone to static electricity, affect the measurement accuracy. Thus, in the measurement, the sample to compley discharge, several electrodes can be short-circuited together.
（4） the elimination of stray electric potential: the insulation resistance measuring circuit, there may be some stray electric potential, such as thermoelectric power, electrolysis potential, exposure potential, of which the greatest impact on the potential for the electrolysis. With high resistance meter to measure the surface moist sample volume resistance when measuring
Protected poles between pole and can produce 20mv potential. Before the test should be checked for stray electric potential. According to the sample before and after pressurization of the secondary impedance meter indicates whether the same to determine whether stray electric potential. If the same proven spurious electrical potential; otherwise should look for troubleshooting and miscellaneous
Scattered potential causes can be measured.
（5） to prevent leakage current: For high resistive material can be removed only by taking protection technology leakage current measurement. Protection technology that is caused by measurement errors in the placement of protective conductor leakage path, stopped may cause measurement errors stray current,
So that does not flow through the measuring circuit or meter. Protective conductor connected together to form the protected side, usually protected grounded. Measure the volume resistance, protection of highly three-electrode system is to protect the conductors. This requires the guard electrode and measuring the surface resistance between the electrodes is higher than the sample
A resistor element connected in parallel with it 10 to 100 times. Line connected, you should first check whether there leakage. At this point disconnect power lines connected with the specimen plus voltage. If the measurement sensitivity range, the measuring instrument indicates the resistance value is infinite, then the line leak
Power, can be measured.
（6） conditional processing requirements and test conditions: the resistance of solid insulating materials with temperature and humidity increases. Sample pretreatment conditions depend on the material being tested, these conditions in the material specification. Recommended GB10580 "solid insulating materials under test
Test before and the use of standard test conditions "specified in the pretreatment method. Using glycerol - water pretreatment humidity chamber for humidity. Test conditions shall be as consistent as possible with the pretreatment conditions, in some cases （such as flooding treatment） can not maintain the pretreatment conditions and measurement
Consistent test conditions should be removed from the pretreatment environment after completion of the test in the shortest possible time, usually no more than 5 minutes.
（7） The electrification time requirements: If the DC voltage is applied to the sample in contact with two electrodes, the current through the sample to be exponential decay to a stable value. Decrease in current over time may be due to dielectric polarization and the movable electrode due to ion displacement. For
Volume resistivity of the material is less than 1010Ω · m, the steady state is usually reached within 1 minute. Therefore, the time to go through this after electrochemical measurement resistor. For higher resistivity material, current decreases in the process may last for minutes, hours, days, due to
This requires a longer period of time electricity. If desired, the volume resistivity can be used to describe the relationship and the time characteristics of the material. When the surface resistance is high, it is often time changes in an irregular manner. Measurement of surface resistance are generally required one minute electrification time
.
Seven, volume resistivity Surface resistivity tester Caution:
Impedance measurement method must be used in strict accordance with Buju, otherwise it may cause permanent damage to the instrument or electrical people.
One should "Rx" zeroing when open at both ends connected to the resistor box or as measuring object when measured after zero will produce large errors. After zeroing in general once the test process without re-zero, but after changing the measurement voltage may have to re-zero.
2, prohibits the "Rx" short ends to avoid micro-current amplifier by the high current impulse
3, in the testing process should not arbitrarily change measure voltage, measure the voltage may be altered arbitrarily high voltage or current is too large damage the device under test or the test instruments, and some material is non-linear, ie, voltage and current is not consistent with Ohm law has changed
Alternating voltage is not linear due to the current change, so the measured resistance will change.
4, measured from the low-order profile and gradually pull toward a higher profile slightly reversed stay every 1 to 2 seconds to observe the display numbers, should be stopped when the displayed value, the current number of records that is, the measured resistance values. If "1", it indicates Underrange pull files should go higher. Until there was
Figures shown so far. When a show can not go down to the higher number allocated file, otherwise it may damage the instrument （the machine has over-current protection circuit）. In addition to 104 Ω stalls outside, when the display is less than 1.99, which means that over range should downshift!
5, most insulating materials, in particular anti-static material resistance value after the voltage there will be a number of changes caused by changes in the high resolution of the instrument, which will cause the end of the displayed value is changed by several orders, which not the instrument itself, but
Conductive object being measured is complex mechanism and makes some changes in resistance. In this case, the effective number often take two suffice.
6, after power, fingers can not touch the metal part of the high-voltage instrument has two roots line: high voltage （red） and micro-current test line. When used to pay attention to high-voltage lines, high voltage power future generations can not be touched in order to avoid electrical or hemp hand.
7, the test process can not touch the micro-micro-current test current test side by side fear or human induced voltage high current and electrostatic shocks. So in the boot and test process can not end in contact with the micro-current testing, in order to avoid damage to the instrument.
8, in the measurement of impedance should be used when the object to be measured shield shield box. In the measurement is greater than 1010 Ω or more, in order to prevent interference caused by reading unstable surface.
9, should be completed for each measurement range switch back to "104" file then the next test in the measuring range should gradually switch to high resistance range, the measurement range switch complete reversal should be low. To ensure that the next time you turn the range switch in the low resistance range file.
Body generally can bring thousands or even tens of thousands of volts electrostatic!
Eight, impedance measurement FAQs
1. Why is measuring the same object with different resistance ranges have different readings?
This is because the measurement of resistance in order to prevent over-voltage damage to the instrument, if there is over-range protection circuit inside the instrument to work, will test the voltage down to protect the inside amplifier. Measured at different voltages of the same object will have different results. And when measuring
If the resistance reading is less than 199, it is necessary only for the three-digit number and the first digit is 1, the accuracy to decline. Therefore, when measuring resistance when first reading becomes a reading from one, it should not go down to the higher range of the instrument caused by twisting the switch to prevent excessive current impulse
Blow. In actual use, the reading than the median number of bits less than the reading accuracy.
2. Why are some objects when the current measurement with different ranges measured results will appear larger difference?
This is because the general object is not a constant current output stream, and the instrument has a certain resistance, when the selected range on the instrument so that the resistance is too large voltage drop on the effect on the instrument when the output current of the measured object may cause measurement errors. Generally the smaller the current measuring range
The higher the resistance, so the current should be used in the measurement of large current range. In actual use, as long as a meter reading, the reading of the small number of bits less than the number of bits more accurate readings.
3. Why the measurement instrument reading is always unstable?
Generally the electric conductivity of the material is not critical as a standard sample in a certain voltage resistance are very stable under the current, there are many materials, especially anti-static material which does not comply with Ohm's law conductivity, so the readings instability in the measurement. This is not a problem of the instrument, but is
Measuring the performance of object decisions. Some standard requirements to measure 1 minute readings shall prevail. Usually in the measurement of high resistance or micro-current measurement accuracy because of the poor reproducibility of the measurement reading only require 2 or 3. Also in measuring large resistances if the shield is not
Good also due to external electromagnetic signal measuring instrument readings resulting instability.
4 This is because when the measured object and the measuring instrument has a certain input capacitance of this capacitor has been charged in the measurement to the measuring resistor the voltage value if the instrument does not turn off the power after the block 104 to position the charged The capacitor will instrument amplifier
Discharge caused by damage to the instrument. When the object being measured capacitance increases, the test voltage is higher, the greater the energy storage capacitors, more prone to damage the instrument, particularly in the high resistance range or low range when the current is very sensitive because of the instrument, the instrument overload damage
More likely. So be sure to dial to 104 gear range switch off the power before.
5. Why not change during the measuring resistance on the analyte test voltage?
If in the process of measuring the resistance to change on the analyte test voltage, regardless of the voltage becomes high or low when they will produce a large pulse current, the large current is likely to make the instrument over range or even damage the instrument. Other hand, if the sudden change in voltage will be through
The measured object （distribution） or reverse discharge capacitor discharge impact on the measurement instrument and damage equipment. Some objects of the pressure is low, when you have the right to change the voltage measurements can penetrate and produce high currents damage the instrument. If you want to change the measurement voltage, ensure that
Measuring object will not breakdown voltage is too high, the first switch 104 stalls will range after the power is turned off again from the instrument panel to adjust to the required voltage. Some materials are non-linear, voltage and current that is incompatible with the Ohm's law, the voltage is changed due to
Current change is not linear, so the measured resistance will change.
6. Why do you want to measure the complete range switch dial to 104 files after power off?
This is because the machine capacitor charged with a high voltage （maximum voltage of 1200V or more）, the power carried by these capacitors maintain a longer period of time, if you turn off the power switch, it will be quickly inside the high-voltage capacitor discharge , and not in the high-pressure side measuring
Leaving very dangerous voltages cause electrical shock. If only the dial instead of the power cord off the power at the beginning, although off the power supply, but also inside the machine due to prolonged high-voltage capacitors maintain high voltage, will be on staff or other objects cause electric shock or damage. The instrument in question
Do not open the case when the machine due to the high
Pressure cause an electric shock, the instrument is to find a professional technician or return to factory repair.
Nine, volume resistivity Surface resistivity tester main applications
impedance test measures a material such as Static （anti-static shoes, anti-static plastics and rubber products, anti-static floor computer room, etc.） resistance testing;
b Material Volume resistivity （rate） and surface resistivity （rate） measurements;
c electrochemistry and materials testing, as well as physics, optics and materials research;
d weak current measurement devices such as the photoelectric effect and dark current measurements.
Additional description:
Resistivity
Resistivity is used to indicate the physical resistance characteristics of various substances. Some material 1 meter long, cross-sectional area of ??1 square millimeter at room temperature （20 ℃ pm） resistance of the wire, called the resistivity of the material. Resistivity is measured in ohm-meters （Ω · m or
ohmm）, commonly used unit is ohm-mm and ohm meter.
Application
Lower resistivity material is called a conductor, the common conductor is the main metal, and the conductive nature best silver, followed by the semiconductor, silicon-germanium. When there is an external electric field, the metal in the movement of free electrons and lattice nodes constantly hot vibrator is made from
Collide with the child, so that electron movement hindered, thus it has a certain resistance. Other conductive materials easily such as glass, rubber, etc., high resistivity, commonly referred to as an insulator. Between the material between the conductor and the insulator （such as silicon） called semiconductors. Resistivity
Science symbol ρ （Rho）. The resistance of the object is known, by resistivity ρ, length l and cross-sectional area A calculated: ρ = RA / I, in the formula, the resistance R in ohms, the length l in meters, cross-sectional area A in square meters, unit of resistivity ρ
Ohm-m
The formula
Resistivity is calculated as: ρ = RS / L
ρ is the resistivity - common units Ω · m
S is the cross-sectional area - common units ㎡
R is the resistance value - common units Ω
L is the length of the wire - common in m
-----------------------------------------
Another resistivity is calculated as: ρ = E / J
ρ is the resistivity - common units Ω · mm2 / m [1]
E is the electric field strength - Common units N / C
J is the current density - Common units A / m
（E, J be the vector）
Explanation
1. And the conductor resistivity ρ of the material only, but also on the temperature and the conductor. Little change in the temperature range: Almost all metals resistivity changes linearly with temperature, that is ρ = ρo （1 + at）. Where t is the Celsius temperature, ρo is the resistivity O ℃, a
Is the temperature coefficient of resistivity.
2. Since the resistance change with temperature change, so for some electrical resistance, which must indicate their physical state. If a 220 V -100 W lamp filament resistance is 484 ohms when power is not energized only 40 ohms.
3. Resistivity and resistance are two different concepts. Resistivity material on the current hindered reflect the attributes of objects on the current resistance is hindered reflecting properties.
Summary:
Under normal （from the table） in order, the best conductivity of silver, copper, aluminum, which is the most common three materials, often used as a conductor, of which the most widely used in the copper, the wires are now almost Copper （precision instruments, except for special occasions） aluminum due
Chemically unstable prone to oxidation has been eliminated. Because aluminum density, drawn wide, and the price cheaper than copper, is now widely used in power transmission system overhead electricity transmission lines. In order to solve insufficient rigidity aluminum defects, generally ACSR, namely
Aluminum wire coated with an internal steel wire to improve strength. Silver conductive best performance, but because of the high cost of rarely used, and only in high demand situations was only used, such as precision instruments, high-frequency oscillator, aerospace and so on. By the way gold contacts on the instrument in some cases
Also useful for gold, it is because gold is chemically stable so the use of, not because of its small resistivity due.
Beijing North Canton Precision Instrument Co., Ltd. Hot products:
（Plastic and Electric Performance Series） voltage breakdown tester, electrical strength tester, dielectric breakdown strength tester, electronic universal testing machine, surface resistivity tester volume resistivity, dielectric constant and dielectric loss tester, leakage Tracking tester, horizontal vertical
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Service and Warranty:
Over the years, our company has been specializing in the production of electrical test equipment, through research, exploration, summed up a complete product service support system, to provide users with high-quality and timely pre-sales, after-sales service
To create brand, enhance their visibility and establish a corporate image, our spirit of "all the pursuit of quality, customer satisfaction for the purpose of" spirit, "the most preferential prices, the most attentive service, the most reliable product quality" principle You solemn promise:
A commitment to product quality:
1, I need to provide to ensure that the original production equipment, and factory data accessories complete. In order to maintain the normal operation of the contract and maintenance of equipment, I guarantee to provide technical information and drawings are complete, clear and correct.
2, product manufacturing and testing are quality records and test data.
3, the product performance testing, we sincerely invite users to visit the product of the whole process, all performance checks, was confirmed to be eligible after the boxed product shipped.
Second, the product price promise:
1, in order to ensure high reliability and advanced systems were chosen selection of quality brand-name domestic or international.
2, in the same competitive conditions, our company not to reduce product performance, change the product on the basis of the cost of parts, in good faith in the most favorable price to your side.
Three: installation, commissioning and acceptance of commitments:
1, to assist with the installation, responsible for equipment transport and commissioning.
2, the device according to order technical annex for acceptance. Final acceptance for the purchaser, the user-supplied samples to test and provide test reports.
3, installation and commissioning while operating the instrument off-site training of operators free 2-3, the operator should be selected by the demand side of the long-term stability of staff training to the basic principles of the equipment, software, use, operation, maintenance matter of understanding and application of the
Devices are able to operate independently of the sample detection, analysis, and can carry out basic maintenance.
Fourth, warranty:
1, the device year warranty and lifetime service within one year of non-human damaged parts replaced free of charge during the warranty period the user received an invitation, at the latest within a response time of 2 hours, after the failure with user confirmation, I will 48 hours to send engineers arrived at the scene
Free service as soon as possible to identify the fault location and cause of the malfunction, failure to promptly report the reasons for users and exclusion methods.
2, man-made damaged parts during the warranty period by purchasing （processing） prices charged replacement.
3, the warranty period to continue to provide users with high-quality technical services, the user received within 3 days after repair invited to send engineers to reach users on-site repair. And enjoy the preferential treatment of purchased parts.
4, the sensor and the whole circuit overload overpressure damage is not covered under warranty.
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