【萬用(yong)(yong)表(biao)測電(dian)(dian)容(rong)】萬用(yong)(yong)表(biao)怎么(me)測電(dian)(dian)容(rong) 怎樣用(yong)(yong)萬用(yong)(yong)表(biao)測電(dian)(dian)容(rong)

現在，數(shu)(shu)字式(shi)測量儀(yi)表(biao)(biao)已成為主流，有取代模(mo)擬式(shi)儀(yi)表(biao)(biao)的趨勢。與模(mo)擬式(shi)儀(yi)表(biao)(biao)相比(bi)，數(shu)(shu)字式(shi)儀(yi)表(biao)(biao)靈(ling)敏(min)度高，準確度高，顯示(shi)清晰，過載能力強，便于攜帶(dai)，使用(yong)(yong)更簡單。下面以VC9802型數(shu)(shu)字萬用(yong)(yong)表(biao)(biao)為例，簡單介紹其使用(yong)(yong)方法。

1、使用方法

（1）使用前，應認真閱讀有關的使用說明書，熟悉(xi)電(dian)源(yuan)開關、量程開關、插(cha)孔、特(te)殊插(cha)口的作用。

（2）將電(dian)源開關置于ON位置。

（3）交直(zhi)流(liu)電壓的(de)(de)測量：根(gen)據需要將量程(cheng)開關撥(bo)至DCV（直(zhi)流(liu)）或(huo)ACV（交流(liu)）的(de)(de)合(he)適(shi)量程(cheng)，紅表筆插入(ru)(ru)V／Ω孔，黑表筆插入(ru)(ru)COM孔，并(bing)將表筆與被測線路并(bing)聯，讀數即顯示。

（4）交直流電流的(de)測(ce)(ce)量(liang)：將(jiang)量(liang)程開(kai)關撥至DCA（直流）或(huo)ACA（交流）的(de)合適量(liang)程，紅表(biao)筆(bi)插入mA孔(kong)(kong)（＜200mA時）或(huo)10A孔(kong)(kong)（＞200mA時）,黑表(biao)筆(bi)插入COM孔(kong)(kong)，并(bing)將(jiang)萬用表(biao)串(chuan)聯(lian)在被測(ce)(ce)電路中即(ji)可。測(ce)(ce)量(liang)直流量(liang)時，數(shu)字(zi)萬用表(biao)能自動顯示極(ji)性。

（5）電(dian)(dian)(dian)(dian)阻(zu)(zu)的(de)(de)測量(liang)(liang)(liang)(liang)：將量(liang)(liang)(liang)(liang)程(cheng)開(kai)關(guan)撥至Ω的(de)(de)合適量(liang)(liang)(liang)(liang)程(cheng)，紅表(biao)筆插入V／Ω孔(kong)，黑表(biao)筆插入COM孔(kong)。如果(guo)被測電(dian)(dian)(dian)(dian)阻(zu)(zu)值超出所選(xuan)擇(ze)量(liang)(liang)(liang)(liang)程(cheng)的(de)(de)最大值，萬用表(biao)將顯示“1”，這(zhe)時應選(xuan)擇(ze)更高的(de)(de)量(liang)(liang)(liang)(liang)程(cheng)。測量(liang)(liang)(liang)(liang)電(dian)(dian)(dian)(dian)阻(zu)(zu)時，紅表(biao)筆為(wei)正極，黑表(biao)筆為(wei)負極，這(zhe)與指針式萬用表(biao)正好相反。因此，測量(liang)(liang)(liang)(liang)晶體管、電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容器等有極性的(de)(de)元器件時，必須注意(yi)表(biao)筆的(de)(de)極性。

2、使用注意事項

（1）如果無法預先估計被測電(dian)壓(ya)或電(dian)流(liu)的大小(xiao)，則應先撥(bo)至最(zui)高(gao)量(liang)程擋測量(liang)一次，再視情況逐漸把量(liang)程減小(xiao)到合適位置。測量(liang)完畢，應將量(liang)程開關(guan)撥(bo)到最(zui)高(gao)電(dian)壓(ya)擋，并關(guan)閉電(dian)源。

（2）滿量(liang)程時(shi)(shi)，儀表僅在最高位顯示數字(zi)“1”，其它(ta)位均消(xiao)失，這時(shi)(shi)應選擇更高的(de)量(liang)程。

（3）測(ce)量電(dian)壓(ya)時，應(ying)將數字(zi)萬(wan)用表與被測(ce)電(dian)路(lu)并聯(lian)。測(ce)電(dian)流(liu)時應(ying)與被測(ce)電(dian)路(lu)串聯(lian)，測(ce)直流(liu)量時不(bu)必考慮(lv)正、負極性(xing)。

（4）當誤用交流電(dian)壓(ya)(ya)(ya)擋(dang)(dang)去測量(liang)直流電(dian)壓(ya)(ya)(ya)，或者誤用直流電(dian)壓(ya)(ya)(ya)擋(dang)(dang)去測量(liang)交流電(dian)壓(ya)(ya)(ya)時，顯(xian)示(shi)屏將(jiang)顯(xian)示(shi)“000”，或低(di)位(wei)上(shang)的數字(zi)出現跳動(dong)。

（5）禁(jin)止(zhi)在測(ce)量高電壓（220V以(yi)上(shang)(shang)）或大電流（0.5A以(yi)上(shang)(shang)）時換量程，以(yi)防止(zhi)產生電弧，燒毀開關觸點。

（6）當顯示“”、“BATT”或“LOWBAT”時，表示電池的電壓低于工作電壓。

怎樣用萬用表測電容可按以下方法進行：

1、用電容檔直接檢測

某些數字萬用表(biao)具有測(ce)量電容(rong)(rong)的功能，其量程(cheng)分(fen)為2000p、20n、200n、2μ和20μ五(wu)檔。測(ce)量時可將(jiang)已放電的電容(rong)(rong)兩引腳(jiao)直(zhi)接(jie)插入表(biao)板上(shang)的Cx插孔(kong)，選取適(shi)當的量程(cheng)后(hou)就(jiu)可讀取顯示數據。

000p檔，宜(yi)于測量(liang)小于2000pF的電(dian)容(rong)(rong)；20n檔，宜(yi)于測量(liang)2000pF至(zhi)(zhi)20nF之間(jian)的電(dian)容(rong)(rong)；200n檔，宜(yi)于測量(liang)20nF至(zhi)(zhi)200nF之間(jian)的電(dian)容(rong)(rong)；2μ檔，宜(yi)于測量(liang)200nF至(zhi)(zhi)2μF之間(jian)的電(dian)容(rong)(rong)；20μ檔，宜(yi)于測量(liang)2μF至(zhi)(zhi)20μF之間(jian)的電(dian)容(rong)(rong)。

經(jing)驗證明，有(you)些型號的數(shu)(shu)字萬(wan)用表(biao)（例(li)如DT890B＋）在測(ce)量(liang)50pF以下的小容(rong)(rong)(rong)(rong)量(liang)電(dian)(dian)容(rong)(rong)(rong)(rong)器(qi)時誤差較大，測(ce)量(liang)20pF以下電(dian)(dian)容(rong)(rong)(rong)(rong)幾乎(hu)沒有(you)參(can)考價值。此(ci)時可采用串聯法測(ce)量(liang)小值電(dian)(dian)容(rong)(rong)(rong)(rong)。方法是：先找一只220pF左右的電(dian)(dian)容(rong)(rong)(rong)(rong)，用數(shu)(shu)字萬(wan)用表(biao)測(ce)出其(qi)實際容(rong)(rong)(rong)(rong)量(liang)C1，然后把待測(ce)小電(dian)(dian)容(rong)(rong)(rong)(rong)與之并聯測(ce)出其(qi)總(zong)容(rong)(rong)(rong)(rong)量(liang)C2，則兩者之差（C1－C2）即是待測(ce)小電(dian)(dian)容(rong)(rong)(rong)(rong)的容(rong)(rong)(rong)(rong)量(liang)。用此(ci)法測(ce)量(liang)1～20pF的小容(rong)(rong)(rong)(rong)量(liang)電(dian)(dian)容(rong)(rong)(rong)(rong)很準(zhun)確(que)。

2、用電阻檔檢測

實踐證明，利用(yong)數(shu)(shu)字(zi)萬用(yong)表(biao)(biao)也可觀察(cha)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)的(de)(de)充電(dian)(dian)(dian)(dian)(dian)過程，這實際(ji)上是(shi)以(yi)離散的(de)(de)數(shu)(shu)字(zi)量反(fan)映充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)的(de)(de)變化情(qing)況。設數(shu)(shu)字(zi)萬用(yong)表(biao)(biao)的(de)(de)測(ce)(ce)量速率為n次/秒，則在觀察(cha)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)的(de)(de)充電(dian)(dian)(dian)(dian)(dian)過程中，每秒鐘(zhong)即(ji)可看到n個彼(bi)此(ci)獨(du)立且依次增大(da)的(de)(de)讀數(shu)(shu)。根據數(shu)(shu)字(zi)萬用(yong)表(biao)(biao)的(de)(de)這一顯示特點，可以(yi)檢測(ce)(ce)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)的(de)(de)好(hao)壞(huai)和估測(ce)(ce)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)量的(de)(de)大(da)小。下(xia)面介(jie)紹的(de)(de)是(shi)使用(yong)數(shu)(shu)字(zi)萬用(yong)表(biao)(biao)電(dian)(dian)(dian)(dian)(dian)阻檔檢測(ce)(ce)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)的(de)(de)方法(fa)，對于(yu)未設置電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)檔的(de)(de)儀表(biao)(biao)很(hen)有實用(yong)價值。此(ci)方法(fa)適用(yong)于(yu)測(ce)(ce)量0.1μF～幾千微法(fa)的(de)(de)大(da)容(rong)(rong)量電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)。

將(jiang)數字萬用表撥(bo)至合適的電(dian)(dian)阻(zu)檔，紅表筆(bi)和黑(hei)表筆(bi)分別(bie)接觸被測電(dian)(dian)容器(qi)Cx的兩(liang)極，這時(shi)顯(xian)示(shi)(shi)值(zhi)將(jiang)從(cong)“000”開始(shi)逐漸(jian)增加，直至顯(xian)示(shi)(shi)溢(yi)出符號“1”。若始(shi)終顯(xian)示(shi)(shi)“000”，說(shuo)明(ming)電(dian)(dian)容器(qi)內部(bu)短路；若始(shi)終顯(xian)示(shi)(shi)溢(yi)出，則(ze)可(ke)能(neng)時(shi)電(dian)(dian)容器(qi)內部(bu)極間開路，也可(ke)能(neng)時(shi)所(suo)選擇的電(dian)(dian)阻(zu)檔不合適。檢查電(dian)(dian)解電(dian)(dian)容器(qi)時(shi)需要注意，紅表筆(bi)（帶正電(dian)(dian)）接電(dian)(dian)容器(qi)正極，黑(hei)表筆(bi)接電(dian)(dian)容器(qi)負極。