電(dian)子(zi)(zi)設備(bei)中使(shi)用著大量各種類型(xing)的電(dian)子(zi)(zi)元器(qi)件(jian)，設備(bei)發生(sheng)故障大多是由于電(dian)子(zi)(zi)元器(qi)件(jian)失(shi)效或損壞(huai)引起的。因(yin)此(ci)怎么(me)正(zheng)確檢測電(dian)子(zi)(zi)元器(qi)件(jian)就顯(xian)得(de)尤其重要，這也是電(dian)子(zi)(zi)維修人員(yuan)必須掌握的技(ji)能。下面是部分(fen)常見電(dian)子(zi)(zi)元器(qi)件(jian)檢測經驗和技(ji)巧，供大家(jia)參(can)考。
1．測(ce)整流電橋各腳的極性
萬用表置R×1k擋，黑(hei)表筆(bi)(bi)(bi)接(jie)橋(qiao)堆的任(ren)意(yi)引(yin)腳(jiao)(jiao)，紅表筆(bi)(bi)(bi)先后測其余三只腳(jiao)(jiao)，如果讀(du)數均(jun)為(wei)無(wu)窮大(da)，則(ze)黑(hei)表筆(bi)(bi)(bi)所接(jie)為(wei)橋(qiao)堆的輸(shu)出(chu)正極(ji)，如果讀(du)數為(wei)4～10kΩ，則(ze)黑(hei)表筆(bi)(bi)(bi)所接(jie)引(yin)腳(jiao)(jiao)為(wei)橋(qiao)堆的輸(shu)出(chu)負極(ji)，其余的兩引(yin)腳(jiao)(jiao)為(wei)橋(qiao)堆的交(jiao)流(liu)輸(shu)入端(duan)。
2．判(pan)斷晶振的(de)好壞
先用萬用表(R×10k擋)測晶(jing)振(zhen)兩端的電(dian)(dian)阻值，若為無窮大，說明(ming)晶(jing)振(zhen)無短路或漏電(dian)(dian)；再將試電(dian)(dian)筆(bi)插(cha)入市電(dian)(dian)插(cha)孔內，用手(shou)指(zhi)捏住(zhu)晶(jing)振(zhen)的任一(yi)引(yin)腳(jiao)，將另一(yi)引(yin)腳(jiao)碰觸試電(dian)(dian)筆(bi)頂端的金屬部分，若試電(dian)(dian)筆(bi)氖泡發紅，說明(ming)晶(jing)振(zhen)是好的；若氖泡不亮，則說明(ming)晶(jing)振(zhen)損(sun)壞。
3．單向晶閘管(guan)檢測
可用萬用表的(de)(de)R×1k或(huo)R×100擋測(ce)(ce)(ce)量(liang)任意兩極(ji)(ji)(ji)(ji)之(zhi)問的(de)(de)正(zheng)、反向(xiang)電阻(zu)，如(ru)果(guo)找到一(yi)對極(ji)(ji)(ji)(ji)的(de)(de)電阻(zu)為(wei)低阻(zu)值(zhi)(100Ω～lkΩ)，則此時(shi)(shi)黑表筆所接的(de)(de)為(wei)控制(zhi)極(ji)(ji)(ji)(ji)，紅(hong)表筆所接為(wei)陰極(ji)(ji)(ji)(ji)，另一(yi)個極(ji)(ji)(ji)(ji)為(wei)陽極(ji)(ji)(ji)(ji)。晶閘管共有3個PN結，我們可以通過測(ce)(ce)(ce)量(liang)PN結正(zheng)、反向(xiang)電阻(zu)的(de)(de)大(da)小來判別它(ta)的(de)(de)好壞。測(ce)(ce)(ce)量(liang)控制(zhi)極(ji)(ji)(ji)(ji)(G)與陰極(ji)(ji)(ji)(ji)[C)之(zhi)間(jian)的(de)(de)電阻(zu)時(shi)(shi)，如(ru)果(guo)正(zheng)、反向(xiang)電阻(zu)均為(wei)零或(huo)無窮大(da)，表明控制(zhi)極(ji)(ji)(ji)(ji)短路(lu)或(huo)斷路(lu)；測(ce)(ce)(ce)量(liang)控制(zhi)極(ji)(ji)(ji)(ji)(G)與陽極(ji)(ji)(ji)(ji)(A)之(zhi)間(jian)的(de)(de)電阻(zu)時(shi)(shi)，正(zheng)、反向(xiang)電阻(zu)讀數均應很(hen)大(da)；
{測量陽極(ji)(A)與陰極(ji)(C)之間的電阻時，正、反向電阻都應很(hen)大。
4．雙(shuang)向晶閘管的極性(xing)識(shi)別
雙向(xiang)晶(jing)閘管(guan)有主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)1、主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)2和控(kong)制(zhi)(zhi)極(ji)(ji)(ji)，如(ru)果用萬用表(biao)(biao)R×1k擋測量(liang)(liang)兩個(ge)主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)之間的電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，讀數應近似無窮(qiong)大(da)，而控(kong)制(zhi)(zhi)極(ji)(ji)(ji)與任一(yi)個(ge)主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)之間的正、反向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)讀數只(zhi)有幾十歐。根據這一(yi)特性，我們(men)很(hen)(hen)容(rong)易通(tong)(tong)過(guo)測量(liang)(liang)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)之間電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)大(da)小(xiao)，識別出雙向(xiang)晶(jing)閘管(guan)的控(kong)制(zhi)(zhi)極(ji)(ji)(ji)。而當(dang)黑表(biao)(biao)筆接主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)1。紅表(biao)(biao)筆接控(kong)制(zhi)(zhi)極(ji)(ji)(ji)時所(suo)測得的正向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)總(zong)是要比反向(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)小(xiao)一(yi)些，據此我們(men)也很(hen)(hen)容(rong)易通(tong)(tong)過(guo)測量(liang)(liang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)大(da)小(xiao)來識別主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)1和主(zhu)(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)2。
5．檢查發光數(shu)碼管的好壞
先將(jiang)萬用表置(zhi)R×10k或R×l00k擋，然后(hou)將(jiang)紅(hong)表筆與(yu)數碼管(guan)(以共陰數碼管(guan)為例(li))的(de)“地”引出端相(xiang)連，黑表筆依次接數碼管(guan)其(qi)他引出端，七段(duan)均應分別(bie)發光，否則(ze)說明數碼管(guan)損(sun)壞。
6．判別結型場(chang)效應管的電(dian)極
將(jiang)(jiang)萬用表(biao)置于(yu)R×1k擋，用黑(hei)(hei)表(biao)筆(bi)(bi)接觸(chu)(chu)假定為柵極(ji)G的(de)管(guan)腳，然后用紅表(biao)筆(bi)(bi)分別接觸(chu)(chu)另外兩個(ge)管(guan)腳，若阻值(zhi)(zhi)均(jun)比較小(xiao)(5～10 Ω)，再將(jiang)(jiang)紅、黑(hei)(hei)表(biao)筆(bi)(bi)交(jiao)換測量一次。如阻值(zhi)(zhi)均(jun)大(∞)，說(shuo)明(ming)都是(shi)反向(xiang)電(dian)阻(PN結反向(xiang))，屬N溝(gou)道(dao)管(guan)，且(qie)黑(hei)(hei)表(biao)筆(bi)(bi)接觸(chu)(chu)的(de)管(guan)腳為柵極(ji)G，并說(shuo)明(ming)原先假定是(shi)正(zheng)(zheng)確的(de)。若再次測量的(de)阻值(zhi)(zhi)均(jun)很小(xiao)，說(shuo)明(ming)是(shi)正(zheng)(zheng)向(xiang)電(dian)阻，屬于(yu)P溝(gou)道(dao)場效應管(guan)，黑(hei)(hei)表(biao)筆(bi)(bi)所接的(de)也是(shi)柵極(ji)G。若不(bu)出現上(shang)述(shu)情(qing)況，可以(yi)調換紅、黑(hei)(hei)表(biao)筆(bi)(bi)，按上(shang)述(shu)方法進行測試，直至(zhi)判斷出柵極(ji)為止。一般結型場效應管(guan)的(de)源極(ji)與(yu)漏極(ji)在制造(zao)時是(shi)對(dui)稱的(de)，所以(yi)，當柵極(ji)G確定以(yi)后，對(dui)于(yu)源極(ji)S、漏極(ji)D不(bu)一定要判別，因為這兩個(ge)極(ji)可以(yi)互換使用。源極(ji)與(yu)漏極(ji)之(zhi)間的(de)電(dian)阻為幾千歐。
7．三極管電極的判別
對于一(yi)只型號標(biao)(biao)示不(bu)清(qing)或(huo)無標(biao)(biao)志的(de)三(san)極(ji)管(guan)，要想(xiang)分辨出(chu)它(ta)們的(de)三(san)個電(dian)(dian)極(ji)，也可用(yong)(yong)萬用(yong)(yong)表測(ce)試。先將萬用(yong)(yong)表量程開關撥(bo)在(zai)R×100或(huo)R×1k電(dian)(dian)阻(zu)擋(dang)上。紅(hong)表筆任意接(jie)(jie)觸(chu)(chu)三(san)極(ji)管(guan)的(de)一(yi)個電(dian)(dian)極(ji)，黑表筆依次接(jie)(jie)觸(chu)(chu)另外兩個電(dian)(dian)極(ji)，分別測(ce)量它(ta)們之間的(de)電(dian)(dian)阻(zu)值(zhi)，若測(ce)出(chu)均為(wei)(wei)幾百(bai)歐低(di)電(dian)(dian)阻(zu)時(shi)，則(ze)紅(hong)表筆接(jie)(jie)觸(chu)(chu)的(de)電(dian)(dian)極(ji)為(wei)(wei)基(ji)極(ji)b，此管(guan)為(wei)(wei)PNP管(guan)。若測(ce)出(chu)均為(wei)(wei)幾十(shi)至上百(bai)千歐的(de)高電(dian)(dian)阻(zu)時(shi)，則(ze)紅(hong)表筆接(jie)(jie)觸(chu)(chu)的(de)電(dian)(dian)極(ji)也為(wei)(wei)基(ji)極(ji)b，此管(guan)為(wei)(wei)NPN管(guan)。
在判別出(chu)管型和基極(ji)(ji)(ji)(ji)(ji)b的(de)(de)基礎上，利用三極(ji)(ji)(ji)(ji)(ji)管正(zheng)向電(dian)(dian)流放大系數比(bi)反向電(dian)(dian)流放大系數大的(de)(de)原理確定(ding)集(ji)(ji)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)。任意假定(ding)一(yi)個(ge)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)為(wei)c極(ji)(ji)(ji)(ji)(ji)，另一(yi)個(ge)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)為(wei)e極(ji)(ji)(ji)(ji)(ji)。將萬用表(biao)(biao)量程開關撥在R×1k電(dian)(dian)阻(zu)(zu)擋上。對(dui)(dui)于(yu)：PNP管，令紅表(biao)(biao)筆接c極(ji)(ji)(ji)(ji)(ji)，黑(hei)表(biao)(biao)筆接e極(ji)(ji)(ji)(ji)(ji)，再(zai)用手同時捏(nie)一(yi)下管子(zi)的(de)(de)b、c極(ji)(ji)(ji)(ji)(ji)，但不能(neng)使b、c兩(liang)極(ji)(ji)(ji)(ji)(ji)直(zhi)接相(xiang)碰，測出(chu)某一(yi)阻(zu)(zu)值。然后(hou)兩(liang)表(biao)(biao)筆對(dui)(dui)調進行第二次測量，將兩(liang)次測的(de)(de)電(dian)(dian)阻(zu)(zu)相(xiang)比(bi)較，對(dui)(dui)于(yu)：PNP型管，阻(zu)(zu)值小(xiao)的(de)(de)一(yi)次，紅表(biao)(biao)筆所(suo)接的(de)(de)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)為(wei)集(ji)(ji)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)。對(dui)(dui)于(yu)NPN型管阻(zu)(zu)值小(xiao)的(de)(de)一(yi)次，黑(hei)表(biao)(biao)筆所(suo)接的(de)(de)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)為(wei)集(ji)(ji)電(dian)(dian)極(ji)(ji)(ji)(ji)(ji)。
8．電(dian)位器的好(hao)壞判(pan)別
先測(ce)電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)標稱(cheng)阻值(zhi)(zhi)。用(yong)(yong)(yong)萬(wan)用(yong)(yong)(yong)表(biao)(biao)的(de)(de)歐(ou)姆擋(dang)測(ce)“1”、“3”兩(liang)端(設(she)“2”端為(wei)活(huo)動(dong)觸(chu)點)，其(qi)讀數應(ying)為(wei)電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)標稱(cheng)值(zhi)(zhi)，如萬(wan)用(yong)(yong)(yong)表(biao)(biao)的(de)(de)指針(zhen)不(bu)動(dong)、阻值(zhi)(zhi)不(bu)動(dong)或阻值(zhi)(zhi)相差很(hen)多，則(ze)表(biao)(biao)明該(gai)電(dian)(dian)位(wei)(wei)器(qi)已損壞。再檢查電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)活(huo)動(dong)臂與電(dian)(dian)阻片(pian)的(de)(de)接觸(chu)是(shi)否良(liang)好(hao)。用(yong)(yong)(yong)萬(wan)用(yong)(yong)(yong)表(biao)(biao)的(de)(de)歐(ou)姆擋(dang)測(ce)“1”、“2”或“2”、“3”兩(liang)端，將電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)轉軸按逆時針(zhen)方向旋至接近“關”的(de)(de)位(wei)(wei)置，此時電(dian)(dian)阻應(ying)越(yue)(yue)小(xiao)越(yue)(yue)好(hao)，再徐(xu)(xu)徐(xu)(xu)順時鐘旋轉軸柄(bing)，電(dian)(dian)阻應(ying)逐漸增(zeng)大，旋至極端位(wei)(wei)置時，阻值(zhi)(zhi)應(ying)接近電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)標稱(cheng)值(zhi)(zhi)。如在電(dian)(dian)位(wei)(wei)器(qi)的(de)(de)軸柄(bing)轉動(dong)過程中萬(wan)用(yong)(yong)(yong)表(biao)(biao)指針(zhen)有(you)跳動(dong)瑚象(xiang)，描踢活(huo)動(dong)觸(chu)』點接觸(chu)不(bu)良(liang)。
9．測量大(da)容(rong)量電(dian)容(rong)的漏電(dian)電(dian)阻
用(yong)500型萬用(yong)表置于R×10或R×100擋，待指(zhi)(zhi)針指(zhi)(zhi)向最大值時，再立即改用(yong)R×1k擋測(ce)量，指(zhi)(zhi)針會在(zai)較短時間內穩定(ding)，從而(er)讀出漏(lou)電(dian)(dian)電(dian)(dian)阻(zu)阻(zu)值。
10．判別(bie)紅外(wai)接(jie)收頭引腳(jiao)
萬(wan)用表(biao)(biao)(biao)置(zhi)R×1k擋，先(xian)假設接(jie)收(shou)頭(tou)的(de)(de)某腳(jiao)為(wei)接(jie)地端(duan)，將其(qi)與(yu)黑(hei)表(biao)(biao)(biao)筆相接(jie)，用紅表(biao)(biao)(biao)筆分別測量(liang)另兩(liang)腳(jiao)電(dian)阻(zu)，對(dui)比兩(liang)次所測阻(zu)值(一般(ban)在4～7k Q范(fan)圍)，電(dian)阻(zu)較(jiao)小的(de)(de)一次其(qi)紅表(biao)(biao)(biao)筆所接(jie)為(wei)+5V電(dian)源引(yin)腳(jiao)，另一阻(zu)值較(jiao)大的(de)(de)則為(wei)信(xin)(xin)號引(yin)腳(jiao)。反之(zhi)，若用紅表(biao)(biao)(biao)筆接(jie)已(yi)知(zhi)地腳(jiao)，黑(hei)表(biao)(biao)(biao)筆分別測已(yi)知(zhi)電(dian)源腳(jiao)及信(xin)(xin)號腳(jiao)，則阻(zu)值都在15kΩ以上(shang)，阻(zu)值小的(de)(de)引(yin)腳(jiao)為(wei)+5V端(duan)，阻(zu)值偏大的(de)(de)引(yin)腳(jiao)為(wei)信(xin)(xin)號端(duan)。如果測量(liang)結果符合上(shang)述(shu)阻(zu)值則可判(pan)斷(duan)該(gai)接(jie)收(shou)頭(tou)完好。
11．判斷無符號電解電容極性
先將電(dian)容短路(lu)放電(dian)，再將兩引線做(zuo)好A、B標記(ji)，萬用(yong)表(biao)置(zhi)R×100或R×1k擋，黑表(biao)筆接A引線，紅表(biao)筆接B引線，待指針靜(jing)止(zhi)不動(dong)后(hou)讀數，測完后(hou)短路(lu)放電(dian)；再將黑表(biao)筆接B引線，紅表(biao)筆接A引線，比較兩次讀數，阻值(zhi)較大的一次黑表(biao)筆所(suo)接為正極，紅表(biao)筆所(suo)接為負極。
12．測發光(guang)二(er)極管
取(qu)一(yi)個(ge)容(rong)(rong)(rong)量大于(yu)100“F的電解電容(rong)(rong)(rong)器(容(rong)(rong)(rong)量越大，現(xian)象越明顯)，先(xian)用萬(wan)用表(biao)(biao)(biao)(biao)R×100擋對其(qi)充電，黑(hei)(hei)表(biao)(biao)(biao)(biao)筆(bi)接(jie)(jie)電容(rong)(rong)(rong)正極(ji)(ji)(ji)，紅(hong)(hong)表(biao)(biao)(biao)(biao)筆(bi)接(jie)(jie)負極(ji)(ji)(ji)，充電完(wan)畢后(hou)，黑(hei)(hei)表(biao)(biao)(biao)(biao)筆(bi)改(gai)接(jie)(jie)電容(rong)(rong)(rong)負極(ji)(ji)(ji)，將(jiang)被測(ce)發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)接(jie)(jie)于(yu)紅(hong)(hong)表(biao)(biao)(biao)(biao)筆(bi)和(he)電容(rong)(rong)(rong)正極(ji)(ji)(ji)之間。如果發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)亮后(hou)逐(zhu)漸熄滅，表(biao)(biao)(biao)(biao)明它是(shi)好的。此時紅(hong)(hong)表(biao)(biao)(biao)(biao)筆(bi)接(jie)(jie)的是(shi)發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)的負極(ji)(ji)(ji)，電容(rong)(rong)(rong)正極(ji)(ji)(ji)接(jie)(jie)的是(shi)發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)的正極(ji)(ji)(ji)。如果發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)不亮，將(jiang)其(qi)兩端對調重新接(jie)(jie)上測(ce)試，還不亮，表(biao)(biao)(biao)(biao)明發(fa)(fa)光(guang)(guang)二極(ji)(ji)(ji)管(guan)已損(sun)壞。
13.光(guang)電耦合器檢測
萬用表選(xuan)用電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R×100擋(dang)(dang)，不得選(xuan)R×10k擋(dang)(dang)，以防電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓過高(gao)擊穿(chuan)發光(guang)二(er)極管(guan)(guan)。紅(hong)、黑表筆(bi)(bi)接輸(shu)入端，測正(zheng)、反(fan)向(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，正(zheng)常(chang)(chang)時(shi)正(zheng)向(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)為(wei)數十(shi)歐姆，反(fan)向(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)幾千歐至幾十(shi)千歐。若(ruo)正(zheng)、反(fan)向(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)相近，表明發光(guang)二(er)極管(guan)(guan)已損壞(huai)。萬用表選(xuan)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R×1擋(dang)(dang)。紅(hong)、黑表筆(bi)(bi)接輸(shu)出端，測正(zheng)、反(fan)向(xiang)(xiang)(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，正(zheng)常(chang)(chang)時(shi)均接近于∞，否則受(shou)光(guang)管(guan)(guan)損壞(huai)。萬用表選(xuan)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)R×10擋(dang)(dang)，紅(hong)、黑表筆(bi)(bi)分別接輸(shu)入、輸(shu)出端測發光(guang)管(guan)(guan)與受(shou)光(guang)管(guan)(guan)之間(jian)的(de)絕(jue)(jue)緣電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(有條件應用兆(zhao)歐表測其絕(jue)(jue)緣電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，此(ci)時(shi)兆(zhao)歐表輸(shu)出額定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)壓應略低(di)于被測光(guang)電(dian)(dian)(dian)(dian)(dian)(dian)耦合器所允許(xu)的(de)耐壓值)，發光(guang)管(guan)(guan)與受(shou)光(guang)管(guan)(guan)問絕(jue)(jue)緣電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)正(zheng)常(chang)(chang)應為(wei)∞。
14．光敏電阻的檢測
將萬(wan)用(yong)表撥到R×1kΩ擋，把(ba)光敏(min)電(dian)(dian)阻(zu)(zu)(zu)的受(shou)光面(mian)與(yu)入射光線保持垂直，于(yu)是在萬(wan)用(yong)表上直接測(ce)得的電(dian)(dian)阻(zu)(zu)(zu)就是亮阻(zu)(zu)(zu)。再把(ba)光敏(min)電(dian)(dian)阻(zu)(zu)(zu)置于(yu)完(wan)全黑(hei)暗(an)的場所，這時萬(wan)用(yong)表所測(ce)出的電(dian)(dian)阻(zu)(zu)(zu)就是暗(an)阻(zu)(zu)(zu)。如(ru)果亮阻(zu)(zu)(zu)為(wei)幾千歐(ou)至幾十干歐(ou)，暗(an)阻(zu)(zu)(zu)為(wei)幾至幾十兆(zhao)歐(ou)，說明光敏(min)電(dian)(dian)阻(zu)(zu)(zu)是好的。
15．激光(guang)二極管損壞(huai)判別
拆(chai)下(xia)(xia)激光(guang)(guang)二(er)(er)極管，測量其阻(zu)值(zhi)(zhi)，正(zheng)常情況下(xia)(xia)反(fan)向阻(zu)值(zhi)(zhi)應為(wei)無(wu)窮大，正(zheng)向阻(zu)值(zhi)(zhi)在20kΩ～40kΩ。如果所測的(de)正(zheng)向阻(zu)值(zhi)(zhi)已超(chao)(chao)過(guo)50kΩ，說明激光(guang)(guang)二(er)(er)極管性能(neng)已下(xia)(xia)降；如果其正(zheng)向阻(zu)值(zhi)(zhi)已超(chao)(chao)過(guo)90kΩ，說明該管已損壞，不(bu)能(neng)再使(shi)用了(le)。
