【正文】 發(fā)黑或燒焦，可斷定是其負荷過重，通過它的電流超過額定值很多倍所致；如果其表面無任何痕跡而開路，則表明流過的電流剛好等于或稍大于其額定熔斷值。 20% error. 如不相符，超出誤差范圍，則說明該電阻值變值了。 20 ％的誤差。s the middle of a period of more refined indexing and should therefore be directed to the pointer value is the middle position as far as possible fall into the scale, that is the start of full scale of 20% to 80% within the arc, to to make measurements more accurate. 根據(jù)電阻誤差等級不同。 Especially for beginners, proficiency in monly used ponents of the detection methods and experience is essential, the following pairs of electronic ponents monly used method of testing experience and are introduced for the right test. Ⅰ一、電阻器的檢測方法與經(jīng)驗：.resistors detection methods and experiences: 1  resistor testing.TA 將兩表筆 ( 不分正負 ) 分別與電阻的兩端引腳相接即可測出實際電阻值。The two tables T (regardless of positive or negative) between two ends of pinphase resistance can be measured by the actual resistance value. 為了提高測量精度，應(yīng)根據(jù)被測電阻標(biāo)稱值的大小來選擇量程。According to a different level of resistance errors. 讀數(shù)與標(biāo)稱阻值之間分別允許有177。 Readings and the difference between the nominal resistance value is allowed 177。If not match, exceed the error range, then change the value of the resistor 注意：測試時，特別是在測幾十 k Ω以上阻值的電阻時，手不要觸及表筆和電阻的導(dǎo)電部分；被檢測的電阻從電路中焊下來，至少要焊開一個頭，以免電路中的其他元件對測試產(chǎn)生影響，造成測量誤差；色環(huán)電阻的阻值雖然能以色環(huán)標(biāo)志來確定，但在使用時最好還是用萬用表測試一下其實Note: The test, especially in the test scores of more than k Ω resistor values, the hands do not touch the table and the resistance of the conductive part of the pen。 In the circuit, when the fuse resistor fuse open circuit, may make judgments based on experience: If it is found fusing resistor surface black or charred, it can be concluded its overloaded by more than its current rating due to many times。Check potentiometer, the first rotating rotary handle, turn handle to see if rotation is smooth, the switch is flexible, switch pass, off time Cameroon clatter sound is crisp, and listen to a potentiometer, and resistors within the contact points of friction sound, if imperfections sound, indicating poor quality. 用萬用表測試時，先根據(jù)被測電位器阻值的大小，選擇好萬用表的合適電阻擋位，然后可按下述方法進行檢測。s file with the multimeter test 1, 2 (or 2, 3) at both ends of the potentiometer counterclockwise rotation of the shaft according to nearly off position, then the smaller the resistance value better. 再順時針慢慢旋轉(zhuǎn)軸柄，電阻值應(yīng)逐漸增大，表頭中的指針應(yīng)平穩(wěn)移動。 2 Ω內(nèi)即為正常。 Resistance if it is the actual difference between the nominal resistance value is too large, its performance is illustrated in bad or damaged. B 加溫檢測；在常溫測試正常的基礎(chǔ)上，即可進行第二步測試 加溫檢測，將一熱源 ( 例如電烙鐵 ) 靠近 PTC 熱敏電阻對其加熱，同時用萬用表監(jiān)測其電阻值是否隨溫度的升高而增大，如是，說明熱敏電阻正常，若阻值無變化，說明其性能變劣，不能繼續(xù)使用。NTC thermistor with the multimeter measuring methods and measured the same way as ordinary fixed resistor that, according to the nominal resistance of NTC thermistor select the appropriate power block can be directly measured the actual value of Rt. 但因 NTC 熱敏電阻對溫度很敏感，故測試時應(yīng)注意以下幾點： A  Rt 是生產(chǎn)廠家在環(huán)境溫度為 25 ℃時所測得的，所以用萬用表測量 Rt 時，亦應(yīng)在環(huán)境溫度接近 25 ℃時進行，以保證測試的可信度。 Test, do not pinch fingers thermistor body, in order to prevent the body temperature of the test impact. (2) 、估測溫度系數(shù)α t(2), estimate the temperature coefficient αt 先在室溫 t1 下測得電阻值 Rt1 ，再用電烙鐵作熱源，靠近熱敏電阻 Rt ，測出電阻值 RT2 ，同時用溫度計測出此時熱敏電阻 RT 表面的平均溫度 t2 再進行計算。8. photosensitive resistance 用一黑紙片將光敏電阻的透光窗口遮住，此時萬用表的指針基本保持不動，阻值接近無 black pieces of paper with a translucent window, the photosensitive resistor cover, this time multimeter pointer remained motionless close to infinite resistance. 此值越大說明光敏電阻性能越好。 The smaller this value shows the better performance of lightsensitive resistors. 若此值很大甚至無窮大，表明光敏電阻內(nèi)部開路損壞，也不能再繼續(xù)使用。 Measurements, it can use multimeter R 10k block, using two tables T 2 respectively, the capacitance of arbitrary access pin, resistance should be infinite. 若測出阻值 ( 指針向右擺動 ) 為零，則說明電容漏電損壞或內(nèi)部擊穿。 Can choose 3DG6 silicon transistor models such as the position of posite pipe. 萬用表的紅和黑表筆分別與復(fù)合管的發(fā)射極 e 和集電極 c 相接。 It should be noted: In the test operations, especially in the measured capacitance of a smaller capacity, they must repeatedly exchange the measured capactance pin contacts A, B two points, in order to clearly see the multimeter pointer swing. C 對于 0  01 μ F 以上的固定電容，可用萬用表的 R10k 擋直接測試電容器有無充電過程以及有無內(nèi)部短路或漏電，并可根據(jù)指針向右擺動的幅度大小估計出電容器的容量。 At this point the resistance is positive electrolytic capacitor leakage resistance, this value is slightly larger than the reverse leakage resistance. 實際使用經(jīng)驗表明，電解電容的漏電阻一般應(yīng)在幾百 k Ω以上，否則，將不能正常工作。C for the positive and negative signs unknown electrolytic capacitors can be measured using the above method to determine leakage resistance. 即先任意測一下漏電阻，記住其大小，然后交換表筆再測出一個阻值。Hand gently rotating shaft, should feel very smooth and should not feel tight and sometimes lax, and even catching the phenomenon. 將載軸向前、后、上、下、左、右等各個方向推動時，轉(zhuǎn)軸不應(yīng)有松動的現(xiàn)象。 In the rotating shaft of the process, if the pointer is sometimes point to zero, indicating movement between the film and the stator shortcircuit point。 (3) 次級繞組與外殼之間的電阻值。(6) The resistance is less than infinite, but greater than zero: There is leakage faults. 3 電源變壓器的檢測3. power transformer testing A 通過觀察變壓器的外貌來檢查其是否有明顯異常By observing the appearance of the transformer to check there is an obvious anomaly. 如線圈引線是否斷裂，脫焊，絕緣材料是否有燒焦痕跡，鐵心緊固螺桿是否有松動，硅鋼片有無銹蝕，繞組線圈是否有外露等。 Otherwise, it shows bad transformer insulation. C 線圈通斷的檢測。 Power transformer primary and secondary pins pins are usually respectively from both sides of the leads, and marked with the 220V primary winding multiword, the subwindings are marked rated voltage value, such as 15V, 24V, 35V and so on. 再根據(jù)這些標(biāo)記進行識別。當(dāng)初級繞組的插頭插入 220V 交流市電時，萬用表所指示的便是空載電流值。 (b) 間接測量法。 F 空載電壓的檢測。 2 ％。采用串聯(lián)法使用電源變壓器時，參加串聯(lián)的各繞組的同名端必須正確連接，不能搞錯。通常，線圈內(nèi)部匝間短路點越多，短路電流就越大，而變壓器發(fā)熱就越嚴重。此時不用測量空載電流便可斷定變壓器有短路點存在。 5%, with a centertapped windings of the two sets of symmetrical voltage difference should be ≤ 177。將兩表筆(不分正負)分別與電阻的兩端引腳