【正文】 r increase, and thus easy to observe. 應(yīng)注意的是：在測試操作時，特別是在測較小容量的電容時，要反復(fù)調(diào)換被測電容引腳接觸 A 、 B 兩點，才能明顯地看到萬用表指針的擺動。10pF capacitors due to the following fixedsize too small to measure with the multimeter, only a qualitative check whether there is leakage, the internal short circuit or breakdown phenomenon. 測量時，可選用萬用表 R10k 擋，用兩表筆分別任意接電容的兩個引腳，阻值應(yīng)為無窮大。If the measured resistance is very small, shows varistors have been damaged and can not be used. 8 光敏電阻的檢測。 Be careful not to make the heat source and the PTC thermistor by too close or direct contact thermal resistance, in order to prevent their Tanghuai. 6 負溫度系數(shù)熱敏電阻 (NTC) 的檢測6. negative temperature coefficient thermistor (NTC) detection. (1) 、測量標(biāo)稱電阻值 R(1), measured nominal resistance value Rt 用萬用表測量 NTC 熱敏電阻的方法與測量普通固定電阻的方法相同，即根據(jù) NTC 熱敏電阻的標(biāo)稱阻值選擇合適的電阻擋可直接測出 Rt 的實際值。 Such as the multimeter pointer in the handle potentiometer shaft rotation in the process of beating the phenomenon, indicating activities, contacts are being exposed failures. 5 正溫度系數(shù)熱敏電阻 (PTC) 的檢測5. positive temperature coefficient thermistor (PTC) detection. 檢測時，用萬用表 R1 擋，具體可分兩步操作： A 常溫檢測 ( 室內(nèi)溫度接近 25 ℃ ) ；將兩表筆接觸 PTC 熱敏電阻的兩引腳測出其實際阻值，并與標(biāo)稱阻值相對比，二者相差在177。 If the measured resistance is infinite, then the fuse resistor has failed open circuit, if the measured resistance and the,nominal value falls far short of that change resistance values, we should not be used. 在維修實踐中發(fā)現(xiàn)，也有少數(shù)熔斷電阻器在電路中被擊穿短路的現(xiàn)象，檢測時也應(yīng)予以注Maintenance practices found that a small number of fuseresistor in the circuit was shortcircuit breakdown phenomena, testing, also should be noted. 4 電位器的檢測4 .potentiometer detection. 檢查電位器時，首先要轉(zhuǎn)動旋柄，看看旋柄轉(zhuǎn)動是否平滑，開關(guān)是否靈活，開關(guān)通、斷時 喀噠 聲是否清脆，并聽一聽電位器內(nèi)部接觸點和電阻體摩擦的聲音，如有 沙沙 聲，說明質(zhì)量不好。 20% error. 如不相符，超出誤差范圍，則說明該電阻值變值了。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。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。 Readings and the difference between the nominal resistance value is allowed 177。 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。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。 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。 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。 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。 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。 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。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。 (3) 次級繞組與外殼之間的電阻值。 Otherwise, it shows bad transformer insulation. C 線圈通斷的檢測。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。 F 空載電壓的檢測。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。此時不用測量空載電流便可斷定變壓器有短路點存在。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。如不相符，超出誤差范圍，則說明該電阻值變值了。在維修實踐中發(fā)現(xiàn)，也有少數(shù)熔斷電阻器在電路中被擊穿短路的現(xiàn)象，檢測時也應(yīng)予以注意。當(dāng)軸柄旋至極端位置3時，阻值應(yīng)接近電位器的標(biāo)稱值。負溫度系數(shù)熱敏電阻(NTC)的檢測。用萬用表的R1k擋測量壓敏電阻兩引腳之間的正、反向絕緣電阻，均為無窮大，否則，說明漏電流大。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。兩只三極管的β值均為100以上，且穿透電流要小。將萬用表紅表筆接負極，黑表筆接正極，在剛接觸的瞬間，萬用表指針即向右偏轉(zhuǎn)較大偏度(對于同一電阻擋，容量越大，擺幅越大)，接著逐漸向左回轉(zhuǎn)，直到停在某一位置。可變電容器的檢測用手輕輕旋動轉(zhuǎn)軸，應(yīng)感覺十分平滑，不應(yīng)感覺有時松時緊甚至有卡滯現(xiàn)象。被測色碼電感器直流電阻值的大小與繞制電感器線圈所用的漆包線徑、繞制圈數(shù)有直接關(guān)系，只要能測出電阻值，則可認為被測色碼電感器是正常的。否則，說明變壓器絕緣性能不良。將次級所有繞組全部開路，把萬用表置于交流電流擋(500mA，串入初級繞組?？蛰d電壓的檢測。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。電源變壓器發(fā)生短路性故障后的主要癥狀是發(fā)熱嚴重和次級繞組輸出電壓失常。10％，低壓繞組≤177。此值不應(yīng)大于變壓器滿載電流的10％～20％。將萬用表置于R1擋，測試中，若某個繞組的電阻值為無窮大，則說明此繞組有斷路性故障。檢測絕緣性能將萬用表置于R10k擋，做如下幾種狀態(tài)測試：(1)初級繞組與次級繞組之間的電阻值；(2)初級繞組與外殼之間的電阻值；(3)次級繞組與外殼之間的電阻值。用一只手旋動轉(zhuǎn)軸，另一只手輕摸動片組的外緣，不應(yīng)感覺有任何松脫現(xiàn)象。實際使用經(jīng)驗表明，電解電容的漏電阻一般應(yīng)在幾百kΩ以上，否則，將不能正常工作。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。如果萬用表指針始終停在某一位置不隨紙片晃動而擺動，說明光敏電阻的光敏材料已經(jīng)損壞。光敏電阻的檢測。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：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。正溫度系數(shù)熱敏電阻(PTC)的檢測。檢查電位器時，首先要轉(zhuǎn)動旋柄，看看旋柄轉(zhuǎn)動是否平滑，開關(guān)是否靈活，開關(guān)通、斷時喀噠聲是否清脆，并聽一聽電位器內(nèi)部接觸點和電阻體摩擦的聲音，如有沙沙聲，說明質(zhì)量不好。水泥電阻的檢測。由于歐姆擋刻度的非線性關(guān)系，它的中間一段分度較為精細，因此應(yīng)使指針指示值盡可能落到刻度的中段位置，即全刻度起始的20％～80％弧度范圍內(nèi)，以使測量更準確。s law calculate the load current I empty, that is, I empty = U / R. F noload voltage detection. will be the primary power transformer 220V electricity access, use multimeter measuring AC voltage,then turn out the windingload voltage (U21 , U22, U23, U24) should meet the requirement values, allowable error range is typically as follows: highvoltage winding ≤ 177。 I. 電源變壓器短路性故障的綜合檢測判別。 10 ％，低壓繞組≤177。一般常見電子設(shè)備電源變壓器的正常空載電流應(yīng)在 100mA 左右。 Will be placed in R 1 block multimeter, test, if a winding resistance value infinite, then there are the winding circuit failu