{"id":15652,"date":"2026-01-06T17:48:34","date_gmt":"2026-01-06T09:48:34","guid":{"rendered":"http:\/\/www.erun-tech.com\/?post_type=dt_portfolio&p=15652"},"modified":"2026-01-06T17:48:34","modified_gmt":"2026-01-06T09:48:34","slug":"diangongjichushicaoerjiguandeshibieyuceliang","status":"publish","type":"dt_portfolio","link":"http:\/\/www.erun-tech.com\/en\/project\/diangongjichushicaoerjiguandeshibieyuceliang","title":{"rendered":"Basic electrician practice: identification and measurement of diodes"},"content":{"rendered":"
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Basic electrician practice: identification and measurement of diodes<\/h1>\n
Fundamental Skills Training in Marine Electronics and Electrical Systems<\/div>\n<\/div>\n
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I. Basic concepts of diodes<\/h2>\n
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A crystal diode is a semiconductor formed by a P-type semiconductor and an N-type semiconductor. PN junction<\/strong>The PN junction has a self-constructed electric field and a space charge layer on both sides of the interface. When there is no applied voltage, the diffusion current caused by the carrier concentration difference between the two sides of the PN junction and the drift current caused by the self-constructed electric field are equal and in an electrically balanced state.<\/p>\n

\n\n\n\n\n\n\n
Name<\/th>\ncircuit symbol<\/th>\nNote<\/th>\n<\/tr>\n<\/thead>\n
ordinary diode<\/td>\n\"\u7535\u5de5\u57fa\u7840\u5b9e\u64cd\uff1a\u4e8c\u6781\u7ba1\u7684\u8bc6\u522b\u4e0e\u6d4b\u91cf\u63d2\u56fe\"<\/td>\nunidirectional conductivity<\/td>\n<\/tr>\n
voltage regulator diode<\/td>\n\"\u7535\u5de5\u57fa\u7840\u5b9e\u64cd\uff1a\u4e8c\u6781\u7ba1\u7684\u8bc6\u522b\u4e0e\u6d4b\u91cf\u63d2\u56fe1\"<\/td>\nReverse breakdown regulator<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\"\u886812-

Table 12-1 Diode Symbols<\/p><\/div>\n

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II. Measurement of diodes<\/h2>\n
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1. Use a multimeter to determine the polarity of the diode<\/h3>\n
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(1) Pointer multimeter judgment<\/strong><\/p>\n

\u2460 Gear:<\/strong>Convert to resistive R x 100<\/strong> \u6216 R\u00d71k<\/strong>\u3002<\/p>\n

\u2461 Judgment:<\/strong>The meter pen makes steady contact with the pins. If the pointer is deflected (on), theblack pen<\/strong>The mating end isPositive (P)<\/strong>\uff0cred pen<\/strong>The mating end isNegative (N)<\/strong>\u3002<\/p>\n

\"c7975ff4fad779966b6e0b9d5879d72e-1\"<\/p>\n

Figure 12-6 Diode Measurement Schematic<\/p>\n<\/div>\n<\/div>\n

(2) Digital multimeter judgment<\/strong><\/p>\n

\u2460 Gear:<\/strong>switch toDiode special block<\/strong>. Shorting the meter pen should light up and beep.<\/p>\n

\u2461 Judgment:<\/strong>If the display digit changes (conducts), thered pen<\/strong>The mating end isanodal<\/strong>\uff0cblack pen<\/strong>The mating end iscathode<\/strong>\u3002<\/p>\n

Note:<\/strong>The red\/black pens of the digital and pointer meters have reversed internal battery polarity.<\/div>\n<\/div>\n<\/div>\n

2. Use a multimeter to determine the performance of the diode<\/h3>\n
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Core principles:<\/strong>Based on the unidirectional conductivity of the diode, the diode'sThe greater the difference between forward and reverse resistance, the better the performance<\/strong>\u3002<\/p>\n

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  • \u2705 Good performance:<\/strong>The forward resistance is small and the reverse resistance is large.<\/li>\n
  • \u274c Internal open circuit:<\/strong>Both the forward and reverse resistances are large (infinity).<\/li>\n
  • \u274c Internal short circuit (breakdown):<\/strong>The forward and reverse resistances are small.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<\/section>\n
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    C. Precautions for Diode Measurement<\/h2>\n
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    (1) Gear selection:<\/strong>Generally, use the R\u00d7100 block or R\u00d71k block. Do not use the R\u00d71 block (too much current is easy to burn out) or the R\u00d710k block (too much voltage is easy to break down).<\/p>\n

    (2) Deep analysis of detection principles:<\/strong>The positive terminal of the internal power supply of the multimeter is connected to the \u201c-\u201d Jack.<\/strong> is connected, and the negative terminal is connected to the \u201c+\u201d jack<\/strong> Connect (for pointer meter). Therefore, the positive connection is made with the black pen connected to the positive terminal.<\/p>\n

    (3) Determination of results:<\/strong>If there is not much difference between the two resistance values, it means that the performance is not good enough to be used.<\/p>\n

    It is important to note:<\/strong>The diode volt-ampere characteristic is non-linear. The resistance will vary when measured with different resistance blocks; in practice, the diode presents a smaller resistance value for higher currents in operation.<\/div>\n<\/div>\n<\/div>\n<\/section>\n