1, the characteristics of the diode
The English of the diode is diode. The diode is positive. Negative two terminals, (Figure 1), the positive terminal A is called the anode, and the negative terminal B is called the cathode. The current can only move from the anode to the cathode.
2. How to measure the positive and negative poles of a diode with a multimeter
When performing simple tests on the semiconductor diode government pole, the ohmmeter of the multimeter should be used. The measurement method is as shown in (Fig. 2, Fig. 3). The red test pen connected to the multimeter + input communicates with the negative pole of the power supply in the watch; the black test pen connected to the multimeter is connected to the positive pole of the power supply in the watch.
The method of measurement is to first dial the multimeter to the "ohm" file (usually R&TImes; 100 or R&TImes; 1K), and then use a multimeter to connect to the two poles of the diode. When the power supply in the meter causes the diode to be in the forward connection mode, the diode is turned on and the resistance is small (the range of tens of ohms to several thousand ohms), which tells us that the positive pole of the diode when the black meter pen contacts; the red meter pen contacts The negative pole of the diode (see Figure 3); when the power supply in the meter causes the diode to be in reverse connection, the diode is turned off and the resistance is very large (generally several hundred kilohms), which tells us that the black meter is in contact with It is the negative pole of the diode, and the red test lead is in contact with the positive pole of the diode.
3. Use the multimeter R&TImes; 100 files and R&TImes; 1K file to measure the forward resistance of the same diode, why the resistance is different.
When the forward resistance of the same diode is measured by the R×100 gear position and the R×1K gear position of the multimeter ohmic gear, the measured resistance values ​​are different. This is because the equivalent internal resistance r corresponding to the two ranges of R×100 and R×1K is different, and the current flowing through the meter is different when the power supply voltage E is constant.
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