How to identify and detect common diodes?
How to identify and detect common diodes?
polarity identification
Intuitive judgment. Some of the circuit symbols are printed on the diode to indicate polarity; one end of the negative pole of the diode is printed with a color ring as a negative mark; some of the two ends of the diode shape is different, the flat head is the positive pole, the round head is the negative pole. Attention should be paid to the use of identification, with symbols on the basis of symbol recognition. For example, a diode can be used to identify and detect pins with a multimeter. Put the multimeter in RX1K2 block, two stylus respectively receive the two ends of the diode, if the measured resistance value is small, then the forward resistance of the diode, at this time with the black pen ( that is, the battery cathode in the table ) is connected to the diode positive, and the red pen ( that is, the battery anode in the table ) is connected to the diode cathode. 2 Good or bad judgment. If the measured resistance is very large, it is the reverse resistance of the diode. At this time, the diode negative pole is connected with the black pen, and the positive pole of the diode is connected with the red pen . The forward and reverse resistance of the diode should be very different, and the reverse resistance is close to infinity. If the positive and negative resistance of a diode are infinite, it is explained that the internal circuit of the diode is damaged; if the positive and reverse resistors are zero, the diode has been short-circuited by breakdown; if the difference between the positive and negative resistance is not big, it shows that the quality of the diode is too poor to be used.
The silicon and germanium tube can be distinguished by measuring the forward resistance of the diode, because the pressure drop of the forward tube of the germanium diode and the silicon diode is different. If the forward resistance is less than 1 k0, the germanium diode. If the forward resistance is 1 to 5 k2, then it is a silicon diode. When measuring with diode block of digital multimeter, the forward voltage value can be directly displayed. 0.2 ~ 0.3 V for the germanium tube, 0.6 ~ 0.7 V for the silicon tube.
Reverse voltage measurement General low voltage circuit diode can not measure voltage,for example,a high voltage power supply can be measured to be connected with the circuit shown in Figure. Adjust the Ec value, when the ammeter needle swing, the voltmeter ( V ) indicates that the diode reverse voltage.