Digital multimeter diode conduction voltage detection
In this gear, the red probe is connected to the internal positive power supply of the multimeter, and the black probe is connected to the internal negative power supply of the multimeter. The connection between the two probes and the diode is shown in Figure 1. If measured according to the connection method in Figure 1 (a), the measured diode will conduct in the forward direction, and the multimeter will display the forward conducting voltage of the diode, in mV. A good silicon diode should have a forward conduction voltage of 500mV to 800mV, and a good germanium diode should have a forward conduction voltage of 200mV to 300mV. If "000" is displayed, it indicates that the diode has broken through and short circuited. If "1" is displayed, it indicates that the diode is not working in the forward direction. If measured according to the connection method in Figure 1 (b), "1" should be displayed, indicating that the diode is cut off in reverse. If "000" or other values are displayed, it indicates that the diode has been broken down in reverse. This file can also be used to determine the quality of the transistor and identify the pins. When measuring, first connect one probe to a designated pin, and then connect the other probe to the other two pins in sequence. If this measurement results in both conducting or not conducting, then switch the two probes and measure again. If neither conducting nor conducting, it can be determined that the transistor is good and that the designated pin is the base of the transistor. If the red probe is connected to the base and the black probe is connected to the other two poles and both are conducting, it indicates that the transistor is NPN type. Otherwise, it is PNP type* After comparing the positive conduction voltage of the two PN junctions, the one with a larger reading is the BE junction, and the one with a smaller reading is the BC junction. Therefore, both the collector and emitter are recognized.
