Digital Multimeter Diode On Voltage Detection
In this gear, the red pen is connected to the internal positive power supply of the multimeter, and the black pen is connected to the internal negative power supply of the multimeter. The connection between the two pens and the diode is shown in Figure 1.
(a) connection measurement, the measured diode positive conduction, the multimeter shows the diode's positive conduction voltage, the unit is mV. usually good silicon diode positive conduction voltage should be 500mV ~ 800mV, good germanium diode positive conduction voltage should be 200mV ~ 300mV. if the display is "000", then the diode breakdown short circuit. If "000" is displayed, it means that the diode is short-circuited, if "1" is displayed, it means that the diode is not available in the forward direction.
(b) connection measurement, should show "1", that the diode reverse cut-off, if the display "000" or other values, it means that the diode has been reverse breakdown. This file can also be used to determine the good and bad triode and pin identification. Measurement, the first pen connected to a identified pin, another pen is successively connected to the remaining two pins, if so measured twice are on or are not on, and then replace the two pens and then measured, both are not on or are on, it can be determined that the transistor is good, and can be determined that the identified pin is the base of the transistor. If the red pen is connected to the base, the black pen were connected to the other two poles are on, then the transistor is NPN-type, and vice versa, is PNP-type. Finally, compare the size of the two PN junction positive conduction voltage, the reading is larger be junction, the reading is smaller bc junction, thus the collector and emitter are identified.
