How to determine which pin is the base using a multimeter
The first step of testing is to determine which pin is the base. At this point, we take two electrodes (such as electrodes 1 and 2) and measure their forward and reverse resistance by reversing the two probes of a multimeter. We observe the deflection angle of the probe; Next, take electrodes 1 and 3, as well as electrodes 2 and 3, and measure their forward and reverse resistance by reversing them respectively. Observe the deflection angle of the pointer. In these three inverted measurements, there must be two measurement results that are similar: that is, in the inverted measurement, the pointer deviates greatly in one measurement and slightly in the other; The remaining measurement must be reversed, and the deflection angle of the pointer before and after the measurement is very small. The foot that was not measured this time is the base (b) we are looking for.
2, After identifying the base of the transistor, we can determine the conductivity type of the transistor based on the direction of the PN junction between the base and the other two electrodes. Connect the black probe of the multimeter to the base and the red probe to either of the other two electrodes. If the pointer of the multimeter head deviates greatly, it indicates that the tested transistor is an NPN transistor; If the deflection angle of the meter pointer is very small, the tested tube is PNP type.
3, Determine collector and emitter: (1) For NPN transistors, measure the positive and negative resistance between the two poles by reversing the black and red probes of a multimeter. Although the deflection angle of the multimeter pointer is small in both measurements, careful observation shows that there will always be one deflection angle that is slightly larger. At this time, the black probe must be connected to the collector (c) and the red probe must be connected to the emitter (e).
(2) For PNP type transistors, measure the forward and reverse resistance between the two poles by reversing the black and red probes of a multimeter. When the pointer deviates slightly, the black probe must be connected to the emitter (e) and the red probe must be connected to the collector (c)
