How to use a pointer multimeter to determine the polarity of a transistor
① To distinguish the base b, set the pointer multimeter to the 1K position, connect the black probe to any pin of the transistor, and the red probe to the other two pins to measure the forward and reverse resistance values of the transistor until both measured resistance values are high (if one resistance value is high and the other is low during measurement, the black probe needs to be switched to another electrode before measurement). At this point, the electrode connected to the black probe is the base b of the transistor. And the tested transistor is a PNP transistor. If the resistance values of the two electrodes being measured are both very small at this time, then the base b of the transistor connected to the black probe is an NPN transistor, and the transistor being measured is an NPN transistor.
② Discrimination between collector c and emitter e; For germanium material PNP and NPN transistor, the above method can be used to first determine the base b of the transistor, then place the pointer multimeter in the R * 1K position, measure the resistance values of the remaining two electrodes, and swap the two probes. In the measurement with a smaller resistance value, if the tested transistor is PNP type, the electrode connected to the red probe is collector c, and the electrode connected to the black probe is emitter e. If the tested transistor is an NPN transistor, the electrode connected to the red probe is the emitter e, and the electrode connected to the black probe is the collector c.
For NPN type silicon material transistor, a 100K Ω resistor can be connected between the base b and the collector c. According to the above measurement method, the resistance value between the two electrodes except for the base b can be measured. The smaller resistance value is measured with the black probe connected to the collector c of the transistor and the red probe connected to the emitter e.
Knowing the three poles of a transistor, there is a convenient way to preliminarily estimate its amplification capability.
For NPN type transistor made of silicon material; Set the multimeter to the Rx1K position, with the red probe connected to collector c and the black probe connected to emitter e. If the base is empty, hold the collector c of the transistor with one hand. The human body is like a base bias resistor, and use your tongue to lick the base of the transistor. At this point, the pointer of the pointer type multimeter will immediately change from a high resistance value to a low resistance value (i.e., swing resistance value). This method may be a bit outdated, but it is very suitable. Interested friends can give it a try.
