How does the polarity of the transistor judge?

   (NPN) or common N (PNP) poles of the equivalent diode of the transistor, and then use the multimeter to measure the inter-pole resistance (NPN), and then use the multimeter to measure the resistance of the diode (NPN) PNP is measured between the P pole resistance. Will be painted with a finger saliva, uh is the saliva, the total P pole and one of the N pole on the wet finger, and then measure the resistance between the two N pole, be sure to use a positive pole pen on the wet finger on the N pole , To see whether the resistance becomes smaller, smaller that the N pole is the collector, a total of P for the control pole, the rest is the emitter. If the measured resistance is not a big change, the transistor anti-direction and then the test is certainly it. If it is a PNP tube, you need to place the negative pen on one end of the wet finger.

 

General pointer multimeter black pen is positive, red pen is negative, the digital table is roughly the same.
Wet finger role is between the N pole and P pole to form a resistance, multimeter is to provide power to the transistor to work, the work of the transistor BE pole due to the transistor's amplification becomes smaller, so to determine the transistor's pole Sex.