Way thyristor SCR polarity determination is made of a semiconductor material constituting the three PN junctions, their basic structure, and the equivalent circuit symbols. SCR has three electrodes: the anode (A), cathode (K) and control electrode (G). From the equivalent circuit, between the anode (A) and the control electrode (G) are the two opposite polarity in series PN junction between the control electrode (G) and the cathode (K) is a PN junction. According to the one-way electrical properties of the PN junction, the pointer to select the appropriate multimeter resistance profile SCR T435-600T, test poles between positive and negative resistance (SCR same poles, will lead to exchange two resistance values ??measured) For positive and negative normal SCR, G, K a big difference between the resistance; G, K, respectively, and positive and negative A small difference between the resistance and the resistance are great. This test result is only, according to this uniqueness can determine the polarity of the thyristors. After distinguishing T1 G pole and pole (1) identify the T2 pole, first assume that the rest of the feet in a foot of Tl pole, the other foot for G pole. (2) the black pen then T1 extremely SCR BT137S-600E, the red pen then T2 pole SCR BT136S-600E, resistance is infinite. Followed by the red pen to T2 and G short for G-pole with a negative trigger signal, the resistance value should be around ten Euro (see Figure 4 (a)), the tube has proved conduction, conduction direction T1 a T2. Then the red and G electrode tip disengaged (but still connected to T2), if the resistance value remains unchanged, to prove the tube after the trigger can be maintained in the ON state. SCR, are fertile Electronics (certified), SCR provided by the Dongguan City is Wal-Electronic Technology Co., Ltd. Dongguan City is Wal-Electronic Technology Co., Ltd. (www.dgmydz.com) (www.dgmydz.com) is Dongguan, FET leader, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, the maximum limits to meet customer needs. Wal-electronics leader in the positive with the staff warmly welcome all inquiries negotiations to create a positive future Wal-electron better.