How do I test a bidirectional thyristor with a multimeter?
With a multimeter R × 1 block to determine the bidirectional thyristor electrode method, but also to check the trigger ability.
(1) determine the T2 pole: bidirectional thyristor G pole and T1 pole close to the T2 pole farther away. Therefore, G-T1 between the positive and negative resistance are very small. In the R × 1 block to measure the resistance between any two legs, only in the G-T1 presents a low resistance between the positive and negative resistance of only a few tens of Ω, while the T2 - G, T2 - T1 between the positive and negative resistance are infinite. This indicates that, if measured and the other two legs of a pin are not, it must be T2 pole. In addition, the use of TO-220 package bidirectional thyristor, T2 pole is usually connected to the small heat sink, according to which can also determine the T2 pole.
(2) Distinguish between G pole and T1 pole.
(1) find out the T2 pole, first of all, assuming that the remaining two pins in one of the pins for the T1 pole, the other pin for the G pole.
Connect the black pen to the T1 pole and the red pen to the T2 pole, and the resistance will be infinite. Then use the tip of the red pen to T2 and G short-circuit to the G-pole plus a negative trigger signal, the resistance value should be about 10 Ω, proving that the tube has been on, the conduction direction of T1-T2. and then the tip of the red pen and the G-pole off (but still connected to the T2), if the resistance value remains unchanged, proving that the tube can be triggered to maintain the state of conduction after the trigger.
③ the red pen to the T1 pole, the black pen to the T2 pole, and then make T2 and G short-circuit, to the G pole with a positive trigger signal, the resistance value is still about 10 Ω, and the G pole after disconnecting if the resistance value remains unchanged, it is shown that the tube is triggered, in the T2 - T1 direction to maintain the state of on-state, therefore, has a bi-directional trigger nature. This proves that the above assumption is correct. Otherwise, the assumptions do not match the actual situation, so it is necessary to make assumptions again and repeat the above measurements. Obviously, in the process of identifying G and T1, the triggering capability of the bi-directional thyristor is also checked. If the measurement is not able to trigger the bi-directional thyristor according to any of the assumptions, it proves that the tube is damaged. For 1 A tube, can also use R × 10 block detection, for 3 A and more than 3 A tube, should choose R × 1 block, otherwise, it is difficult to maintain the conduction state.
