How to use a multimeter to measure the three poles of a bidirectional thyristor

In addition to one electrode G still called the control electrode, the other two electrodes of the bidirectional thyristor are usually no longer called the anode and cathode, but are collectively called the main electrodes T1 and T2. The bidirectional thyristor is a semiconductor with a 5-layer structure of NPNPN type. Its symbol and internal structure are shown in the figure below.

The method of using a multimeter to distinguish the electrodes of a bidirectional thyristor is: first find the main electrode T2. Set the multimeter to R×100, connect the black test lead to any electrode of the bidirectional thyristor, and the red test lead to the other two electrodes of the bidirectional thyristor. If the needle does not move, it means that the black test lead is connected to the main electrode T2. Otherwise, the black test lead should be replaced with another electrode, and the measurement should be carried out according to the above method until the main electrode T2 is found.

After T2 is determined, find T1 and G poles according to the following method. It can be seen from the figure that T1 and G are two PN junctions connected in reverse parallel. Due to design requirements and structural reasons, the resistance value between T1 and G still has a difference in the forward and reverse directions. Use the multimeter R×10 or R×1 range to measure the forward and reverse resistance between T1 and G. If one is about 22Ω and the other is about 24Ω, then the black test lead is connected to the main electrode T1 in the smaller resistance (forward resistance), and the red test lead is connected to the control electrode G.