How to measure unidirectional thyristor with digital multimeter

Using the diode range of a digital multimeter to measure
　　the performance of unidirectional thyristors (SCRs) Unidirectional thyristors are referred to
　　as thyristors (SCRs), formerly known as thyristors. They are a type of controllable rectifier element. The circuit symbol is shown in Figure 1. A is the anode, K is the cathode, and G is the control electrode.
　　Unidirectional thyristor performance identification
　　Unidirectional thyristors are referred to as thyristors (SCRs), formerly known as thyristors. They are a type of controllable rectifier element. The circuit symbol is shown in Figure 1. A is the anode, K is the cathode, and G is the control electrode.
　　(1) To distinguish the electrodes, use the red test rod to contact any electrode without changing, and the black test rod to contact the other two electrodes respectively. If it displays 0.2 to 0.8V when it contacts one electrode, and overflows when it contacts the other electrode, the red test rod is connected to G, and the black test rod is connected to A when it overflows, and the other electrode is K. If the result is not as above, change the electrode of the red test rod and repeat the above steps until the correct result is obtained.
　　(2) Determine the trigger characteristics. The test current that the diode block of a digital multimeter can provide is only about 1mA, so it can only be used to examine the triggering ability of a low-power unidirectional thyristor. The operation method is as follows: Use the red test rod to keep in contact with A and the black test rod to touch K. At this time, overflow should be displayed (off state). Then, the red test rod should touch G while maintaining connection with A. At this time, the displayed value is generally below 0.8V (turned to the on state). Then, the red test rod is separated from the control electrode, and the on state will continue to be maintained. If this is the case after repeated tests, it means that the tube is sensitive and reliable in triggering. This method is only suitable for tubes with small maintenance current.