Check the triac with a digital multimeter

The picture on the left is a schematic diagram of testing using a digital multimeter. Set it to the NPN position, first open the G pole of the bidirectional thyristor VT, pass the current limiting resistor R (about 330Ω) into the "C" hole of the hFE socket, and pass the T1 pole. Insert the wire into the "E" hole. The role of the resistor R here is to prevent the hFE line from being overloaded. At this time, the digital multimeter displays a value of "000", indicating that it is in the off state. Then use a wire to short-circuit the G pole and T2. The multimeter number immediately jumped from "578", which means it has been turned on. The picture on the right is a verification circuit for the two-way conduction of the bidirectional thyristor. The difference from the picture on the left is that T1T2 is exchanged, and the G pole is still connected to the C pole through the wire Touch it, and the digital multimeter display value changes from "000" to "428". This proves that the bidirectional thyristor can conduct in both directions and the quality is good.