Features: 1. Test to confirm that the board under test is turned off and the electrolytic capacitors on the motherboard are fully discharged. It is strictly forbidden to test when the motherboard is powered on. 2. Confirm the optocoupler PIN1 (the pin with a small dot on the test board also has a corresponding pin) 3. Connect the optocoupler test board to the USB power cord, and test the optocoupler with the test board probe contact point. If the light in the optocoupler test board keeps flashing, it means that the optocoupler is good (the light brightness may be different from the optocoupler). As long as it flashes, it means that the optocoupler is good) 4. Measure to that the optocoupler test board has good contact with the tested optocoupler If the indicator light is always on or off, remove the optocoupler from the circuit board and insert it into the optocoupler seat of the breadboard to reconfirm the test results Applicable to 4-pin optocouplers, other types of optocouplers are temporarily Specifications: Part name:Optocoupler Tester 4th generation is Type-C interface, there is an indicator light when plugged in, need to be plugged in to use. NOTE: USB power cord NOT included. Color: Green Material: PCB + electronic components The actual product may have color difference due to different lighting or display Package Contents: 3 x Optocoupler Tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.