up/down button, according to the number of carats displayed below the instrument adjustment, you do not need to set the exact number of carats.But remember, for diamonds ( 1.0 carats), please turn on 1 green light; For diamonds (0.5 carats), turn on 2 green lights. For small gems (such as cuts or cones), turn on 3-4 green lights. We have to choose the size before using the tester.Otherwise we may get the incorrect result.[Bare Hands Operation Touch Panel]: We have to touch the panel on the back when testing. Othersize we get a wrong result The high-frequency sound during metal testing is due to the test pen's operational principle, which relies on thermal conductivity to distinguish between diamonds and fake gemstones. Since metal possesses thermal conductivity similar to diamonds, it generates a high-frequency sound during testing. the Tester Pen is easy to operate. Just turn it on, lightly press the tip to the gemstone, and wait for the beep to know if it's real or fake.If it's Real .The professional Tester lighted up over 9 and emits audible sounds. No reaction means the stone is a fake crystal or simulant like cubic (). The mini LED foldable magnifying is equipped with 30X 60X lens, portable and reliable to see the item you want to know, no worry about missing the details of gems; And you can also share them with your family members or to enjoy much fun., Manufacturer: Akfldms