Any type of magnetic detector or magnetic metal detector such as pulse metal detector or VLF metal detector or TR metal detector because it uses magnetism if it wants to separate and discriminate metals with the VDI number it has the ability to separate and discriminate accurately and the magnetic system does not have stability in separation and discrimination because any type of magnetic detector or magnetic detector or magnetic metal detector such as pulse metal detector or VLF metal detector or TR metal detector can distinguish the difference between ferrous and non ferrous metal and this is also one of the factors In magnetic systems only the difference between metals is detected and there is no accurate separation and discrimination in any type of magnetic detector and in principle magnetism does not have stability in separation and discrimination