All users of metal detectors want to get an advantage over their device. One of the ways to get more extra out of your machine is to get a detector coil specific to the situation.
When you have the right metal detector coil for the right job detection will become easy and accurate. You wouldn’t want to use mud/sludge rims or tires on the road. The same applies to metal detectors. Now, which coil is right for me? Smaller coils tend to be more sensitive and get better separation. Larger coils get a better depth but can mask targets nearby. Every metal detection situation is different and certain coils have advantages in different locations.
Most of the time the common coil will give you the best results for that specific metal detector. Metal detector manufacturers spend many hours making the best detector coil of all. At this moment the two main coils are the DD coil and the concentric coil or also called mono loop. The concentric coil detects in snow cone shape, the shape of the DD coil is more like an I shape. The DD coil separates much better and obtains a more uniform depth, especially in mineralized soil.
The concentric coil consists of a TX coil and a RX coil, which are usually circular and arranged. The advantage of this coil is that both TX and RX coils are as large as possible in the diameter of the coil. This provides the largest possible field and depth of detection, making it the most sensitive coil available.
In addition, the concentric coils provide the most symmetrical detection field, which allows easier location and consistency in the identification of objects. For these reasons, they are the most commonly used coils with the best performance in all environments.
Unfortunately, this configuration is the most susceptible to interference from soil mineralization, resulting in substantial yield loss when used in soils with high mineralization.
The bobbin Double-D (or DD) is designed to significantly reduce soil interference, thereby restoring the yield lost by the concentric coil in the mineralized soil. With the Double-D coil, it is the arrangement of the TX and RX coils that produce a cancellation effect on the ground signals.
This coil is called Double-D or DD because both TX and RX coils are in the form of a “D”. The positive detection field of the DD coil runs below the central overlapping section from front to back. The remaining portion of the coil produces a negative detection field. It is this negative or cancellation field that allows the DD coil to maintain performance on mineralized soil.
Due to its small positive detection field, the DD coil is less sensitive than a concentric coil of the same size on non-mineralized ground. The Double-D coil, however, significantly outperforms the concentric coil on mineralized soil. For this reason, it is highly recommended when detected on soil.