There are different kinds of metal detectors, although they all seem to do the same thing. However, the difference is in the fact that they do it differently, each of these categories having its own characteristics. You have VLF, BFO and PI ones and here are some considerations on the latter kind of such devices.

These metal detectors have a search grill with only one coil, which is also called single pulse technology, unlike the VLF detectors, which are based on double pulse technology. The search coil generates an electromagnetic field which transmits energy to the metal object identified, this one also generating such a field which completes the first one. This couple is analysed during the break between the impulses sent by the detector.

As far as the advantages of such devices are concerned, here are a few considerations. First of all, these detectors can detect objects which are situated even five metres underground. Also, it makes no difference if the soil contains a lot of minerals or not, which is a different principle than what happens in the case of the VLF ones. Also, they are very stable.

On the other hand, when it comes to the disadvantages of these detectors, they start with the fact that you consume a lot more energy. Also, they can only separate metals at a distance of about twenty or thirty centimetres and the only separation they can determine is that between metal and non-metal objects. Also, they can't detect very small objects, such as pins or rings and other such objects.

You should use this kind of devices when you are doing depth searches. You can find treasures, metal pots and other such objects with these devices and you can also use them for security and archaeological purposes.