Metal Detectors: Are they all the same?

Here is some information about the main types of metal detecting technology.

1) TR (Transmitter/Receiver) is the earliest technology based on Induction Balance (IB) principle of metal detection. TR detectors are able to tell the difference between a ferrous and nonferrous object, but do not have enough depth in highly mineralized ground. TR detectors are obsolete now.

2) BFO (Beat Frequency Oscillation) is another old technology based on Induction Balance (IB) principle. BFO metal detectors are the cheapest (under $100) and designed mainly as toy detectors for kids. Because the BFO technology is the easiest and cheapest to make, it has its limitations when compared to other types. For example, poor ability in distinguishing between different types of metals is one of them. BFO technology is also still used in cheap hand-held devices.

3) VLF (Very Low Frequency) metal detectors are the most common detectors and great for their ability in distinguishing between different types of metals. VLF detectors in the 4 khz range are the best in working the ground with high mineral content, and very sensitive to silver and copper targets, however they are not sensitive to gold. Metal detectors that are specially designed for electronic gold prospecting have frequencies ranging from 18kHz to 71kHz.

4) VLF/TR technology represents a combination of Very Low Frequency and Transmitter/Receiver technologies thus enabling the VLF/TR detectors to control trash and ground mineralization simultaneously.

5) PI (Pulse Induction) metal detectors cannot discriminate between different types of metals - this makes their use on inland sites with high concentration of trash extremely difficult. PI detectors are the best to use in salt water or highly mineralized soils where other types have trouble working. Targets can be detected much deeper with PI technology than with other types.