ID and PID
Metal detectors use a numerical evaluation system called ID (Identification Number) or PID (Phase Induction Number), which is based on the conductivity and ferromagnetic properties of the detected object. This system allows the user to estimate what type of metal the detector has detected based on the number displayed.
Working principle:
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Conductivity of the object: metal detectors use the principle that different metals conduct electric current differently. When the detector receives a signal from an underground object, it measures its conductivity. The higher the conductivity, the higher the ID number.
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Signal phase: Some detectors also measure the phase of the electromagnetic signal, which can help distinguish metals by their magnetic properties (e.g. ferromagnetic iron vs. non-ferromagnetic metals such as gold or silver).
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Number range: The ID or PID number scale typically covers a range from very low values that correspond to ferrous objects, to higher values for non-ferrous metals such as copper, silver, gold, etc. Each detector manufacturer may have a slightly different numerical scale, but the basic principle remains the same.
ID variability:
It is important to remember that ID numbers can be affected by various factors such as the depth of the object, soil mineralization, size and shape of the object, or the presence of other nearby metals. Therefore, it may be useful to rely not only on the number displayed, but also on the detector's audio signal and the user's experience.
Discrimination settings:
Depending on the numerical ID, users can set the detector to ignore certain ranges (e.g., iron), which helps reduce unwanted signals from debris such as nails or cans.
This ID system makes it much easier to decide which signals are worth digging up, and which can be safely ignored.