Cause of nail falsing?

[Diga]

Hello.

What characteristic(s) of a nail can cause it to false? The head, the elongated shape, the pointed tip? How much of a factor is the nail's orientation in producing a false or not?

[Carl-NC]

I assume you mean false positive, where the nail gives a non-ferrous response. All iron targets have a magnetic response and an eddy response. The magnetic response is on the ferrous side and the eddy response is on the non-ferrous side. Most nails are dominated by the magnetic response so they ID as ferrous. A short nail with a large head (roofing nail) might have a dominant eddy response and show as non-ferrous. A nail that is laying flat and pointed perpendicular to the coil sweep is more likely to false non-ferrous, but when you do a 90° sweep you should then hear the tell-tale ferrous double-beep. A 90° bent nail can false even from different sweep directions. Also, catching a nail on the edge or outside the edge of the coil can give a non-ferrous response, but if you figure out its true location (AM mode) and then do cross sweeps it should be easy to figure out. My strategy is to always use AM mode to get the exact target location and then sweep from different directions.