I found my post on Tom D's forum about using the '88' display as a ground mineralisation meter. Rather than link to it, I'll revise my thoughts here: Ground signal strength, or Fe3O4 strength, varies a huge amount depending on location. It can be 1000 times stronger in the red Tennessee dirt than it is in Florida's sandy ground, or on freshwater beaches. This range makes it harder to describe in an easily presented way. Fisher's F75 uses a 6-bar bargraph, scaled as: Bar's labelling : Fe3O