■ F type probe: measure the thickness of non-magnetic coatings (zinc, copper, enamel, plastic and so on) on magnetic subtracts (iron, steel) N type probe: measure the thickness of non-conductive coatings (varnish ,enamel, plastic and so on) on conductive subtracts (zinc, copper, aluminum) ■ V-type probe to measure the cylinder easier ■ Single and continuous working mode ■ Low and high limits setting with judgement ■ With average calculation function