Test SensitivityMetal detectors are usually tested indoors for sale. Too many metals in the surroundings will bring many disturbances. It is highly recommended to operate the detectors according to steps in “Quick Start” of the manual.a) Put the stick and search-coil in the right position so as to reduce the disturbance of metal stick. Please take off the watch and ring.b) Put the search-coil 8" above the table and stay away from the ground and wall.c) Adjust the sensitivity to the highest level. Set the detection way in ALL METAL.d) Be cautious of the electromagnetic interference.e) Flat a US 0.25 "quarter" coin and move it horizontally at a certain speed at the regulated height above the center of search-coil.f) Sensitivity indicator is defined in the air. Sensitivity will be lowered in the mineralization soil or conducting soil.*Two metal detectors will work properly when testing them simultaneously.