High as possible, Definitely Not. Moving the sens. up wards from the factory setting is a mistake as the detector is calibrated for the coil. Not all coils are the exact same so you could really mess things up by turning up the Sens to much. Also by turning it up, the coil sees more minerals under the coil and it actually gets less depth at some locations. The way to get more depth is with a larger coil. The detector is susceptible to outside interference this way with to high a setting. But you can experiment and see what happens.