DR.ÖTEK MT9s Manual De Instrucciones página 11

3. If the detector flashes green normally but the sensitivity is so low
that you cannot use it to detect target objects, it is possible that
there are large metal objects nearby and the automatic calibration
reduces the sensitivity. You can hold the search coil up in the air
and restart the unit.
4. When detecting on the beach or in red soil areas, the unit sends
signals all the time, due to the interference of conductive sea sand
and mineralized soil. You can hold the search coil near the ground,
and restart the unit. The detector will calibrate itself and properly
reduce the sensitivity.
5. For circumstances of no response on touching, you may move your
finger more slowly over touching areas because this product is
equipped with inductive switches.