Minelab F3 Mine Detector Operation Manual page 33

Movement of the coil during the entire Ground Balance procedure
should be slow, continuous and smooth and each down and up
movement should take 3 to 4 seconds.
If the Ground
30 seconds of starting the procedure, release the Ground Balance
button and repeat this procedure.
If there is metal in the ground under the coil whilst Ground
Balancing, the detector will not Ground Balance correctly. Move the
detector and repeat the Ground Balance over ground that is free of
any metallic objects.
After the Ground Balance procedure is completed the detector will
automatically cancel interference from the ground under the coil. If
ground conditions change (changing mineralisation in the ground)
this procedure may need to be repeated.
c. STEP 3
 Ensure the operator‟s hands and arms are free of metallic objects
(watches, rings etc), and that no other metallic objects are near
the coil. The orientation of the Test Piece during the test is
dependent on which Sensitivity Endcap is connected to the
detector.
Figure 19: Ground Balance Procedure
Balance
Test Piece
NOTE
OK tone is
30
not heard within