Minelab SD2200V2 Instruction Manual page 21

Instruction Manual Page 9
If a target signal is too weak for the detector to discriminate when it is set
in one of the discriminating modes, it will revert to the All Metal mode. As
soon as the signals become strong enough, the detector will resume
discrimination.
It is not advisable to pinpoint in the Disc + ID mode because the duration of
the signal is too long (too "broad" a signal). Pinpointing is best performed
in the All Metal mode.
It is recommended that once a target has been located and the operator is
using the discriminator, the coil should be rapidly passed back and forth
over the target centre several times. Remember to switch back to Fixed
balance for this.
The coil must at all times, particularly when discriminating or ID'ing a target,
be passed smoothly over the surface of the ground while maintaining the
coil height above the ground.
The form of ferrous discrimination which blanks the signal will not work if a
monoloop coil is used instead of the recommended Double 'D'. In that
case the Disc mode will be identical in response to the All Metal mode.
The Disc + ID mode will operate in the +ID mode giving pitch discrimination,
but will still not blank ferrous signals.
The operation of the Disc + ID mode is affected by signals which are too
strong. If the signal is too strong in +ID mode, the detector will emit a
rapidly pulsing signal of constant pitch. This is to guard against erroneous
interpretation indicating an overload of signal. Lift the coil slightly higher
above the ground and the discrimination functions will return.
The Disc mode discrimination will only blank a ferrous signal when a target
gives a strong signal when passing across a piece of iron, a target response
will be heard until the SD2200v2 identifies that the target is indeed iron. At
this point, the signal will "blank". The target strength required for this to
occur can be adjusted using the Discrimination Level Adjust Control.
Figure 7 - Discrimination Audio Signal