Notch Variable Control - Minelab Sovereign GT User Manual

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7. Discrimination Control – Continued
6.
The Sovereign GT uses the electrical conductivity of the object to determine the type of metal detected,
and based upon the Disc control setting, will either ignore or accept the object. The most effective way
to demonstrate this is to consider a number of objects, all of varying conductivity, placed in order of
conductivity on the ground. (see figure 12).
Figure 12 - Target conductivity
Turn the Disc control further clockwise and objects of greater conductivity will be ignored. If the Disc
control is set to ignore the pull-tab, this will mean that all objects having a similar or lower conductivity
than the pull-tab will be ignored, while objects of higher conductivity will still be accepted (see figure 13).
Figure 13- Discriminating targets based on conductivity
Figure 13 shows some common objects and where the Disc control would have to be set to ignore them.
As a general rule, the two objects treasure hunters most commonly wish to ignore are aluminium foil and
pull-tabs. As can be seen in Figure 13, both of these objects cover a significant range on the Disc
control. The conductivities of objects that the user wishes to accept or ignore often overlap, so - setting the
Disc control to ignore both foil and pull-tabs will also ignore a large amount of valuable non-ferrous objects
including some coins, rings, and other jewellery which have conductivity levels between these junk items.
Example: If hunting for thin rings of white gold, with the Disc
control set to position 4 (see figure 14), some types of aluminium
foil will also be detected. To avoid old pull tabs, but detect brass
buttons and copper coins, the Disc control would need be set
higher (approximately at number 13).
At this setting most fine white gold rings, foil, and some yellow
gold rings will also be ignored. With experience, setting the Disc
control to ignore most unwanted targets (in combination with the
Notch control) will become second nature and you will develop a
preferred setting for different sites.
Figure 14- Disc control
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7.

Notch Variable Control

7.
Located on the centre left of the control panel, the Notch control is used in combination with
the Disc control to discriminate against, or ignore, certain metal objects. As with the Disc
control, this is continuously variable and features numerous graduations as a guide to
setting the control.
The main difference between the Notch and Discrimination controls is that Discrimination
sets a continuous band of discrimination, whereas the Notch selects a short segment of discrimination which
can be moved up or down the scale of conductivity.
Note: The Notch control will only be active, if set to a higher or more clockwise level than the Disc control.
As the Notch control is turned further clockwise, objects with a conductivity, within the width of its band, will
be ignored. Turning the Notch control to ignore the pull-tab will mean that only non-ferrous objects having a
similar conductivity to the pull-tab will be ignored while all other non-ferrous objects of different conductivity
are still accepted.
Note, in Figure 15 the ferrous objects are being ignored due to the Disc. setting on zero.
Figure 15 - Ignoring targets using the Notch control
When using the Notch and Disc controls in combination, most unwanted objects can be successfully ignored
(see Figure 15). Turning the Notch control to ignore the pull-tab and the Disc control to ignore the aluminium
foil will set up the Sovereign GT to ignore most pull-tabs and aluminium foil while still detecting most valuable
non-ferrous objects (see figure 16).
Note: Different pull-tabs may require a slight movement of the Notch setting. Obviously, if the amount of
pull-tabs is not numerous, then you may decide to leave the notch at minimum, which removes the risk of
discriminating a valuable object.
Figure 16 - Ignoring targets using the Disc and Notch controls
TIP: It is very important that you recognize the conductivity level of common coins, jewellery and trash targets
so that you know what items will be accepted or rejected at various levels. We recommend that you read and
follow Chapter 9 - Practising the Controls to be familiar with common targets in your area.
NOTE: If operating with Threshold, the operator will hear that a target has been discriminated or notched out
by the threshold going null (silent) and can determine if it was discriminated or notched by the tone of the
returning threshold ie: if the threshold returns in a deep tone, the object was discriminated and if the
threshold returns in a higher pitch it was notched out.
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