TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
13
GROUND CANCELLATION (continued)
MANUAL GROUND CANCELLATION
In most situations, it is preferable to push the trigger switch to activate FASTGRAB™
automatic ground cancellation. Generally, it is best to first let the computer automatically
cancel interference from ground minerals. However, for gold prospecting, searching on a wet
saltwater beach, or searching in an area with so much metal trash that there is no
clean
ground for the computer to sample, we recommend that you cancel ground manually. Manual
ground cancellation requires a bit of skill, acquired with some practice.
The range of ground cancellation settings indicated on the display range from 0 to 99;
however, each displayed number spans 5 detent steps on the settings knob. The actual
internal ground cancellation setting changes with each step; there are a total of 500 different
settings. Under some ground conditions you may be able to hear the individual steps in the
setting.
The Fe
3
O
4
bar graph on the LCD display indicates the
amount
of magnetic mineralization.
The searchcoil must be in motion to measure Fe
3
O
4
. The most accurate measurement is
obtained by
pumping
the searchcoil, as in the Ground Cancellation procedure.
The two-digit G.C. Phase number displayed on the LCD indicates the
type
of ground
mineralization.
Some typical ground mineralization types are:
0 – 10 Wet salt and alkali
5 – 25 Metallic iron (very few soils in this range. You may be balancing over metal)
26 – 39 Very few soils in this range — occasionally some saltwater beaches
40 – 75 Red, yellow, and brown iron-bearing clay minerals
75 – 95 Magnetite and other black iron minerals
When manually ground canceling, try to “feel out” a spot on the ground to make sure there is
no metal present.
In order to avoid locking onto metal, the computer will not cancel ground
where the numbers are less than 40. Where the ground reads less than 40, manual ground
cancellation is required.