TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
31
SEARCH TECHNIQUES (continued)
Tips on Ground Canceling
When the
T
2+
first turns on, the ground cancellation Phase Number is preset to 90. This will
give a positive response on nearly all soils. If you search in the Discrimination Mode, you will
probably not have to cancel the ground. If you switch to All Metal Mode, ground cancellation
will probably be necessary.
You must find a spot of ground which is free of metal to accurately cancel the ground signal.
Before you attempt to Ground Cancel, sweep back and forth to see if any metal target is
present. Locate what seems to be a clear area and then Ground Cancel. Ground
Cancellation may be done automatically by pushing the trigger, or manually if you are in All
Metal Mode. After you have ground cancelled, sweep back and forth to see if there is little or
no audible response to the soil. This is best done either in All Metal Mode, or in Discrimination
Mode with discrimination set to zero. Alternatively, use the PinPoint trigger to check the spot.
If there is little or no response, ground cancellation was successful. If there is still substantial
response, there may have been metal present where you attempted to ground cancel, so find
another promising spot and try again. If you cannot find a spot to successfully ground cancel,
it is time to give up. Turn the machine off, turn it on again so the ground balance preset will be
restored, and then use the machine without ground canceling.
In most areas, once you have ground cancelled, the ground cancellation setting will remain
satisfactory for a long time. However, if the soil has been disturbed by digging or the addition
of fill dirt, or if you are in a geologically complex setting such as is commonly encountered in
gold prospecting areas, you may have to frequently perform the ground cancellation procedure
to accommodate changing soil conditions.
When you ground cancel, the numerical Ground Phase Setting will momentarily appear on the
LCD screen. In general, sandy or gravelly soils will tend to read in the 75-95 range, light
colored loams and clays will tend to read in the 50-80 range, and red clays will tend to read in
the 35-55 range. To express it in other terms, the more highly weathered and oxidized the soil
is, the lower the numeric reading will be.
The Fe3O4 bar graph indicates how much iron mineralization is present. For it to work, the
searchcoil must remain in motion. The most accurate readings will be achieved by
pumping
the coil as you do when ground canceling. The higher the mineralization, the greater the
necessity to ground cancel the detector for the best depth performance.
If you are searching for relics, you can make a map of the soil of the site. Make a grid of the
site. Then collect data. Ground Cancel to document mineral
type;
view mineral
amount
on the
Fe3O4 bar graph. Then plot the data on the site map and draw isolines. In this way you may
be able to locate areas which have been dug, backfilled, or subjected to fire. This information
in turn helps to reveal the history of the site.