Comprehensive Operating Manual & Guide to Metal Detecting
Comprehensive Operating Manual & Guide to Metal Detecting
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F75
LIMITED
F75
LIMITED
Controls
ON-OFF & VOLUME Knob (Under the elbow)
This knob turns the machine on or off, and controls speaker volume and headphone volume.
Knob position has no effect on detector’s sensitivity or susceptibility to noise from electrical
interference
On/Off &
Volume
Switch
Menu
Access
Toggle From
bP or CL Process
Settings
Knob
Dual-function
Trigger switch
DUAL FUNCTION
MENU BUTTON
Search Techniques (continued)
Tips on ground balancing
When the F75 first turns on, the ground balance setting 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 balance to the ground. If you switch to All Metal mode, ground balancing
will probably be necessary.
You must find a spot of ground which is free of metal to accurately balance to the ground.
Before you attempt to Ground Balance, sweep back and forth to see if any metal target is
present. Locate what seems to be a clear area and then Ground Balance. Ground Balancing
may be done automatically by pushing the trigger, or manually if you are in All Metal mode.
After you have ground balanced, 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 balancing was successful. If there is still substantial response,
there may have been metal present where you attempted to ground balance, so find another
promising spot and try again. If you cannot find a spot to successfully ground balance, it is
time to give up. Reset the ground setting to 90 and then use the machine without ground
balancing.
In most areas, once you have ground balanced, the ground balance 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 balancing procedure
to accommodate changing soil conditions.
When you ground balance, the numerical Ground 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, oxidized, or finely grained
the soil is, the lower the numeric reading will be.
The Fe
3
O
4
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 balancing. The higher the mineralization, the greater the
necessity to ground balance 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 Balance to document mineral type; view mineral amount on
the Fe
3
O
4
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.
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