Comprehensive Operating Manual & Guide to Metal Detecting
Comprehensive Operating Manual & Guide to Metal Detecting
26
23
F75
LIMITED
F75
LIMITED
Discrimination Mode (continued)
CL: CACHE LOCATING PROCESS
This process is an enhanced sensitivity, slow-speed, version of the dE (default) process.
Its primary use is in locating large deep objects while sweeping the searchcoil several
inches above the surface of the ground; under these conditions it goes deeper than the
other processes. When the cache locating process is selected, the response
characteristics of the Motion All Metal Mode are also modified; these characteristics
include less noise and a slower response speed. In many situations, you may prefer to do
cache locating in the Motion All Metal Mode after first selecting the Cache Locating
process in the Discrimination Mode.
WHAT YOU SEE VS. WHAT YOU HEAR
The visual target ID displayed on the LCD is based entirely on sampled processing; the
number displayed represents a snapshot of the target’s identification as the searchcoil passes
over the object. When using these different processes, or methods, the detector’s audible
response may differ from the visual. When using the different processes, there is not a 100%
correspondence between what you see and what you hear, especially on buried targets where
ground minerals influence target ID and audible response. By making the audio and visual
systems independent, the F75 allows each system to do what it does best. The audio is
optimized for quick response and target feel, whereas the visual system provides the best
numeric resolution of target ID.
LCD Visual Display (continued)
Since different metal objects can produce similar signals, and since minerals in the soil can
distort the signals, the probable target ID's are just that -- probable. There is no way of
knowing for sure what's buried other than to dig it up. Experienced metal detector users have
a rule of thumb -- "when in doubt, dig".
DEPTH
When the trigger is pulled to facilitate pinpointing an object, the 2-digit numerical display
indicates the approximate depth of the object, in inches, based on the assumption that the
object is a typical U.S. coin. Small objects will read deeper than they actually are, and large
objects will usually read shallower than they actually are.
The DEPTH bar graph on the left of the display divides target depth into shallow, medium, and
deep. This depth range appears while searching, and is less accurate than the value derived
using the pinpoint toggle switch.
Bar graph ranges for a coin-sized object are Shallow (0-4inches), Medium (4-8inches), and
Deep (8).
CONF (Target Confidence Indicator)
This 6-segment graphic indicates how confident the detector is of the 2-digit target
identification it has assigned. If all 6 segments are displayed, you can be confident that the
target ID is accurate. If 3 or fewer segments are displayed, the confidence is very low.
Junk targets tend to produce lower confidence indications than coin targets of similar electrical
conductivity. Sloppy sweep technique also reduces the confidence indication. You can use
this indicator to train yourself to sweep more skillfully.
Fe
3
O
4
BAR GRAPH (magnetite)
This bar graph displays the magnetic mineralization factor, or magnetic susceptibility, of the soil.
Magnetic susceptibility is expressed in terms of the percent volume of the iron mineral magnetite,
which most black sand is made of. The depth to which objects can be accurately identified is
strongly influenced by the magnetic susceptibility of the soil. High Fe
3
O
4
values have a greater
effect on detection depth in the Discrimination mode than in the All Metal mode. For the most
accurate Fe
3
O
4
reading, pump the searchcoil as though you were ground balancing.
Fe
3
O
4
approx.
Range micro-cgs Description
3 7,500 uncommon but not rare, heavy mineralization
1 2,500 heavy mineralization, not uncommon in goldfields
0.3 750 heavy mineralization, but not uncommon in some regions
0.1 250 medium mineralization, typical
0.03 75 light mineralization, but common
0.01 25 light mineralization, your G. B setting may also be low
blank <14 quartz & coral white beach sands
F75ltdBLK-MANUAL.qx6 12/22/11 4:15 PM Page 23
