AKA SOREX PRO Operating Manual page 27

(less than 5 cm). At the same time signal level on the display is pretty high more than 50.
Two low frequency short signals mean that there is a long ferromagnetic object
(i.e. nail) located along the scanning direction. If such object is located across the
scanning direction or perpendicular to searchcoil plane, then the device gives single low
frequency short tone.
It's important to mention that DD-searchcoil has a complicated interaction
pattern with metal objects in close zone (signal levels more than 80).
That is why try to choose scan gap (distance) to provide 20 - 50 of signal level while
identifying object type.
In other words, try to indentify objects beyond close range zone if conditions
allow you to do so.
The so-called hot rocks cause problems during search operations ,their VDI is
more than +84. To distinguish hot rocks and relatively large flat nonferrous objects (for
example, five kopeks of Catherine II) VDI within +78 ...+86, device has special high-tone
signal that differs from the usual signal tone for a nonferrous metal object. Hot rocks
signal can be excluded using discriminator and setting value of first border to +86.
However the most effective hot rock neutralizer is not a discrimination HRN (hot rocks
neutralization) algorithm. With discrimination exclusion of sound response to hot rocks,
due to ground influence, the aforementioned valuable objects with interference vectors
close to hot rocks can be missed. This disadvantage is eliminated by the NHR-algorithm.
Identification of flat iron objects
Such objects include steel beer caps, pieces of roof layers, pieces of cast iron and
so on. These are the objects causing most identification difficulties and they are often
mistaken for nonferrous objects, such as coins. The right identification of such targets
shall be provided by the SSF algorithm, as it was mentioned. Remember, that this
algorithm requires wide scanning sweeps.
Nevertheless, there is a range of technical tricks that let us distinguish such
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Selective Metal Detector SOREX PRO. Operating manual.
Make additional scanning to detect object type
above the center of the object, i.e. on the maximum signal
line, keeping distance between the searchcoil and the
ground if possible. For the same purpose it is necessary to
scan found object in the direction with the least ground
relief changes. In this case the ground interference is barely
noticeable.
Single tones or tone sequences may go along with
searchcoil interaction with metal objects. Pay attention to
the following:
If detector responds by single tone short signal with
high pitch and signal level is pretty stable then there might
be a small nonferrous metal object under the searchcoil at
the 5 cm depth and deeper.
If several (3 as a rule) high pitch signals are heard it
means that same object is in the zone near the searchcoil
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