Velleman CS102 Mode D'emploi page 5

Receiver
•
The receiver is another coil of wire that is located inside the search coil and which is constructed in such a
way that the magnetic field of the transmitting coil does not induce current in it. Magnetic fields from
nearby metallic objects however will produce an electric current in the receiver coil.
Phase shift
•
The signal received from the receiving coil will usually be delayed versus the transmitted signal due to the
tendency of conductors to impede changes in the flow of current, the so called inductance. The delay is
referred to as phase shift. Metal objects that are primarily inductive e.g. large thick objects made of good
conductors (gold, silver, copper...) will result in large phase shifts, whereas metal objects that are primarily
resistive e.g. smaller thin objects made of less conductive materials will result only in minor phase shifts.
Refer to the table below for a short overview of the electrical conductivity of some materials.
Material
silver
copper
gold
aluminium
calcium
zinc
Note that detection also depends on the size, shape, depth... of the metal.
•
Ferromagnetic
•
Substances that usually conduct very poorly or not at all can become magnetized when inside a magnetic
field, resulting in a strong signal picked up by the receiver. However, this signal shows little or no phase
shift. Soils containing small grains of iron-bearing minerals will show ferromagnetic characteristics.
Discrimination
•
Since any given metal will respond with its own characteristic phase shift, it will be possible to distinct
between them. The process of distinguishing between different metals is called discrimination.
Ground balance
•
As mentioned earlier, soils that contain iron will produce a response signal which can be a lot stronger than
the signal produced by a metallic object concealed in it. This is also the case for places where ground water
contains a lot of dissolved salt.
•
However, the phase shift caused by the ground, the ground effect, remains fairly constant over a limited
area when the search head is kept at a steady height.
•
Accurate ground balance makes it possible to precisely pin-point the location and depth of an object. It is
essential when working in 'all metal' mode.
7. Preparation
•
Prior to use, the CS102 must be assembled.
•
Mount the search coil [M] on the lower shaft [K]. Push the bolt through the holes and tighten with the nut
knob [L]. Do not tighten the search coil fixation too hard e.g. do not use pliers or other tools.
•
Slide the extension shaft [G] into the control shaft [B]. Rotate the extension shaft [G] until the spring-
loaded buttons snap into place.
•
Line up the spring-loaded buttons [I] of the lower shaft [K] with the holes in the extension shaft [G]. Slide
the lower shaft [K] into the extension shaft [G].
•
To determine the ideal shaft length, stand upright holding the metal detector by the handle [B] and your
arm on the arm rest [A]. When holding your arm relaxed next to your body, the search coil [M] should be
about ½" to 2" (max.) above the ground. To adjust the length, press on the spring-loaded button [I] and
move the lower shaft [K] to the desired length.
•
Turn the locking nut [J] counter clockwise (top view) to secure the lower shaft.
•
Loosen the search coil fixation knob, adjust the search coil [M] so it is parallel to the ground and tighten
the nut knob.
•
Wind the cable [H] around the shaft, leaving enough slack. Insert the plug into the 5-pin input jack [F].
The slotted connector only fits in one way, do not force.
•
Insert batteries (see §14).
V. 03 – 09/08/2021
CS102
Electrical
conductivity (S/m)
6
63.01 × 10
6
59.6 × 10
6
45.2 × 10
6
37.8 × 10
6
29.8 × 10
6
16.6 × 10
5
Material
conductivity (S/m)
nickel
iron
platinum
tin
sea water
drinking water
Electrical
6
14.3 × 10
6
9.93 × 10
6
9.66 × 10
6
9.17 × 10
4.788
0.0005 ~ 0.05
©Velleman nv