
350 Cable Survey System
DPN 402197 © TSS (International) Ltd Page 6 of 10
Figure A–5 shows the relationship that exists between the signal voltage v received
by the coil in Figure A–4 and the angle
φ
between the coil and the conductor:
❐ There will be no output (a null condition) when the conductor lies along the major
axis of the sensing coil (φ = 90° or φ = 270°).
❐ There will be maximum output when the conductor is on a line perpendicular to
the major axis (φ = 0° or φ = 180°).
❐ In all other conditions the coil output will be at some intermediate value between
maximum and zero as defined in Figure A–5.
The 350 System uses two coils arranged at right angles to extend the coverage
through a full 360°. By comparing the relative outputs from the two coils, the System
can determine the angle between the centre of the coil pair and the target as shown in
Figure A–6.
Figure A–6: Determination of relative angle using two coil voltages
In Figure A–6 the two independent windings of the coil assembly supply signal volt-
ages v
x
(lateral coil) and v
z
(vertical coil). The System uses these to derive the angle
φ
between the coil assembly and the conductor:
Since TSS calibrates and matches the coil windings during manufacture, any
changes to the tone frequency or current will have an equal effect on all coils. The
ratio of their output voltages (and therefore the evaluation of
φ
) will therefore remain
constant.
v φcos∝
φtan
v
x
v
z
----=
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