
DPN 402197 © TSS (International) Ltd Page 5 of 14
3.2.2 Sensing Coils
Each sensing coil in the array detects the alternating magnetic fields associated with
the tone current in the cable, and supplies an output voltage to the SEP proportional
in amplitude to the received magnetic field strength. Because the output voltage is
derived from the tone on the cable, it is at the same frequency. Circuitry within each
sensing coil applies signal conditioning and pre-amplification.
CAUTION
The waterproof characteristics of the coils might degrade if you open them.
The pre-amplifier boards contain no user-serviceable parts. To avoid degrading the
depth rating of the sensing coils, do not remove their end-caps.
All vertical range measurements to the target position are relative to the coil reference
line. This line, shown in Figure 3–2, joins the centres of the port and the starboard lat-
eral coils.
Measurements of lateral offset are relative to the centre of the coil array and are pos-
itive if the target is to starboard and negative if it is to port.
Figure 3–2: The coil array reference line
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