Searching In Salt Water - Whites Surf PI Dual Field Instruction Manual

Chapter 4 Surf Dual Field Operation
HUNTING AT THE
SURF LINE AND
HOLDING THE LOOP
JUST ABOVE THE
WATER SURFACE
8
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Searching in Salt Water

Pulse Induction instruments do not need to be ad-
justed to ignore the effects of wet salt or ground
mineralization. When you plunge the loop into salt
water, it will take a second or two for the S.A.T. to
stabilize the detector. If you lift the loop out of the
water, you will hear a brief tone.This is a normal
function of the S.A.T. system.
If you are hunting at the surf line, simply lift the
loop just above the water as the wave comes in.
This will minimize false signals, plus it is easier to
sweep the loop in air than in water. If the loop is
dunked in salt water, then pulled out and swept on
dry land some false signals may be heard. They are
caused by the water droplets moving around on the
loop case. You can minimize these noises by treat-
ing the loop case with Armor All, silicone spray,
or spray wax. This makes it easier to shake off the
sand and excess water.
Interpreting changes in the threshold is the key to
success using the Surfmaster Dual Field. Some very
deep targets could cause a subtle beep in the normal
threshold. Identifying these subtle changes can be
challenging underwater with noise from your air
supply. Practice with known targets to become fa-
miliar with the way the threshold changes over such
sample targets.
Some threshold changes are caused by dramatic
changes in the ground, for example placing the loop
in salt water. Obvious changes in conditions are
easily recognized and the Surfmaster Dual Field
will quickly and automatically reduce the sound
back to threshold. However, less obvious changes
may result in some conditions. Decomposed iron,
for example, may respond. Such signals must be
investigated. Fortunately some idea as to the size
of a target can be determined by the size of the area
that causes the change in threshold. Remember to
keep the loop in motion so that the instrument will
continue to respond.