TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
27
SEARCH TECHNIQUES (continued)
Narrow It Down
To narrow the response further, position the searchcoil near the center of the response
pattern, release the trigger, and then pull it again. Now you will only hear a response
when the searchcoil is right over the top of the target. Repeat this procedure to narrow
the zone even further. Each time you repeat the procedure, the field of detection will
narrow further.
Estimating Target SIZE, DEPTH, and SHAPE
When the trigger is pulled to activate Pinpoint, the LCD displays estimated depth. The
estimate is based on the presumption that it is a coin-sized target.
But what if it is not a coin-sized target? The most common example is that of an aluminum can.
Flattened aluminum cans are usually identified as dimes or quarters. Their large size will
produce a strong signal, tricking the microcomputer into thinking that it is a shallow coin.
The following technique differentiates buried aluminum cans from coins. Sweep back and forth
to get a feel for the target, keeping the searchcoil close to the ground. Now, continue to sweep
back and forth as you slowly raise the searchcoil higher and higher. If the response
diminishes quickly and never gets very broad, the target is probably a coin. If the response
diminishes slowly as you lift the searchcoil, and you get a broad response, the target is
probably an aluminum can. Practice this by laying a coin and a flattened aluminum can on the
ground; you will quickly understand how to differentiate the two and will probably never have
to dig another aluminum can again. And, you will know whether it was deep or shallow. This
technique works well in the All Metal Mode, and to a lesser extent in Discrimination Mode.
Objects which are ring-shaped, or flat and round like coins, tend to give a narrower, crisper
response than objects of similar size with irregular shapes. The easiest way to demonstrate
this is with an aluminum screw cap from a soda bottle. In its normal shape, it occupies a
volume, and gives a somewhat broader response than that of a coin. But if you flatten it, the
response will be crisper and more like that of a coin. Again, these differences are most readily
noticed in All Metal Mode.
Long skinny iron or steel objects such as nails usually produce a double response when
scanned lengthwise, and a weaker single response when scanned crossways. This is most
noticeable in the All Metal Mode. However, a coin lying on its edge can produce a similar
response, so rely on both the Target-ID as well as
target feel
to distinguish between different
kinds of objects. Objects within 2 to 3 inches of the searchcoil will often produce multiple
responses as you sweep across them, because the response field close to the searchcoil is
irregular.
