Thanks for the help. For those that are interested, here is David Johnson advice at First Texas. details. Circle C Digger
Sean,
Aluminum scrap (typically "canslaw" caused by lawnmowers chopping up
aluminum cans), if it's more than 2-3 inches across, often reads in the
high numbers because of its high conductivity. Flat pieces of iron for
instance steel bottle caps (esp. if rusted) can read in the high numbers
because of the way the magnetic field gradient changes as you pass over
the target. In areas where these kinds of targets present a serious
problem, there are several ways to deal with it:
1. As you sweep back and forth across a coin, the readings will usually
be fairly consistent, whereas the readings from trash targets will
usually bounce around a lot.
2. The 3B and dP tone selections use a sampling method that tends to
drop the tone on flat iron, and makes the readings on trash targets more
inconsistent ("non-repeatable"). The dP tone selection also tends to
give a slight "squawk" sound on flat iron which you won't usually hear
on a good target.
3. As you raise the searchcoil above a coin, the reading will tend to
stay the same, whereas the reading over flat iron will usually drop.
4. If you sweep the heel of the searchcoil over the target, a coin will
usually still register consistently, whereas trash targets esp. flat
iron will tend to become inconsistent.
5. When crisscrossing the target in an "X" pattern, coins will usually
give about the same reading all around, whereas trash targets will
usually give responses that vary with the direction of the sweep.
6. In lightly mineralized soil, the iron mineral bargraph will usually
jump up a bar or two over shallow steel bottlecaps, whereas that doesn't
happen over coins. Some T2 users have found this technique quite useful
for identifying iron trash that's reading in the high coins range.
The Teknetics T2 is equipped with a double-D searchcoil. This type of
searchcoil is more difficult to manufacture than a concentric type coil,
but is usually found on the more expensive metal detectors because the
overall performance is better. However the shape of the magnetic field
of a double-D searchcoil which is advantageous under most conditions,
tends to have difficulty discriminating flat iron. This is a general
characteristic of double-D searchcoils and is not unique to the
Teknetics T2. ...... Nonetheless, most users of machines that have
double-D searchcoils do a little experimentation and quickly find
techniques which work for them, so that they can avoid digging trash
objects.
If you're not active on the Teknetics T2 forum you might want to check
it out. The URL is: http://www.findmall.com/list.php?58
I hope this is helpful. Enjoy your T2!
--Dave Johnson
Chief Designer
First Texas Products
