Copyright 2005, Dankowski Detectors. All rights reserved.
Head-To-Head Comparison Testing
by: Thomas Dankowski
Drafted May, 2006
One person claims 7" on a dime in one State and another person claims 12" on a dime in another State. One person hunts a
particular site with Brand-X detector, then, the very next day, he hunts the exact place again with Brand-Y detector and
finds more good targets, then touts the Brand-X detector as inferior. These are very common and misleading occurrences.
A head-to-head comparison is VERY difficult to perform. Absolutely ALL variables must be removed if any form
of validity is to be ascertained. The slightest changing variable can completely void the test. --- Let's get dirty and
come away clean.
A textbook perfect test-garden is a good start, yet it does not represent the real world dirt conditions. This includes
simplex and complex test-garden scenarios. The preferred method for head-to-head comparison takes place at several different
sites with varying mineralization and with several different undug, undisturbed targets in their natural settings.
Let's say you have selected a local park. You have located several 'items of interest' and marked their exact pinpoint
location with colored plastic poker chips. You turn off Brand-X detector and swap it out for Brand-Y detector. Here is where
the difficulty begins. Was Brand-X detector control panel settings optimized for each individual target?
Was the level & quality of signal documented (for comparison) on each individual target..... or are you ONLY seeking
to find 'detectable' or 'not detectable' (go/no-go) scenarios to each detector being tested...... regardless of signal
strength/quality? How high was the coil over the target(s)? How fast was the coil sweep speed? Are you aware that one
detector may like a fast sweep speed.... and the other unit resolves better with a slower sweep speed? Were you facing the
exact same direction when sweeping the coil over subject target? Was Brand-Y detector coil sweeping the subject target one
inch further forward or aft of the exact pinpoint location? Was only one of the units properly ground balanced? Is this type
of information potentially "interpretive"? Are you slightly biased more favorably towards Brand-X detector? Does Brand-Ex
detector come standard with a 10.5" coil and Brand-Z detector is factory 8" coil equipped? What is categorized as 'fair' or
'unfair'? When you went back to the car to swap detectors, did the nearby local radio station switch from nighttime 10KW to
daytime 50KW transmit power? Or did the A/C compressor and pool pump cycle 'on' at the nearby building? Were your steel-toe
shoes and steel shovel a bit closer to the coil of Brand-X whilst comparing detectors? Is Brand-T detector more resonant on
low conductors (nickels) and Brand-Z detector more resonant on high conductors (silver dimes)? Does one brand
detector fall flat on its face in bad ground, yet it will trump all other detectors in fairly mineral-free dirt ---- and
you only gave it one chance at one location ---- and came to one final
conclusion? Are you trying to compare Brand-T detector equipped with an extremely tight electromagnetic footprint bi-axial
elliptical DD coil to Brand-Z detector with a concentric coplanar coil? Are you seeking to find which detector is simply the
deepest unit -- or which one presents the best enhanced adjacent target separation characteristics? Are you aware that one
detector may be superior at finding coins next to pull-tabs (non-ferrous) trash and another detector may be superior at
finding those same coins next to nails (ferrous) trash? Is one person operating Brand-X unit and a different person
operating Brand-Y unit? Can you see where this might make a difference? Did you know that you can mark targets today --- and
tomorrow you may or may not be able to detect these exact same targets? If tomorrow brings different humidity, temperature,
rain or electrical interference, did you know that a whole new set of parameters exists? Are you aware that one detector may
find one set of targets and another detector may find a completely different set of targets in the same field? Does this
make one unit inferior/superior to another unit?
This brings up another interesting scenario/phenomenon. Say a [very small nail] is 6" deep --- and a
silver dime is directly beneath the nail, one inch deeper -- at a total depth of 7". In your hands, you have one
detector and two coils; a 5" coil and a 10.5" coil. With the small coil installed, the 6" deep nail is a moderate signal
strength -- and the (one inch deeper) 7" deep dime is starting to "push the depth limits" of the small coil, yet still
within detectable range; HOWEVER, the dimes signal strength to the small coil is much weaker than the shallower nail --- so
the detector reports "iron". A one inch deeper depth to the small coil is a formidable signal strength reduction.
x-x-x-x-x Now you install the large 10.5" coil. A target at 6" and a target at 7" is hardly even a difference to
the larger coil --- the field intensity at 6" & 7" are nearly the same; HOWEVER, the detector reports "coin" because the
dime has a larger mass as compared to the [very small nail]. Sometimes this phenomenon is referred to as the
"wrap-around" effect. So, is this apples-to-apples... head-to-head comparison? Interpretive it is! In any case, being armed
with this knowledge can prove to be VERY fruitful. The same detector with different coils may 'light up' completely
different targets in the same area. Keep that in mind.
As you can see, there are many things that can alter data resultants. One of the more common mistakes is to be facing, say
West (270 deg.) while sweeping with Brand-X, then repeat the same process with Brand-Y detector in almost exactly the same
direction, nearly due West (say 255 deg.). This slightly different (15 deg. difference) sweep angle, in many cases, is just
enough of a difference to invalidate the comparison. A tight footprint DD coil can highly accentuate this common occurrence
as you rotate your body around the target. This is also to say that you may have hunted a parcel of land numerous times,
always walking South to North (facing North), yet you keep finding more targets. Maybe a particular target could only be
electromagnetically illuminated when the coil is passed over the target from a Northwest-to-Southeast approach angle. One
day you are facing (and walking) North again, but, this particular time the target is on your Right side of your sweep
(vs. directly in front of you or slightly to the Left side); hence, your coil approach angle into the target is finally the
correct angle and - "Bam" you get a good hit. Upon further examination, you decide to rotate your body around this specific
target while sweeping --- only to discover that this particular target is detectable in a certain window-of-opportunity of
body rotation --- and is undetectable from other approach angles,,,, possibly due to a co-located trash target in close
proximity to the good target. You may or may not be able to hear the culprit trash item, because of masking, silent masking
or your level of discrimination dialed in to your detector. (If you have tone ID capabilities, use zero discrimination for
the full intelligence package of existing dirt scenarios). Depending upon how your coil approaches into the co-located
targets, dictates how the detector will respond.
Find the right tool for the right job. Detectors are akin to eye-glasses. There are spectacles for specific tasks such
as; near-sightedness, far-sightedness, high magnification macro viewing, long-range zoom viewing, reading glasses, 3-D
viewing, Solar eclipse viewing, low-light/night-vision viewing, Sun shades and shades that are specifically designed for
nothing ... except to just simply look "cool". And detectors with 'flames' to just simply look ****** ,,,,, you know the
rest of the story!
All of this information sounds like 'data overload'. There are many additional scenarios that can void a head-to-head test.
Sounds discouraging and difficult, doesn't it? The bottom line is; DO YOUR BEST! Remove as many of the variables as
possible. If you can have your buddy standing behind you ,,, handing you detectors and equipment,,,, whilst you have your
feet planted in the exact same unmovable spot........ chances are your head-to-head testing should generate valid
results --- as sweep angle direction, temperature, ground moisture content, humidity, local electromagnetic interference,
local ground mineralization content and other potential "variables" become "constants". When you become accustomed to this
procedure,,,,, you will learn that it was not that difficult after all!!! Your conclusive analysis may very well present a
resultant that is not in accord with your initial expectations. Keep an open mind and don't be biased ....and enhanced
performance will ensue. Your increased awareness and intelligence will 'magically' increase your volume of "keeper" finds!!!