TEKNETICS
Comprehensive Operating Manual & Guide to Metal Detecting
19
LCD VISUAL DISPLAY
In normal operation, when the searchcoil passes over a metal object, the electrical signature
(2-digit ID) of the metal object is displayed on the numeric display for 4 seconds, unless
superceded by another object sooner. On a given buried object, the number will bounce
around if the signal is weak or if the amount of ground mineralization is high.
At the top of the display, an arrow indicates the classification of the object.
NUMERIC TARGET-ID (2-digits)
The
following table
shows the numbers typically associated with certain commonly
encountered nonferrous metal objects. Older silver U.S. coins usually read about the same as
their modern clad equivalents. Modern quarter-sized dollar coins like the Susan B. Anthony
and the Sacagawea read about the same as a quarter. Many Canadian coins are minted from
a magnetic nickel alloy which gives very inconsistent readings and may register as iron. Most
one-ounce silver bullion coins will fall into the same range as the modern U.S. $1 Eagle.
OBJECT TARGET-ID
foil from gum wrapper 40 - 55
U.S. nickel (5¢ coin) typically 58
aluminum pull-tab 60 - 75
aluminum screwcap 70 - 80
zinc penny (dated after 1982) typically 78
aluminum soda pop can 75 - 85
copper penny, clad dime typically 83
U.S. quarter (25¢ coin), clad typically 89
50¢ coin, modern clad typically 92
old silver dollar coin typically 94
US silver Eagle $1 coin typically 95
PROBABLE TARGET-ID
The probable Target-ID zones at the top of the LCD display represent the signal ranges
produced by various coins and types of metal objects. When a metal target is detected, the
microcomputer analyzes the signal and categorizes it based on what kinds of metal objects
usually produce that kind of signal. The microprocessor then displays an arrow along the top
of the LCD screen above the icon which represents that category.
For instance, if the detected signal fits within the parameters usually exhibited by zinc pennies
and the electrically similar aluminum screw caps, the microcomputer will categorize the signal
as “zinc penny/aluminum screw cap”. The LCD screen will then illuminate the arrow above the
zinc/screw cap icon.
Copper pennies (pre-1982) will usually register in the 10¢ zone.
Most gold jewelry is small, and will tend to read in the 40-60 range. Silver jewelry usually has
more metal in it and therefore tends to produce higher readings.
Since different metal objects can produce similar signals, and since minerals in the soil can
distort the signals, the probable Target-ID’s are just that — probable. There is no way of
knowing for sure what’s buried other than to dig it up. Experienced metal detector users have
a rule of thumb — “when in doubt, dig”.