TDI
Pr o
Owner ’s Gui de 29
MORE ON PULSE DELAY
Sampling as close as possible to the end of the transmitted pulse gives
the highest sensitivity to all metal targets regardless of their content or
conductivity. The best signal from all targets is obtained when using a
short (10 uS) delay. However, increasing the Pulse Delay beyond 10 uS
toward 25 uS will minimize or eliminate the signal from low-conductive
targets, so that high-conductors stand out more even though they are giv-
ing out less of a signal because they are sampled further down the decay
curve. For maximum sensitivity to all targets, you would want to set the
Pulse Delay as close to 10 uS as possible for the area ground conditions
As you would expect, a nickel would fall into the same category as gold
and will be heard at 10 uS as a high tone. Larger silver and clad coins will
produce the low tone. With alloyed gold, the conductivity can vary, so the
optimum pulse delay can vary as well. Generally speaking, alloyed gold
will be seen as low conductive (high pitched tone), so will be seen best at
a lower pulse delay (10 uS ). 10k or 14k rings will usually react as low
conductive, whereas a purer gold ring, ( 22k and 24k), may react as high
conductive (low pitched tone). This can also be the case with very pure or
large gold coins and gold nuggets. A solid US $5, $10 or $20 gold coin
will usually read as high conductive, whereas, a $2 1/2 gold coin will read
low conductive. Pure gold Bullion (24k) like a one ounce Canadian Maple
Leaf will read as high conductive as well. This can be the case with a very
large gold nugget or a very pure or high gold content nugget, Fortunately,
most gold nuggets are of mixed alloy and fall into the low conductive cat-
egory. Most U.S. gold nuggets read as low conductive, thus producing the
familiar high tone. However, most Alaska and Australian gold which is over
90% gold will read as high conductive with a low sound.
The size and shape (surface area) of the target has a bearing on the
optimum setting for the Pulse Delay. It is recommended to experiment with
different targets at different Pulse Delay settings. This is best done with
the FINE GEB off, so that all targets sound the same, and the sensitivity to
