30 TDI
Pr o
Owner ’s Gui de
the target can be observed The Pulse Delay can be changed to optimize
sensitivity to desired targets. After you have seen how the Delay affects
the signal, you can try the same tests with the FINE GEB on (clockwise
from OFF) and the Conductivity Toggle to all. At this time you can observe
whether the target produces a high tone or a low tone. You can then
choose either the low or high settings to observe how the Conductivity
Toggle setting can eliminate or accept a target.
The important thing is that you do have control over the Pulse Delay, and
therefore over the optimization of the sensitivity of the detector to certain
desired targets. The rule of thumb would be to set the Pulse Delay at 10
uS when prospecting for small to moderate gold nuggets, and set it closer
to 25 uS when hunting on beaches for coins or relic hunting for iron and
more conductive metals such as brass.
Since the Pulse Delay setting does affect the Ground Balance process,
you must re-adjust GEB (ground balance) after changing the level of pulse
delay. Most typically only minor adjustments to FINE GEB are necessary
after minor Pulse Delay adjustments. In addition, the level of Pulse Delay
will have an affect on the ability to reject the ground, particularly wet salt
type soils.
During TDI fi eld-testing, an extreme black sand and salt water beach was
selected as the toughest ground we could fi nd. The Pulse Delay was ini-
tially set at 10 uS. At once we found that we had trouble achieving a clear
ground balance point as the extreme negative black sand and conductive
salt were reacting. The audio was too noisy to allow recognition of real
targets. Lowering the Gain helped a little, however increasing the Pulse
Delay to mid-range (around 17.5 uS) rendered the Threshold smooth, and
we could then achieve a clear Ground Balance point.
Even though a Pulse Delay of 10 uS would have been ideal for the types
of low conductive gold jewelry we hoped to fi nd, the higher Pulse Delay
allowed for improved Ground Balance, Gain, and stability, resulting in
