Principles Of Pulse Induction - Whites TDI SL Owner's Manual

Principles of Pulse Induction

Pulse induction (PI) detectors are very different from tradi-
tional induction-balance (VLF) designs. Instead of transmitting
a continuous-wave magnetic field, the PI detector periodically
transmits brief impulses of magnetic energy. The PI receiver
then looks at the impulse decay for target (and ground) informa-
tion.
TX
RX
The use of high-powered impulses results in better ground
penetration than VLF, especially in highly mineralized soil.
This makes the PI detector the best choice for certain kinds of
hunting in bad ground where many VLFs simply won't work.
There is no traditional discriminator in PI detectors,
although there is some ability to discern certain types of metals.
The decay response varies with target conductivity (plus other
characteristics) so that low conductive targets have a fast decay
and high conductive targets have a slow decay:
No target
The Pulse Delay control, which determines the point where
the decay is sampled, can be used to eliminate low conductive
targets such as thin foil. Further increasing the delay can knock
TDI SL
Owner's Manual
Pulse Rate
Exponential decay
Raw Response
Page 7
Low-conductive
target, fast decay
High-conductive
target, long decay