White Spectra VX3 Instrukcja Obsługi Pobierz pdf (Strona 14)

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Spectra VX

User’s Guide

reaction. A so-called “induction-balanced” coil arrangement

prevents the receive coil from being overwhelmed by the trans-

mit signal, allowing it to see very small target signals.

Phase & VDI

Practically all VLF-IB detectors operate as phase discrimi-

nators. The received signal is converted to phase, and the phase

is a strong indication of what the target might be. The particular

phase of a target can vary with the frequency of the transmitted

signal, so different detectors designed to use different frequen-

cies can report completely different phase results.

To keep users from having to learn all these different phase

response scales, White’s has chosen to normalize them all to a

standard “VDI” scale. VDI stands for Visual Discrimination

Indicator and is simply a consistent numerical value assigned to

targets regardless of the frequency being used. Therefore, a US

nickel detected with a 6kHz detector will have the same VDI as

with a 15kHz detector. For historical reasons, the standard VDI

scale is based on a 6.592kHz detector and is shown below.

The ability to separate targets by VDI is what allows a

detector to discriminate. Targets with a negative VDI are usu-

ally ferrous (iron), and targets with a positive VDI are usually

non-ferrous. Small gold tends to have low VDI’s while thick sil-

ver coins have high VDI’s. Other targets like cupro-nickel

coins, brass and bronze relics, and aluminum trash can have

wildly varying VDI’s depending on their alloy, size, and thick-

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 87 88

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White Spectra VX3 Instrukcja Obsługi Strona 14