White’s Electronics Spectra VX3 - Manual (Page 70)

Page 6-7
Spectra VX 3 User’s Guide
The right side of the screen reports the phase and strength of
the residual signal
2
, and does so for each individual frequency
3
.
This is useful for analyzing the characteristics of the ground,
but only if the residual signal consists purely of ground signal.
This will be true if (1) we can get rid of other residual signals
like an imperfect loop null, and (2) if we put the loop over tar-
get-free ground. To get rid of any residual loop null signal, hold
the loop in the air (and away from metal, natch),
TAB to select
the Zero button, and press ENTER . Ground Probe is now zeroed,
and you should see the Strength numbers go to 0% and the
phase numbers jump around a lot:
Now you can lower the loop to the ground, careful to avoid
targets, and the Phase and Strength numbers will be that of the
ground. VX
3 is calibrated at the factory to a ferrite sample,
which ideally should read 178°. Most ground mineralization
should read close to that
4
.
2. Whereas the Sensitivity Probe screen only show a composite
residual signal strength.
3. Of course, in single-frequency mode only that frequency is
reported.
4. In Chapter 1 ground phase was described as being close to 0°.
Now we say it’s close to 180°! Actually, 0° is “scientifically”
correct, but the VX
3 programmers like to do things backwards.