Dynamic Function Test; Reference Sbg - Geometrics MetalMapper 2x2 Operation Manual

Where f and r are the 'monostatic' (concentric) X, Y, and Z background corrected responses
t t
from the current and reference function tests, respectively. Concentric corrected responses are
the measurements in each receiver channel (X, Y, and Z) when the same transmitter coil fires;
for example responses in A Rx when A Tx fires, B Rx when B Tx fires, etc. The threshold T is set
so that variation due to noise is accepted but variation due to misplacement of the function test
object or to electronic failure is flagged.
It is possible for users to create their own master SFT files if needed. Navigate the cart to a
clean area that is known to be free of metal scrap. Collect an SBG measurement. Place the test
object into the holster and collect an SFT measurement. This collected SFT file can be used as a
future SFT reference measurement.

5.2 Dynamic Function Test

The dynamic function test feature has been removed from the acquisition software beginning
with version 1.0.1069. If the software still prompts for this mode please contact the factory to
update the software.

5.3 Reference SBG

This QC feature warns the operator if the amplitudes of a static background measurement have
changed by a defined ratio over the course of a survey. The operator selects the time gate
windows used for the comparison, and the ratio by which these can vary before a warning is
displayed. At the beginning of a survey at a new site, a reference SBG file is created by taking a
SBG at a known clean area free of metallic debris. This file is loaded as the "Reference SBG" in
the QC settings.
Every additional background collected throughout the survey at the site will be compared to
this reference SBG file. If the measured amplitudes during the defined time gates are either 5x
greater or 5x smaller, a warning is displayed to the user that the Background has Drifted:
If this SBG measurement was made at a known clean location then the soil conditions have
changed significantly from the reference background. If this is a background at a new location,
it is possible that there is metal contamination at the current location, or metal contamination
at the reference SBG location. For the importance of collecting valid backgrounds, please refer
to the Technical Bulletin at the end of the manual.
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