Geophysical Survey Systems, Inc.
SIR® 4000
Manual
MN72-433 Rev F
98
•
Power Mode can be set to 0, 50 or 60.
o
Power Mode is a passive detection method that can locate the AC current
of energized cables that are under load. These frequencies are typically
50Hz or 60Hz.
•
Frequency Mode can be set to a wide range of frequencies. Choose the option
that matches your signal application device.
o
Frequency Mode is an active detection method used in combination with a user-supplied
signal application device. Set the value of Frequency Mode to match the frequency of the
applied signal.
Process Menu: 350HS and 300/800DF
1
Gain Mode and Edit Gain Curve:
In the O-
Scope window the gain curve is the thin red line
superimposed over the scan. The centerline of the
scan is zero, to the left of it is negative
(decreasing gain) and to the right is positive
(increasing gain). To model signal loss, gain is
applied in decibels (dB) along an exponential
function. Your goal should be to have a gain
curve that creates a scan trace with balanced
amplitude changes from top to bottom.
2
Select Auto Gain Mode:
If Auto Gain Mode is
already selected, press the Init control button at
the bottom of the screen to apply an automatic
gain curve to the current scan trace. This will re-
initialize the system and add/subtract gain to
produce a visible signal. Move the antenna and
look for evidence of clipping. If your data
becomes clipped, leave the antenna in place and
re-initialize by pressing the Init control button.
This will decrease the gains so that the data will
not clip.
•
If you plan to collect multiple profiles and
wish to compare them, it is usually best to set
the gain to Manual Gain Mode once you find appropriate gain settings (you can see targets and
the signal does not clip). This will set the gain levels and they will be consistent across your
profiles. This may lead to signal clipping if you move to an area with different conditions.
•
If you are performing real-time locating, leaving the Gain Mode set to Auto will allow you to use
Init when your signal quality changes between profiles.
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