User's Manual
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a. Use automatic range gain When this is selected the program automatically
increases gain with increasing range to compensate for signal attenuation with
range. The gain profile is automatically readjusted at the start of each line.
b. Automatic zero time
Use this setting to move the first arrival to the beginning of
the plot.
c. Antenna combination For the Pavement Scanner, this should always be set to
TxA RxA.
d. Depth/Time units Select the units for the vertical scale on the B-scan. The most
basic units are sample number (Samples). Sample number multiplied by the
digitizer sample period gives sample time (Nanoseconds). Sample time
multiplied by the medium velocity gives distance (Centimeters
, Inches, Meters,
Feet).
e. Depth/Time range Users can opt to display the full range, half range, quarter
range, or eighth range. Users may wish to display only a shallow portion of the
usable range when interested in the more shallow portions of the surveyed range
(depth).
f. Velocity of medium The velocity of EM waves is dependent on the material type.
In order to properly convert from time of flight to depth, the velocity of the
medium must selected (see Depth/Time units above). Select the medium type
and the corresponding dielectric constant. The EM velocity is
εν
/c= where v
is the EM wave velocity, c is the speed of light in a vacuum, and ε is the dielectric
constant of the medium.
Air
ε = 1
Dry concrete/indoor/mature - Dry soil
ε = 4
Damp concrete/outdoor - Damp soil
ε = 6.5
Moist concrete/outdoor/young - Moist soil
ε = 9
Wet concrete/outdoor/young - Wet soil
ε = 16
Saturated concrete/outdoor - Saturated soil
ε = 25
g. Distance units Select the units for the horizontal scale on the B-scan
(Centimeters, Inches, Meters, Feet, Seconds).
h. Distance range Select the horizontal range of the B-scan in distance units (10,
20, 50, 100, 200).