Sensors & Software CONQUEST 100, User Manual

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Conquest 100 Principles of Operation
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Figure 2-5: The image shows a flat response from the top of a rebar running in the same direction as the Line Scan.
The flat response from the bottom of concrete is also indicated. The data image also contains 3 hyperbolas produced
by crossing rebar perpendicularly
2.3 Concrete Cal
T
he “Concrete Cal” parameter is a measure of the velocity with which the radar signals travel
through the concrete. The Concrete Cal is determined automatically based on the shape and
positioning of hyperbolas. An accurate Concrete Cal is required for reliable depth estimates and
depth slice images.
The user must set the Concrete Cal at each site for accurate depth measurements ( Section
6.8.6). This can be determined once some GPR Lines have been acquired. Crossing the target
perpendicularly is important to ensure an accurate Concrete Cal value.
The Concrete Cal number typically varies from 85 to 130 depending on moisture content,
percentage of air entrapment, addition of fly ash or other admixtures and the aggregate size.