Troxler 3411-B, Manual Of Operation And Instruction

Page: 98 / 109

Appendix D-2
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n
t
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S
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p
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Backscatter Density Fast Normal Slow
Precision at 2000 kg/m
3
(125 pcf)
16.6
1.04
8.30
0.52
4.15
0.26
±kg/m 3
±pcf
Depth of Measurement (98%) 100 mm (4 inches)
Direct Trans. Density Fast Normal Slow
Precision at 2000 kg/m
3
(125 pcf)
9.38
0.59
4.69
0.29
2.35
0.15
±kg/m
3
±pcf
Depth of Measurement 50-300 mm (2-12 inches)
Moisture Content Fast Normal Slow
Precision at 250 kg/m
3
(15.6 pcf)
11
0.69
5.50
0.34
2.75
0.17
±kg/m 3
±pcf
The precisions stated are the standard deviation of 20 tests for
an average gauge. The precision defines the repeatability of
measurement.
There are two other factors that affect accuracy of nuclear
gauges on soils and asphalt: chemical composition and surface
roughness.
For backscatter density measurement, the maximum bias due to
chemical composition for soil or asphalt is 40 kg/m
3
(2.50 pcf).
For direct transmission density measurement, the maximum
bias is 22 kg/m
3
(1.40 pcf). Pure granite represents the
maximum of a material on which the gauge will read low. Pure
limestone represents the maximum of a material on which the
gauge will read high.