The basic principle behind the Clegg Impact Soil Tester is to obtain a measurement of the deceleration of a free falling mass (hammer) from a set height onto a surface under the device. The impact of the hammer produces an electrical pulse, which is converted into a Clegg Impact Value (CIV).
Four successive blows of the hammer on the same spot constitues one test with the peak CIV output to the digital display. The CIV is displayed in units of tens of gravities. This value correlates to the California Bearing Ratio, Texas Class Number, Elastic Modulus, and PSI. Reference ASTM test methods D5874 and F1702.
The Clegg offers the convenience of rapidly scanning compaction variation over large areas. In research studies, 250 tests were performed with the Clegg in a half-day.

1. Select a level surface (If needed, lightly scuffing surface with a foot to level the strike area)
2. The guide tube is set into position, secure by placing a foot on the tube's basee flange and steadied with the lower leg and knee)
3. The ON/RESET button on the control box is pressed and release to activate the circuitry. The hamer is raised to the drop height indicator mark
4. The hammer is released allowing it to fall freely and cleanly
5. Without moving the guide tube or pressing the ON/RESET button, the Hammer is raised o the mark and release three more times
6. The value (CIV) dsplayed after the fourth blow is recorded and the display automatically powers down 30 sec. after activation
7. Move to the next test site.