The Clegg Impact Soil Tester type CIST/882 provides a means of measuring and controlling soil strength and consolidation levels during trench re-instatement. It is also used to confirm uniform compaction over wide areas of ground, identifying poorly compacted areas and ineffective rolling of materials.
The Clegg Tester consists of a 4.5kg compaction hammer operating within a vertical guide tube. When the hammer is released from a fixed height, it falls through the tube strikes the surface under test, decelerating at a rate determined by the stiffness of the material within the region of impact. A precision accelerometer mounted on the hammer generates an electrical charge which is fed by a cable to a hand held digital readout unit.
The fast microcontroller in the readout scans and filters the signal and registers the deceleration in units of Impact Value (IV) up to 100 IV. The IV is an indication of soil strength and shows good correlation with results from CBR tests. Data from Impact Soil Tester can therefore be used in a similar manner to results from CBR tests performed in the laboratory and in the field. The Tester is powered by a single 9V PP3 battery located in a small pull-out drawer in the readout unit.