Electric CPT cones and piezocones are high-precision measuring instruments purposely developed for geotechnical soil investigation. The cones are designed, manufactured and tested in accordance with international standards.
Electric CPT cones and piezocones are available with different cross sectional surfaces, i.e. the 10 cm² and 15 cm². The cones have a subtraction type lay-out; this means that the strain gauges (sensors) measuring the cone resistance (qc) and the local sleeve friction (fs) are mounted on one single measuring body. This gives the subtraction type cones superior sturdiness over the compression type cones.
The electric CPT cones and piezocones feature a biaxial inclinometer, that is integrated in the cone body just above the conical tip. This assures rapid alarm, when the cone hits an obstacle or when it exceeds a previously set value.
A piezocone is in fact a standard electric CPT cone equipped with an extra pressure sensor enabling the cone to measure the in-situ pore pressure as an extra parameter and to do so-called dissipation tests.
The electric CPT cones measure the tip resistance (qc), the local sleeve friction (fs) and the deviation from the vertical axis in 2 directions (i). Piezocones measure these same parameters plus the insitu pore pressure and are therefore suitable for dissipation testing as well. All parameters are measured continuously and simultaneously.
The signal output from the cone is a voltage signal. It is amplified in the cone itself and transferred to the surface by means of a string of CPT sounding cables provided with gold-plated Lemo connectors. This string of cables goes to the datalogger where the analogue signal is converted into a digital signal. The digital signal is then sent to a computer for recording and further processing.
Both the electric CPT cones and piezocones can optionally be supplied with an extra sensor equipped with special modules for e.g. seismic CPT testing and alike.
All cones are temperature compensated and provided with a built-in precision strain-gauge amplifier. All cones are suitable for Class 1, 2, 3 and 4 CPT(U) testing according to ISO 22476-1 and ASTM D5778-12.