An electric CPT measuring head is a calibrated high-precision measuring instrument designed for continuous and/or discontinuous mechanical cone penetration testing. It allows for pushing in CPT sounding tubes with a diameter of 36 mm along with inner rods, and a mechanical CPT cone.
The force on the mechanical CPT cone is transferred to the surface by means of the inner rods running through the CPT sounding tubes. The measuring head converts the mechanical reaction forces transferred to the surface by these inner rods into an amplified voltage signal. This signal is diverted to the datalogger
, where the analogue signal is converted into a digital format. The digital signal is subsequently sent to a computer for recording and further processing. In this way mechanical CPT test data can be registered automatically while performing the test.
The electric measuring head is designed to be used in combination with a mechanical (friction) jacket cone
. The electric measuring head features 2 independent measuring bodies. The central measuring body measures the tip resistance (qc) and/or the local sleeve friction (fs), the other measuring body measures the total friction (ft) on the outside of the string of CPT sounding tubes.
The strain gauges (sensors) of the measuring bodies measure, in case of continuous mechanical CPT testing, the cone resistance (qc) and the total friction (ft) continuously and simultaneously. In case of discontinuous mechanical CPT testing in combination with a jacket cone, the cone resistance (qc) and the total friction (ft) are recorded intermittently. When the same discontinuous mechanical CPT test is done with a friction jacket cone (also called Begemann cone) the cone resistance (qc) and the local sleeve friction (fs) are recorded intermittently. The jacket cone allows for continuous as well as discontinuous CPT testing. The friction jacket cone allows for discontinuous CPT testing only.
Please note that the CPT measuring head suitable for continuous CPT testing differs considerably from the measuring head suitable for discontinuous CPT testing.
The advantages of an electric measuring head are numerous:
- Advanced and highly accurate measuring tool
- Allows for high productivity
- Real-time display of the measured values on the screen of the computer
- Suitable for either continuous and discontinuous mechanical CPT testing
- Robust design