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Two high-torque stepper motors were used to drive the penetrometer and shearometer moving carriages in the vertical axis direction while another one low-torque stepper motor was used to drive the rotating spindle of the shearometer. The motion controls for the penetrometer–shearometer unit were performed by the programmable logic controller (PLC) unit and other external electronics and sensing devices. The overall construction of the unit was made up of the main frame to support the moving carriage sub-assemblies, two moving carriage sub-assemblies to support penetrometer and shearometer, the gear driving mechanisms to support the traverse movements of the moving carriages, and the three-point hitch attachment to support the main frame and provide attachment to the tractor. The automated soil penetrometer–shearometer unit utilises both commercial penetrometer and shearometer. A tractor-mounted, automated soil penetrometer–shearometer unit was designed and developed for the purpose of simultaneous in situ measurements of soil penetration resistance and shear stress.