design, construction and field evaluation of a tractor-mounted penetrometer

soil compaction is an important aspect of agriculture and different methods are available to measure this parameter. one method is called the cone index; measuring the force required per unit area for penetration of a standard steel cone into the ground. cone penetrometers are used for cone index measurement. in this study, a tractor mounted, hydraulically-operated penetrometer was designed, built and evaluated. the penetrometer consisted of a frame, hydraulic driving unit, force transducer, depth measuring unit and data acquisition system. the entire penetrometer unit was mounted on the frame and held in place by the three-point hitch on a category iii tractor. the hydraulic driving unit provided a constant penetration rate of 3 cm/s, in accordance with the asae s313.3 standard. a cantilever beam strain-gauge load cell measured the penetration force applied to the cone shaft and a photodiode sensor measured the penetration depth. a microcontroller-based data acquisition system was designed and developed to record and save the penetration data. evaluations were conducted by comparing the data of the tractor- mounted penetrometer and that of a commercial hand-pushed penetrometer (eijkelkamp). analysis found no significant difference at the 95% confidence level. the penetrometer performance was found to be reliable and the unit’s mechanical and electronic parts worked without malfunction.