ABSTRACT AN instrumentation system was developed and installed on a trailed tool bar subsoiler to record six operating parameters of deep tillage performed to depths of 1.0 m. The system used a microprocessor to record the horizontal force, the vertical force and the moment in the plane of these forces as applied to one time. Wheel speed, total draft and operating depth were also recorded. The data were recorded at 100 Hz and stored on magnetic tape for analysis and by an ultraviolet chart recorder for field verification. The system performed satisfactorily except for the proximity switch method used to measure wheel speed which was found to be sensitive to shock and vibration.