A multi-sensing device with a piezoresistive pressure sensor for hydraulic system control was developed, applied to a hydraulic belt conveyor and tested. The following variables were measured and could be analyzed: speed, torque, absolute displacement, horsepower, pressure, oil flow rate, mass flow rate of conveyed materials and even malfunction diagnosis. The concept may have applications in automated payload measuring on cargo aircraft, although the primary interest was for agricultural applications. Hydraulic motor speeds with high resolutions were measured. Also, relationships between mass flow rates on the conveyor belt and required torque due to loading under various situations were presented. A formula for calculating effective belt tension was developed and could be used to control mass flow by measuring the change in motor torque. This multi-sensing device and control system would be applied to any hydraulic system with hydraulic motors.