Ultrasonic sensor array for remote sensing of profiles of bulk materials

Measurement of volume and mass of bulk materials by conventional direct measurement systems (e.g. strain gauges, load cells) is limited to offline applications only and is not applicable to materials stored in partially filed containers or moving using conveyor belts. These limitations can be overcome by measuring surface profiles thus the cross section areas of a heap at subsequent cross sections and calculating the volume of the heap from these. In this paper we describe the architecture, design and experimental results for a fully prototyped cross section area measurement system that utilizes an ultrasonic sensor array operating in the pulse echo mode. The system consists of an inexpensive ultrasonic node with the component cost of less than £25 and a linear array featuring 28 12-mm ultrasonic transducers operating at 40 kHz and multiplexed to the same signal line from the node. Experimental measurements of the cross sectional area and volume of rectangular boxes exhibited the accuracy below 5%.