Abstract
For the on-line measurement of stress and energy distributions inside ball mills, two types of self-contained, autonomous grinding balls with fully integrated piezo-electric sensors and data-processing electronics are developed and fabricated. The basic model is designed for batchwise experiments on ball mills, where data registered in electronic memories are read out through cable connections to a processing circuit. The improved model contains additional data modulation circuits with a VHF microtransmitter, allowing on-line data retrieval. For the purpose of circuit miniaturization, hybrid and surface mount techniques (SMT) have been utilized. The instrumented balls are identical in size, mass and surface characteristics to the normal grinding balls, with the minimum outer diameter being 40 mm. Systematic experiments have shown that they are fully applicable in a realistic grinding environment where grinding media are presented. In addition to ball mill applications, the developed integration and measuring technique is generally suited for on-line data registration on free-moving objects or other industrial applications where accessibility of the measurand is insufficient.