An instrumented ball capable of measuring a number of physical quantities within a highly dynamic environment, such as a tumbling mill, has been designed, built and tested. To ensure that the instrumented ball is operating as designed, it is made to follow a number of known trajectories. The physical quantities measured by the instrumented ball are consistent with the expected results along the trajectories. An example of the use of a properly functioning instrument is also shown. (C) 2008 Elsevier Ltd. All rights reserved.