By combining imaging technology with liner wear-monitoring hardware, the Sentinel system reveals live information from within a mill without the need to pull the feed chute or have personnel enter inside.  Viewing and recording live imagery of a running mill, measuring the wear of a liner, assessing the internal conditions, and checking or setting the charge level, are all now possible in real time without the need to isolate any plant or equipment.  Access to this information presents new opportunities for improving operational metrics, reducing running costs, and provides a detailed empirical basis for liner-life prediction and maintenance planning.