The mining ore pass is a large bin carved into the rock with a steel frame (grizzly) at the bottom to control feed of the ore into cars for transportation to the top. The walls are uneven and overall distance to the feed frame can be around 225 ft (68 m). Application challenges include the importance of knowing the level measurement as it drops to the area near the feed frame. The level must not go below a minimum level above the frame so that it acts as a buffer from falling rocks and prevents damage to the frame. Also, the ore can be of different grades and sizes and very dusty making level measurement tricky.