Abstract: A radiation beam that passes through a container but which is severely attenuated or blocked by particulate material within the container is scanned across a container at a desired top layer of particulate material. Radiation emerging from the container during the scanning is detected as to intensity level. Alternatively, a radiation beam is reflected from the material to a detector. The intensity level is sampled at periodic intervals during the scan to determine at periodic positions across the container whether the height of the material therein is above or below the desired fill level. The proportional number of points that are above and below the fill level are compared to a desired threshold for either accepting the container as properly filled or rejecting it as improperly filled.