The problem of detecting the precise amount of bulk material held in a bin is that the surface profile can vary considerably, according to whether the bin has just been loaded or discharged. Single point detectors are therefore only suitable for showing the condition at that point, wall mounted devices being particularly vulnerable to surface contours. Variable height devices detect the level in one axis, but can provide somewhat less uncertainty if suitably located to avoid extremes of repose condition. However, surface scanning equipment is necessary to establish the true stored volume and this can be done by such as equipment as shown on www.info@binmaster.com. The alternative is to mount the bin on load cells for a measure of the amount held. ■