A bin level monitoring system uses one or more monitoring devices (10) to measure a material (23) level in a bin (34). The monitoring devices (10) each have a frame (11) with at least two rigid frame members (12, 13) extending in a longitudinal direction with a space (14) between the frame members. A flexible material (22) covers the frame members (12, 13) and encloses the space (14) there between. A first resistive element (24) and a second resistive or conductive element (30) extend in the longitudinal direction of the device (10) and are arranged to move into contact with each other between the first and second frame members (12, 13) when pressure is applied by bulk material (23) in the bin (34) pressing against an outer surface of the flexible covering (22). An electric circuit (35) connected to the monitoring device (10) measures a total resistance of the free, non-contacted portion of at least one of the first and second elements (24, 30) to provide a measurement of the material level in the bin (34).