Level indicator for a bulk material hopper - conductive depressions cause sound emitting hammer to rise and fall

摘要

An indicator comprises a motor (1) which drives a paddle (2) through gearing (3). A control circuit (4) comprises a generator (14) which is submitted to a magnetic field by the action of a rotor (10) on two stator windings (11, 12), one of which is connected to the power supply via a capacitor (13) to give a 90 degree phase shift. When the paddle is prevented from turning by the bulk material, amplitude and phase changes are sensed by a rectifier circuit (15) connected to the generator. This activates a relay winding (16) enabling the information to be transmitted. There are typically several indicators at different levels in a hopper, and connected to a common control computer.