FIELD: equipment for controlled operation of grinding units. SUBSTANCE: apparatus has transmitter of wave radiation such as ultrasonic or electromagnetic radiation, wave radiation receiver, with transmitter and receiver arrangement allowing radiation to pass through at least inner cavity of ball mill. Wave radiation receiver is connected to electronic circuit generating signal proportional to amount of coal within inner cavity of ball mill on the basis of comparison of received signal to data obtained upon preliminary gage measurements. Wave radiation transmitter and receiver are positioned at both sides of ball mill under control in axial alignment with ball mill shaft so that supersonic radiation is passing axially through inner cavity of ball mill. EFFECT: increased efficiency by improved measurement precision. 9 cl, 4 dwg
