Even today, when it comes to comminution of large masses, ball mills are the work horses in the mineral industries. In the past the filling level of ball mills was to be determined by the use of specialized microphone schemes (“electronic ears“), which however showed a series of significant disadvantages (strong interference due to other aggregates in the same hall, low precision, poor reliability) All problems of these “classical“ fill level measurement methods are solved by the new “electronic ear“ produced by KIMA, which uses a different operating principle. A structure borne sound sensor is attached directly on the shell of the rotating mill. It acquires all sounds which occur in the metal wall. Noise and sounds produced by other mills or machines are completely ignored by this sensor, as it is totally insensitive to airborne sound. The signals are transmitted wireless to an industrial PC which analyzes them by means of methods of nonlinear dynamics.

KIMA‘s electronic ear only senses structure borne sound. Thus every type of airborne sound, which is produced by other aggregates does not influence the result of the measurement. Moreover, direct measurement at the mill shell enables the recovery of additional information about the current state of balls, liners and diaphragm Up to three sensors can be connected to one electronic unit (On Mill Unit). Therefore it is possible to measure simultaneously the level of each chamber of two-chamber mills with high resolution and independent of each other. The third input can be used for an additional temperature sensor, which can measure the cement temperature direct in the diaphragm. The On Mill Unit contains its own energy supply, which gains its energy out of the rotation of the mill. This completely avoids regular change of batteries or complex installations (inductive loops or the like).