Process monitoring

Abstract

An apparatus for monitoring a mechanical system comprising a moving surface arranged to undertake periodic motion, the periodic motion having a time period. The apparatus comprises a controller configured to: control a first transducer to emit acoustic waves onto the moving surface during first and second time periods of the periodic motion; receive signals generated by the first transducer or a second transducer, wherein the received signals represent one or both of i) reflections of the acoustic waves from the moving surface and ii) acoustic waves having travelled through the mechanical system; process the received signals to obtain at least one first measurement indicative of a signal received during the first time period, and to obtain at least one second measurement indicative of a signal received during the second time period; compare the at least one first measurement with the at least one second measurement to determine a change of a property of the mechanical system.

Dependencies are inferred from the claim text.