Reprocessing plants require continuous and integrated safeguards activities by inspectors of the IAEA and Euratom because of their proliferation-sensitivity as complex facilities handling large quantities of direct use nuclear material. In support of both organizations, the JRC has developed a solution monitoring software package (DAI, Data Analysis and Interpretation) which has been implemented in the main commercial European reprocessing plants and which allows enhanced monitoring of nuclear materials in the processed solutions. This tool treats data acquired from different sensor types (e.g. from pressure transducers monitoring the solution levels in tanks). Collected signals are often noisy because of the instrumentation itself and/or because of ambient and operational conditions (e.g. pumps, ventilation systems or electromagnetic interferences) and therefore require filtering. Filtering means reduction of information and has to be applied correctly to avoid misinterpretation of the process steps. This paper describes the study of some filters one of which is the centered moving median which has been revealed as a powerful tool for solution monitoring.