Towards The Resolution Of Discrepancies In The Measurement Of Low Frequency Electrical Conductivity Used For Non-Destructive Testing

摘要

A good example of the need for interoperability of measurement standards exists in the field of electrical conductivity of non-ferrous metals and alloys. This measurement is of particular interest to the aerospace industry and to the coin production and handling industries as it provides a measure of the quality of parts. These industries use commercial conductivity meters which measure the parameter using an AC technique. Traceability to national standards in many countries, including USA, is achieved using DC measurement techniques, although the UK's National Physical Laboratory (NPL) has an established method for achieving this traceability by an AC technique. Due to the effects of frequency and the behaviour of the materials used as reference standards, there can exist discrepancies between the AC and DC techniques. This paper describes a project aimed at addressing these discrepancies being undertaken by a consortium of partners and funded by the European Commission's Framework 5 Programme on Competitive and Sustainable Growth. The partners are 3 national metrology institutes (NPL (UK), PTB (Germany), NMi (Netherlands)), 2 European instrument manufacturers in this area (Hocking NDT Ltd (UK), Institut Dr Foerster (Germany)) and a representative of the aerospace industry (EADS Launch Vehicles).