Calibration of commercial conductivity meters for measuring small items

NPL has recently piloted an EC-funded project under the Framework V Competitive and Sustainable Growth Programme on the measurement methods and materials used for electrical conductivity traceability. Electrical conductivity is a quantity used by the aerospace industry for determining the mechanical properties of aircraft sections and components, during production and while in use. During the lifetime of the project it became apparent that the requirements of other industry sectors for traceable conductivity measurements had not been addressed. One area in which conductivity measurements are gaining increased usage is the coin industry for sorting, counting and vending and, through these, as a way of combating fraud. Calibration of these and other processes involves reference artefacts that are themselves calibrated using commercial conductivity meters. It is therefore necessary to know if the coin geometry contributes to the conductivity meter reading.