Changes to the UK electrical reference standards

The accuracy with which electrical measurements can be made depends upon the accuracy with which national laboratories can realise and maintain their representations of the ampere, volt and ohm. Changes in the national reference standards for the volt and ohm which will be implemented on 1 January 1990, are discussed. It is pointed out that reference standards based on the Josephson and quantised Hall effects achieve fixed results and that their accuracy is limited by the accuracy of the present generation of primary standards