Digital metrology is now the method of choice in the instrumentation sector with sensing and measurement becoming increasingly dependent on analogue-to-digital conversion of sampled measurements. The scale of digital metrology is already large and is expected to continue to increase. A key benefit is that once the electrical signal has been digitised, quantities such as the basic root mean square (RMS) value, peak value, crest factor and harmonic content can all be calculated from one data set whereas previously, each quantity required a special instrument feature or range and each of these ranges had to be separately calibrated.
The project will bring about a fundamental change to the way in which the volt is disseminated in the SI for AC waveforms. Direct traceability to the quantum standard of voltage, based on the Josephson effect will be provided for sampled electrical measurements. Thus there will no longer be a distinction between so-called DC and AC measurements for the volt and a direct link to the SI for digital measurement systems will be provided at operating frequencies of up to 10 MHz.
The project goes beyond the state of the art in voltage metrology by providing direct traceability over the full range of parameters used to specify analogue to digital converters. Through a coordinated effort by a consortium of 12 European NMIs, the application of the highly successful quantum standard of voltage based on the Josephson effect for DC quantities will be expanded to encompass waveforms as a series of voltage samples and provide a new para-digm for traceability for AC voltages. The aim is to provide direct traceability for precision devices operating at measurement frequencies up to 10 MHz where the measured voltage can be stationary, repetitive or arbitrary depending on need. The traceability will be delivered to the next tier of users using electronic synthesisers specially designed for this purpose in the project, the quantum standards residing in the NMI community where the necessary expertise is invested.
This project will develop fundamental infrastructure that can provide access to the SI for non-stationary voltages via a completely new approach. To achieve this, a quantum-based wave-form standard will be developed in based on Josephson series arrays. Existing calibrators based on electronic devices for dissemination will be adapted. Thus both the accuracy and the range of parameters will be significantly enhanced by this project. In particular, traceability is provided for arbitrary waveforms with known harmonic content. This is not easily available via the existing thermal transfer traceability route.
This project is part of the European Metrology Research Programme (EMRP,
http://www.euramet.org/index.php?id=emrp); it is partly funded by the European Union on the basis of Decision No 912/2009/EC.
