Measurement: Sensors (Dec 2021)
Progress in the realisation of ultra- low frequency vibration calibrations
Abstract
The demand from industry to produce high credibility measurement data down to ever lower frequencies with ever lower noise is increasing. Recently also a demand to support the operation of global networks for environmental monitoring and research in areas such as climate change and non-proliferation of nuclear weapons has evolved. The EUROPEAN METROLOGY PROGRAMME FOR INNOVATION AND RESEARCH (EMPIR) has initiated several projects to support this area. This project 19ENV03 Infra-AUV has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. Several national metrology institutes including the DPLA are participating.The expected resulting calibration capability will bring much needed key metrology concepts, such as traceability and measurement uncertainty, into focus in these applications for the first time.Vibration transducers for such purposes must be calibrated to yield trustworthy results and provide traceability to SI-system accordingly. For these calibrations to be feasible, suitable ultra low noise accelerometers and signal analysis are needed.High sensitivity piezoelectric accelerometers with integrated electronics have normally not been considered feasible for these purposes due to the low frequency limit imposed by the internal and external electronics.In this paper we present some considerations found relevant when preparing laboratory premises for low frequency and ultra-low frequency calibration in general along with recent results from the DPLA system built on a high-performance analysis system realising the ISO 16063-11 Method 3.We also present some preliminary results of analysis based on real signals from two accelerometers using the coherent power (COP) and argument (COA) method (COPA) as described in an earlier paper [1].
