In this paper, a development of the shock tube at RISE, the National Metrology Institute of Sweden, to extend its capability to the high-pressure regime is presented. The shock tube was developed to be operated in three different configurations: conventional, with an amplification system and with a converging cone. In the conventional and with the amplification system, the well-established shock tube analytical solution was used to calculate the reference pressure, while in the converging cone, a numerical simulation was applied. To demonstrate the capabilities and limitations of each configuration, a device under test (DUT) was characterized. The results show a good agreement in the DUT dynamic response calculated using the three configurations in the overlap regions between them. The uncertainty in measurements was estimated for each configuration. The three configurations complement each other to reach a pressure range from 0.1 MPa to 25 MPa and a frequency range from 0.5 kHz to 500 kHz.

A secondary measurement standard filling the gap between the available static and dynamic standards was developed. The standard utilizes a quick-opening valve and bursting diaphragms to generate step-like pressures with amplitude of few kilopascals to 10 MPa and with frequency content from 10-2 Hz to 800 Hz. An important design feature of the developed standard lies in the usage of aluminium diaphragms, allowing short rise times and high frequency content. The standard is based on two reference sensors, calibrated statically and dynamically. The reference sensors showed a linear dynamic response in the intermediate frequency range and was in good agreement with the static calibration results. Therefore, extrapolation of shock tube results was implemented. To demonstrate the capabilities of the developed standard, three pressure measurement systems were characterized, and their respective dynamic response was calculated. The results show that the developed standard can provide calibration information that are not currently available.

Methods and technologies for dynamic measurements have been developed and used for decades. To enable robust metrological traceability, uncertainty analysis methods for various applications have been derived and published by many scientists. In Europe, several research projects funded within European metrology research programmes (EMRP, EMPIR, Partnership on Metrology) have been focusing in dynamic measurements of mechanical, thermal and electrical quantities to provide new measurement and calibration methods. The European Metrology Network “Mathmet” drives the development of analytical methods related to dynamic measurement applications. The importance of dynamic measurement solutions has been boosted by digitalisation and rapid growth of computer power. Artificial intelligence combined with sensor fusion and sensor networks brings dynamism to wider measurement applications but may hide serious vulnerabilities to time dependent disturbances. At the moment most calibrations are performed under static conditions, i.e. the time dependency of the measurand is considered as a very small contribution to the overall calibration uncertainty. Calibrations at static conditions are often preferred due to practical reasons even if dynamic calibrations are available. In its recent strategy, the European Metrology Network “Smart North” has identified dynamic measurements as a field of regional competence and service development within Nordic and Baltic countries. This paper reviews most relevant research results and currently available calibration services in Europe. The study is focused on measurement needs related to machinery, combustion engines and electrical grids. Potential future needs for NMI level services in the region are analysed by considering specific needs of local industry, societal resilience and northern climate.

The design, performance characteristics and validation of a next generation reference facility for carbon dioxide (CO2) in air standards based on manometry is presented. Novel attributes of the facility include automated operation, avoidance of significant pressure corrections for measurements on extracted CO2, fully characterized trapping efficiencies, and reduced measurement uncertainty. Improvements in system performance have been achieved using specific materials, notably Silconert®-treated stainless-steel, providing increased mechanical stability whilst minimizing carbon dioxide adsorption on surfaces, and avoiding use of elastomer O-rings, which would lead to losses of CO2. Full automation of the cryogenic extraction process of CO2 from air has been achieved, avoiding any manual intervention within the temperature stabilized section of the facility, and allowed full characterization and correction for trapping efficiencies and trace water measurement. The facility has been validated across the CO2 in air amount fraction range of (380-800) µmol mol−1 using standards with values traceable to the reference value of the CCQM−K120 (2018) comparison. It was demonstrated to operate with a standard measurement uncertainty of 0.09 µmol mol−1 at 400 µmol mol−1. The automation allows five measurement results per day to be produced with a typical standard deviation of the mean at or below 0.02 µmol mol−1. The facility will be used as a stable reference in the future BIPM.QM−K2 ongoing comparison, to compare consistency of amount fraction values in different CO2 in air standards. The CO2 amount fraction in two ensembles of nine BIPM standards covering the same range will also be measured with the facility to provide their SI-traceable values, and further monitored on a longer time scale. Each ensemble will constitute a CO2 in air scale to be compared with other available scales such as WMO.CO2.X2019 through the BIPM.QM−K5 comparison.

The extremely rapid reflection of a shock wave from the end wall generated in the shock tube, in addition to the high-frequency content of pressure, inevitably also excites mechanical vibrations. These can potentially produce acceleration-induced spurious signals as part of the dynamic output of the pressure measurement system being calibrated. This paper proposes and evaluates a method for correcting the frequency response of a pressure measurement system obtained with a calibration using a shock tube for the acceleration-induced errors due to vibrations. The proposed method is based on the predetermined frequency response of the pressure measurement system to the accelerations and simultaneous measurements of the vibration accelerations of the pressure sensor during its calibration in the shock tube. The acceleration-induced errors were corrected for a piezoelectric pressure measurement system calibrated in a diaphragmless shock tube developed at the National laboratory for pressure and vacuum at RISE Research Institutes of Sweden, where different vibrational conditions were induced by changing the initial driver pressure, while keeping the initial driven pressure constant. The uncertainty of the correction of the frequency response of the piezoelectric pressure measurement system being calibrated was determined by considering the uncertainty contributions of the measured acceleration frequency response of the pressure measurement system, the measured acceleration of the pressure sensor during its calibration in the shock tube, the generated reference end-wall step pressure and the repeatability of the correction. The results show that the proposed method effectively eliminates acceleration-induced errors in the sensitivity and phase frequency responses of an acceleration-sensitive piezoelectric pressure measurement system being calibrated with a shock tube.

In this paper, we introduce a robust method for dynamic characterization of pressure measuring systems used in time-varying pressure applications. The dynamic response of the pressure measuring systems in terms of sensitivity and phase as a function of frequency at various amplitudes of the measurand can be provided. The shock tube which is the candidate primary standard for dynamic pressure calibration at the National Laboratory for pressure, Sweden, was used to realize the dynamic pressure. The shock tube setup used in this study can realize reference pressure with amplitudes up to 1.7 MPa in the frequency range from below a kilohertz up to a megahertz. The amplitude of the realized step pressure was calculated using the Rankine–Hugoniot step relations. In addition, the accurate time of arrival of the generated shock at the device under test (DUT) was measured using an optical probe based on shadowgraphy. The optical detector has a response time in nanosecond time scale which is several orders of magnitude faster than the response time of any pressure measuring system. Hereby, the latency between physical stimuli and response of the DUT can be measured. By the knowledge of the amplitude and the accurate time of arrival of the reference step pressure, the transfer function of the DUT can be calculated and presented in Bode diagrams of sensitivity and phase response versus frequency. The uncertainty in sensitivity and phase measurements was estimated. The information provided by this work is useful for developing reliable models of dynamic pressure measuring system and provide accurate information about their dynamic response. That in turn will contribute to establish a traceability chain for dynamic pressure calibration.

Accurate dynamic pressure measurements are increasingly important. While traceability is lacking, several National Metrology Institutes (NMIs) and calibration laboratories are currently establishing calibration capacities. Shock tubes generating pressure steps with rise times below 1 µs are highly suitable as standards for dynamic pressures in gas. In this work, we present the results from applying a fast-opening valve (FOV) to a shock tube designed for dynamic pressure measurements. We compare the performance of the shock tube when operated with conventional single and double diaphragms and when operated using an FOV. Different aspects are addressed: shock-wave formation, repeatability in amplitude of the realized pressure steps, the assessment of the required driver pressure for realizing nominal pressure steps, and economy. The results show that using the FOV has many advantages compared to the diaphragm: better repeatability, eight times faster to operate, and enables automation of the test sequences.

A EURAMET key comparison of the national pressure standards in the range 0.7 MPa to 7.0 MPa of gas gauge pressure was carried out. The circulation of the transfer standard began in November 2011 and lasted until November 2016. The measurand of the comparison was the effective area of the piston-cylinder assembly determined by gauge pressure measurements in the range from 0.7 MPa to 7.0 MPa. As the comparison reference value, the weighted mean of the results of the laboratories with primary pressure standards was used. With this reference value, all the participants who delivered the results demonstrated equivalence respective to the reference value within expanded uncertainties (k = 2) on all the range. The results of this comparison were linked to CCM key comparison CCM.P-K1.c. Also in relation to the reference values of CCM.P-K1.c, all participants demonstrated agreement within expanded uncertainties (k = 2) at all pressure points.

This project has five specific objectives: To provide traceability for dynamic pressure and temperature through development of measurement standards and validated calibration procedures; To quantify the effects of influencing quantities on the response of dynamic pressure and temperature sensors, in order to determine the appropriate calibration procedures and measurement uncertainties for industrial measurements; To develop new measurement methods and sensors for measuring dynamic pressure and temperature in demanding industrial applications, and to demonstrate the improved accuracy and reliability obtained with those; To validate all of the methods and sensors developed in this project through demonstrations in selected industrial applications; and To ensure by close engagement with industry, that the developed calibration and measurement techniques and technology are adopted by them. The challenge is that in many industrial applications pressure and temperature measurements are performed under dynamically changing conditions. The aim of this project is to improve the accuracy and reliability of pressure and temperature measurements in these challenging conditions. A European joint research project named Development of measurement and calibration techniques for dynamic pressures and temperatures (shortname DynPT) started in the summer 2018.

Measurements of mechanical quantities such as pressure often take place under dynamic conditions, yet no traceable standards for the primary dynamic calibration of pressure sensors currently exist. In theory, shock tubes can provide a close to perfect step-function ideal for the calibration of pressure transducers. In this paper we investigate a system consisting of a shock tube and an ultra-fast fiber-optical sensor that is designed to be a future primary system for dynamic pressure calibrations. For reference, the fiber-optical sensor is compared to a piezoelectric sensor, and their corresponding frequency spectra are calculated. Furthermore, an investigation of the repeatability of the fiber-optical sensor, as well as a comparison with a second shock tube, is performed.