The maritime sector is working hard to reduce greenhouse gas emissions. Overall, the shipping industry is under considerable pressure to identify innovative solutions, including a transition from conventional to cleaner fuels by 2050.The most promising future fuels are ammonia, ethanol and methanol, which have lower viscosities than current fuels. These new generation fuels are sustainable and have the potential to significantly reduce greenhouse gas emissions.Positive displacement meters are one of the most common types of flow meters used to measure fuel in the marine sector. However, they usually require a certain viscosity to perform properly. The aim of this study is to investigate the measurement performance of a prototype positive displacement fuel consumption meter capable of measuring next generation marine fuels and fuel blends with these and established fuels. The paper outlines the development of the prototype and how it was subsequently improved. Measurements were carried out on the prototype with fuels of different viscosities and line pressures relevant to shipping. The results prove that the meter operates almost independently of viscosity and pressure, making it suitable to accurately measure today's (current fuels), tomorrow's (blended fuels) and future fuels. Finally, suggestions for further improvements are given.

In the future, it may be necessary to assess flow meters with dynamic profiles. It is therefore important to generate dynamic loads in a reproducible manner. At PTB, dynamic flows were realized with cavitation nozzles. Realistic water consumption profiles were generated on a test bench with water. For further use, it is necessary to realize further dynamic profiles and with media other than water. The expansion of the existing infrastructure was successful and dynamic profiles could be generated with cold cleaner. However, the cavitation nozzles could only be used in a non-cavitating state. It turned out that it was not possible to produce dynamic profiles if the internal pipe diameters were too small. It is advantageous if the distance between nozzles and valves is as small as possible. In addition, an expansion vessel only proved to be of limited use for reducing flow peaks during switching processes.

Main text This report presents the results of an inter-laboratory comparison (ILC) organized in order to determine the degrees of equivalence of standards for liquid static flow rates in the range of 50 kg/h to 36 000 kg/h under ambient pressure and temperature conditions. Water was used as the calibration fluid. The objective of the comparison was to support and prove the Calibration and Measurement Capabilities (CMC) in liquid flow of the participating NMIs and DIs CETIAT (France), PTB (Germany), FORCE (Denmark), DTI (Denmark), CMI (Czech Republic), RISE (Sweden), VTT (Finland), BEV (Austria), LEI (Lithuania), SMU (Slovakia) and UME TUBITAK (Turkey). The comparison was organized and evaluated by CETIAT, CMI and PTB as pilot laboratories. The comparison was carried out as a three-loop robin, which started in September 2020 at CETIAT and finished in June 2021, also at CETIAT. Two Coriolis mass flow meters were used as transfer standards. In order to estimate the uncertainties u TS , both transfer meters were subjected to characterization measurements at pilot laboratory CETIAT. The following parameters were researched in detail: fluid temperature, line pressure, reproducibility and the effect of zero setting. Following the results of the Chi 2 -test, one set point of one participant was discarded from the E N calculation. The comparison shows very good agreement between the 11 participating laboratories. Only one laboratory failed the comparison at two set points due to an E N value > 1.2. Two laboratories showed comparison results at "warning level". In order to follow the latest developments in the field of flow comparison evaluation, the standard procedure of COX (2002) was extended by an application of two additional criteria, as for inconclusive or conclusive decisions for calibration. In sum, four laboratories were affected by inconclusive calibration results. The comparison has received financial support from the EMPIR project 17IND13 Metrowamet. To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Reliable fuel consumption measurements play an essential role in the maritime sector whether for emission determinations or the use of novel fuels. A verification of the performance of flow meters used for fuel consumption determination under realistic conditions is thus of interest. Apart from the influence of the pressureand temperature -dependent transport properties of the fuels, a characterization of the measurement performance under dynamic fuel consumption is of relevance. Traceable metrological infrastructure and procedures, which will enable an evaluation of the measurement performance of flow meters in this regard, are being developed in the scope of the EMPIR project "Safest" (20IND13). A consumption profile of a ferry navigating in a harbour serves as basis. In addition to the measurement accuracy under dynamic conditions, first investigations of the performance of flow meters are carried out in terms of fluid temperature and fuel transport properties for the example of spindle screw meters.

Operating and calibration conditions of flow meters vary considerably and have been the subject of various investigations over the years. Based on the knowledge gained and the development of test capabilities that has taken place in the meantime, the investigation of operational influences on the measurement behaviour of the devices can be further advanced. These efforts are driven by stricter requirements on the part of the users of flow measurements, who use these measurements for process optimisation or to prove compliance with given limit values.In the EMPIR project 20IND13 “Safest” infrastructure has been developed enabling a dynamic characterization of flow meters linked to different kinds of flow meter applications. In addition, eventual effects on flow measurements due to changes in ambient and fluid temperatures or deviations between them were investigated. The results for different types of flow meters such as Coriolis and screw spindle meters are presented and discussed.

When testing light-duty and heavy-duty vehicles on chassis dynamometers, as in the WLTP, or engines on engine test benches, as in the WHDC, it is required to measure the fuel consumption. In the preferable case, the measurement of the fuel consumption is carried out with suitable flow meters. These require high measurement accuracy in a wide flow range, independent of the fuel type, as the flow rate range is often very large and depends on the power range of the vehicle engines. Moreover, the fuel flow rate in the test cycles is very dynamically related to the loads. In the scope of the ongoing EMPIR Joint Research Project 20IND13 SAFEST the dynamic flow behaviour as well as the measurement accuracy of flow meters for different types of fuels are investigated. This paper presents first results from the realisation of dynamic flow profiles, and flow measurements with a Coriolis Flow Meter with different representative fuels in a wide density and viscosity range and a wide flow rate range at different fuel temperatures.

The capability to calibrate flow and volume devices dynamically has gained increasing interest over the years. Within the scope of the EMPIR project 17IND13 ‘Metrology for real-world domestic water metering’, several test rigs were developed with which dynamic flow profiles can be generated and measured that reflect characteristics of real-world drinking water consumption. The dynamic component of the test rigs is realized based on different technologies such as valves, cavitation nozzles or piston provers. For validation purposes, an intercomparison of the test rigs was carried out in the scope of an EURAMET pilot study no. 1506. Between September 2020 and February 2021, a transfer standard specially developed for the intercomparison was calibrated at eight laboratories. The measurement error was determined for three dynamic flow profiles representative of drinking water consumption in Europe. In addition to determining the measurement errors and the degree of equivalence, five additional key parameters were derived to characterize the test rig properties: (1) repeatability of the profile measurements, (2) mean value of the residuals, (3) deviation between measured total mass and total mass resulting from the given profile and (4) duration of the flow change for an increasing change (5) and duration of the flow change for a decreasing change. These key parameters comprehensively describe the quality with which the dynamic flow profiles were generated and measured on the test rigs and can be used for evaluations in future intercomparisons of this kind. A main outcome of the intercomparison is that there is no technology to be preferred in terms of technical implementation. All test rigs agree well with each other, taking into account their expanded measurement uncertainties.

The share of electronic water meters installed in households has increased sharply in recent years. However, the current regulations are in large parts still tailored to traditional mechanical water meters. Electronic meters have already been included in the common standards, but reviews and various adaptions are still missing. An important point to be reviewed is the impact of the sampling interval of the electronic water meters on the measurement accuracy of the captured water volume. In this study, the error caused by the sampling interval is investigated by using measured data sets and stochastic water consumption data. It is shown that the error caused by sampling depends on the starting point of the sampling and the observation period. The studies show that for a billing period of one year, which is common in Germany, the sampling interval should be 14 s or less to always ensure a sampling-related error of less than 0.5%. Based on the results, input for further regulations is derived.

Water meters of different types and sizes are used to monitor and bill the water supply. Although the water is of drinking water quality, its chemo-physical properties often enough adversely affect the measuring behaviour of a meter after a while. There is thus the risk that they no longer meet the legal requirements and may no longer be used. In this paper a test regime with a focus on pH, total hardness and particle load is presented which allows water meters to be tested closer to their operating conditions prior to placing them on the market. The regime goes beyond the conventional continuous durability test as described in OIML R49:2013(E) and ISO 4064:2014. The feasibility and reliability of the test regime has been demonstrated through implementation at different facilities. In the study, the measurement performance of water meters of various types and from different manufacturers was also investigated. A heterogeneous spread of measurement errors was found for both, water meters in mint conditions and those which were exposed to a defined water quality. Furthermore, compared to the conventional continuous durability test, the test regime developed in the study generally leads to stronger changes in the measurement error of the water meters.

In the framework of the ongoing EMPIR Joint Research Project (JRP) 17IND13 Metrology for real-world domestic water metering (Metrowamet), a main task is to investigate the influence of realistic operation conditions, that is, typical water qualities (suspended particles, degree of hardness, and pH value), on the measurement accuracy. For this purpose, two representative types of cold water meters were investigated in more detail. Initially, the cold water meters were calibrated and then subjected to an accelerated wear test with water of different pH values and degrees of hardness. The accelerated wear tests were designed to reproduce the realistic use and service life of a cold water meter. Subsequently, the cold water meters were re-calibrated to assess the influence of the different water qualities on the measurement accuracy. One of the results was that the measurement accuracy of the water meters investigated was not strongly affected by the water quality. The practical realisation and the measurement results are reported in this paper.

Today, utility meters for water are tested for measurement behavior at stable operating conditions at specified flow rates as part of the approval process. The measurement error that occurs during start and stop or when changing between flow rates may not be taken into account. In addition, there are new technologies whose measuring behavior under real-world conditions is only known to a limited extend. To take these facts into account, a new method has been developed and tested to determine the measurement behavior of water meters under dynamic load profiles as they occur in the real application. For this purpose, a test rig for flow rate measurement was extended by a cavitation nozzle apparatus and the generation of dynamic load profiles was validated. For the cavitation nozzles used, possible factors influencing the flow rate, such as temperature and purity of the water as well as the upstream pressure were investigated. Using different types of domestic water meters, the applicability of the dynamic test procedure was demonstrated and the measurement behavior of the meters was characterised.

The reduction of water consumption and the technical developments of the last decades, such as the use of tap aerators, water-saving appliances or the use of electronic measuring principles for water consumption measurements at household level, lead to increased and novel demands on flow metering technology. Nowadays, the meters used must be able to detect less water volume with a constant meter size and constantly changing flows. This makes it necessary. to check whether the demanded measurement accuracy is maintained under these changed boundary conditions. Against this background, the question arises to what extent the existing test regimes to assess the measuring performance of water meters are still appropriate. In order to answer this question, it is necessary to set up a metrological infrastructure that will enable water meters to be tested close to real-world operation conditions. Therefore, the following paper focusses on flow dynamics within the water consumption at the household level. One key factor to realize a representative test regime are reliable and representative water consumption measurements at household level. Within the "Metrology for real-world domestic water metering" project (MetroWaMet) within the European Metrology Programme for Innovation and Research (EMPIR) water consumption measurements were carried out in different European countries. Based on the water consumption measurements discussed essential consumption characteristics can be derived in terms of amplitudes and amplitude distributions, gradients or durations. One important outcome of the study is that water consumption in the four different European countries is comparable. This means based on the available consumption data a generally applicable test regime can be derived which can be extended if necessary. The guide developed regarding the planning and carrying out of consumption measurements can be used to collect further reliable and representative consumption data.

ZusammenfassungKavitation ist ein allgemein bekanntes Phänomen in der Welt der Strömungsmechanik. Die Anwendung kavitierender Venturi-Düsen, sog. Kavitationsdüsen als Durchflussregelelement ist hingegen neuartig. Ziel der Untersuchungen zur intermittierenden Durchflusserzeugung durch Kavitationsdüsen ist die Überprüfung der Anwendbarkeit dieser Technologie zur realitätsnahen Prüfung von Durchflussmessgeräten. Die verwendete Apparatur wird in eine bestehende Prüfstandsinfrastruktur integriert. Zunächst werden die Düsen einzeln charakterisiert. Dies belegte eine mit anderen Verfahren bisher nicht erreichte Durchflussstabilität mit einer mittleren Streuung von 0,0015 % der aktuellen Durchflussamplitude. Das Öffnen und Schließen der Düsen innerhalb weniger Millisekunden durch pneumatische Stempel ermöglicht die Realisierung intermittierender Durchflusssequenzen mit einer Wiederholpräzision von bis zu ± 0,07 %. Aufgrund des nahezu additiven Verhaltens der Düsen (± 0,1 %) ist der Volumenstrom von Düsenpaarungen annähernd die Summe der Volumenströme der einzelnen Düsen. Es wurden zwei unterschiedliche Durchflusssequenzen mittels der Kavitationsdüsenapparatur erzeugt und die Reaktion von zwei Durchflussmessgeräten auf den intermittierenden Betrieb beobachtet. Die vorgestellten Untersuchungen belegen, dass der Einsatz von Kavitationsdüsen es ermöglicht, Durchflussmessgeräte unter realitätsnahen Bedingungen mit der erforderlichen Genauigkeit zu testen und zu bewerten - was bisher nicht möglich war. Kavitationsdüsen könnten somit den Weg zu Testverfahren ebnen, die den realen Bedingungen bei Durchflussmessungen am nächsten kommen.

Cavitation is a well-known phenomenon in the world of fluid mechanics. The use of cavitating Venturi nozzles, so-called Cavitation nozzles, as a flow control element is, however, novel. The aim of the investigations on intermittent flow generation by cavitation nozzles is to verify if this technology is applicable for realistic testing of flowmeters. The equipment that was used was integrated into an existing test rig. Firstly, the nozzles are characterized individually. This provided a flow stability of an average scatter of 0.0015 % of the current flow amplitude, which was not achieved with other methods so far. The opening and closing of the nozzles within a few milliseconds by means of pneumatic stamps enables the realization of intermittent flow sequences with a repeatability of up to +/- 0.07 %. Due to the almost additive behavior of the nozzles (+/- 0.1 %), the volume flow of nozzle pairs is approximately the sum of the volume flows of the individual nozzles. Two different flow sequences were created by the cavitation nozzle apparatus and the response of two flowmeters to intermittent operation was observed. The studies presented show that the use of cavitation nozzles makes it possible to test and evaluate flowmeters with the required accuracy under realistic conditions - which previously was not possible. Cavitation nozzles could thus pave the way for test procedures that come closest to real conditions in flow measurements.

The inspection of measurement devices according to statistical sampling plans allows conclusions to be drawn about the reliability of a whole population of devices. However, confirming high reliability levels requires large sample sizes and is thus expensive or even infeasible. For example, a reliability of 99.5% can only be guaranteed with 90% confidence by inspecting each item in a population of 280 (see ISO 2859‐2).

The Geodynamic Observatory Moxa, located in Thuringia/Germany, is dedicated to studies of temporal deformations of the earth's crust and of variations of the gravity field. One of the essential issues with respect to these investigations is the reduction of the hydrological impact on the data of the gravimeters, strainmeters and tiltmeters. In order to optimise the reductions, we investigated the changes in the hydrological conditions in the woody mountain slope above the observatory with time-lapse electrical resistivity tomography (ERT), and analysed the strain and tilt measurements for prominent signatures of pore pressure induced subsurface deformations.Here we present the results for two profiles - parallel and perpendicular to the slope - measured with ERT during 33 campaigns between June 2007 and April 2010. Resistivity changes and variations of apparent soil moisture, inferred from ERT sections, were found to primarily occur in the first two metres of the subsurface. These variations can be related to subsurface flow in the upper two metres induced by precipitation events and snowmelts. Trees close to the profiles only show a minimum impact on the resistivity and soil moisture changes.Furthermore, systematic hydrologically induced deformations can be observed in hodographs of strain and tilt measurements for large precipitation events (>80 mm) and snowmelts. In the strain data a short-term (<3 days) dilatational signal is found with an amplitude of 20 nstrain to 60 nstrain and a long-term (>7 days) compressional signal between 40 nstrain and 180 nstruin. The preferential N-S direction of long-term deformational signals (>1 week) is also observed in the tilt data. The direction of tilt changes (25 nrad-120 nrad) is nearly parallel to the drainage direction of the nearby Silberleite creek indicating variations of pore pressure gradients during hydrological events.The results of these hydrological studies at the Geodynamic Observatory Moxa can be used for removing the time dependent hydrological signal in strain and tilt data and, thus, better correction algorithms for hydrological impacts can be developed to enhance the value of the data for geodynamic studies. (C) 2013 Elsevier B.V. All rights reserved.

The GRACE (Gravity Recovery and Climate Experiment) satellite mission provides global time-series of the Earth's gravity field. In view of limited resolution and noise from the GRACE data, various filtering techniques have been developed to extract an optimal signal. There is no conclusion on the best filter method so far, however. On the other hand, terrestrial gravity observations from superconducting gravimeters (SGs) provide variations of the gravity field with very high accuracy and time resolution, but only at single points. The aim of this study is to compare GRACE-derived temporal gravity variations with gravity time-series within a network of six Central European SG stations. Empirical orthogonal functions (EOF) analysis was applied to detect common signal characteristics over a 3 yr period (2004–2006). rms Differences between the time-series of several GRACE solutions amount to 60 per cent of the rms variability of the individual data sets. The rms differences between the SG and GRACE time-series are about 70 per cent of the rms value of the SG observations. The best agreement between SG and GRACE is obtained when using a Gaussian filter with filter lengths of 800–1250 km for the GRACE data. With the EOF analysis, a common regional signal can be deduced from all gravity data sets. Nevertheless, differences in the first EOF among the GRACE solutions were up to 40 per cent, and differences of up to 50 per cent were found between the SG-based terrestrial and the GRACE-based satellite observations.

Hydrological variations of up to some 10 nm/s2 are significant and broadband signals in temporal gravity observations. On the one hand they need to be eliminated from the data as they interfere with geodynamic signals. On the other hand they can be used to improve the understanding of hydrological process dynamics and to evaluate distributed hydrological models. Compared to satellite observations which are affected by global and regional hydrological variations continuous recordings from superconducting gravimeters (SGs) additionally may contain extractable information on local changes. To compare terrestrial data to satellite observations and to regional/global hydrological models, a local hydrological impact on the observations must be quantified and appropriately reduced first.

The superconducting gravimeter (SG) operating at the South African Geodynamic Observatory Sutherland (SAGOS) is one of the few instruments installed in the southern hemisphere and presently still the only one of its kind on the African continent. SAGOS is located in the Karoo, a semi-arid area with an average annual precipitation of 200–400 mm. The distance to the ocean is approx. 220 km.

Time variable gravity field models derived from the satellite mission GRACE have been demonstrated to be consistent with water mass variations in the global hydrological cycle. Independent observations are provided by terrestrial measurements. In order to achieve a maximum of reliability and information gain, ground-based gravity observations may be deployed for comparison with the gravity field variations derived from the GRACE satellite mission. In this context, the data of the network of superconducting gravimeters (SG) of the 'Global Geodynamics Project' (GGP) are of particular interest. This study is focused on the dense SG network in Central Europe with its long-term gravity observations. It is shown that after the separation and reduction of local hydrological effects in the SG observations especially for subsurface stations, the time-variable gravity signals from GRACE agree well with the terrestrial observations from the SG station cluster.Station stability of the SG sites with respect to vertical deformations was checked by GNSS based observations. Most of the variability can be explained by loading effects due to changes in continental water storage, and, in general, the stability of all stations has been confirmed.From comparisons based on correlation and coherence analyses in combination with the root mean square (RMS) variability of the time series emerges, that the maximum correspondence between the SG and GRACE time series is achieved when filtering the GRACE data with Gaussian filters of about 1000 km filter length, which is in accordance with previous publications.Empirical Orthogonal Functions (EOF) analysis was applied to the gravity time series in order to identify common characteristic spatial and temporal patterns. The high correspondence of the first modes for GRACE and SG data implies that the first EOF mode represents a large-scale (Central European) time-variable gravity signal seen by both the GRACE satellites and the SG cluster. (C) 2011 Elsevier Ltd. All rights reserved.