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Heft 2: Traceable Dynamic Measurement of Mechanical Quantities

PTB-Mitteilungen 2/2015

Dynamic Measurement of Mechanical Quantities

Foreword by the Editor

The Physikalisch-Technische Bundesanstalt is a player on the most diverse fronts: on the national, the European and the global front. This is only logical – seeing that metrology (PTB’s field of work) is of global concern. For a scientific journal such as the PTB-Mitteilungen, which focuses on topics of metrology, this inevitably calls for internationalization. Precisely this has been taken into account with this issue which has collected scientific papers as the findings of the European research project Traceable Dynamic Measurement of Mechanical Quantities. This project was funded by the EU within the framework of the European Metrology Research Programme (EMRP) and was launched in September 2011. Now, four years later, there is a full spectrum of findings which have been compiled here at one place for the first time.

European Research Project for the Dynamic Measurement of Mechanical Quantities

Michael Kobusch, Thomas Bruns

This first article of this issue of PTB-Mitteilungen presents an overview of the research project IND09 Traceable Dynamic Measurement of Mechanical Quantities, in which a total of nine na tional metrology institutes participated to provide traceability to the dynamic measurement of the three mechanical quantities, force, pressure and torque. The work was focused on developing trace able dynamic calibration methods, mathematical modelling, and evaluation of measurement uncertainty, considering both mechanical sensors as well as the complementary electrical amplifiers. This project began in September 2011 and lasted three years, and was supported by the European Metrology Research Programme of the European Union.

Dynamic Torque Calibration

Leonard Klaus

The demand from industry for dynamic torque calibration has significantly increased over the past years. However, dynamic torque calibrations are not available at present and the respective research activities have started only a few years ago. As part of the European Metrology Research Programme (EMRP), research in dynamic torque calibration took part in work package 3 Dynamic Torque of the joint research project IND09 Traceable Dynamic Measurement of Mechanical Quantities.

Parameter Identification and Measurement Uncertainty for Dynamic Measurement Systems

Sascha Eichstädt

The analysis of dynamic measurements requires new approaches to the estimation of the value of the measurand as well as for the evaluation of measurement uncertainty. In static measurements the value of the measurand is represented by a single value or a tuple of values, and estimation of the measurand typically requires solving algebraic equations. In dynamic measurements the value of the measurand varies with time. In addition, the response of the measurement device depends on the frequency content in the measured time series.

Towards a Shock Tube Method for the Dynamic Calibration of Pressure Sensors

Stephen Downes, Andy Knott, Ian Robinson

In theory shock tubes provide a pressure change with a very fast rise time and calculable amplitude. This pressure step could provide the basis for the calibration of pressure transducers used in highly dynamic applications. However, conventional metal shock tubes can be expensive, unwieldy, and difficult to modify. We describe the development of a 1.4 MPa (maximum pressure) shock tube made from PVC-U pressure tubing which provides a low-cost, light, and easily modifiable basis for establishing a method for determining the dynamic characteristics of pressure sensors.

Measuring Dynamic Pressure by Laser Doppler Vibrometry

Thomas Bruns, Oliver Slanina

The primary calibration of pressure transducers is at present realized by static procedures only. Subsequent dynamic calibrations in this field are realized by comparison measurements with a statically calibrated reference sensor. This paper describes a route to gain traceability for dynamic calibration by means of laser interferometry. As an instantaneous inertia-free measurement, the described procedure has the potential to measure the so far unknown dynamic response of pressure transducers directly with far higher bandwidth than available by the use of a classical reference transducer. This article describes the general principle employed to gain traceability, the experimental set-ups which are used for the realization, some thermophysical and interferometric background of the measurements, and the first measurement results acquired with the new set-up.

Characterization of Force Transducers for Dynamic Measurements

Michael Kobusch

The measurement of time-dependent forces has gained particular importance over the past years. In this context, increasing demands on measurement accuracy have brought new challenges to be solved for the metrological community.

Dynamic force measurements are widely used and play an important role in many industrial areas, for example in the field of material testing, automation and handling engineering, production engineering, vibration tests of mechanical and electronical components for the aerospace industry, and crash tests for safety standards in the automotive industry.

Depending on the specific dynamic application, the nature of the dynamic force differs considerably from case to case. For example, sinusoidal (or periodic) forces are usually applied in fatigue tests, step-like and continuous forces in machining processes, and shock forces in crash tests. A requisite for reliable dynamic measurements is the establishment of an infrastructure for traceable dynamic measurements that is capable of covering such very different load conditions.

Calibration of Bridge-, Charge- and Voltage Amplifiers for Dynamic Measurement Applications

Leonard Klaus, Thomas Bruns and Henrik Volkers

For the dynamic measurement of mechanical quantities, the European research project Traceable Dynamic Measurement of Mechanical Quantities within the framework of the European Metrology Research Programme (EMRP) focused on the development of procedures for traceable measurements of the quantities force, pressure and torque [1–3]. This Joint Research Project (JRP) conjoined experimentalists and mathematicians from nine European National Metrology Institutes (NMIs) for research on the measurands force, pressure and torque. For dynamic measurements of any of these quantities, the respective sensor typically needs to be complemented by a conditioning amplifier. Therefore, these amplifiers were included in the research work as a major component of the traceability chain.

Dynamic Measurements as an Emerging Field in Industrial Metrology

André Schäfer

Since its foundation in the fifties of the last century, i.e. for more than six decades, our company has been serving mechanical engineering as a manufacturer of complete measuring chains from sensor through data processing to software. The first products were amplifiers and inductive transducers. In 1955, the company – as the first company in Europe at all – started the production of strain gauges. This turned out to be a huge success story. Today, strain gauge-based reference transducers and precision instruments are used in the static calibration of quantities such as force, torque and pressure, since this allows the lowest possible measurement uncertainty to be achieved for the measuring chain as a whole. So it is no wonder that in 1977, HBM was the first company ever in Germany to be accredited as an official DKD (German Calibration Service), now DAkkS, calibration laboratory.

Standards and Software to Maximize End-User Uptake of NMI Calibrations of Dynamic Force, Torque and Pressure Sensors: a Follow-Up EMPIR Project to EMRP IND09 “Dynamic”

Sascha Eichstädt, Trevor Esward

The aim of this new project is to maximize uptake by industry end users and the Joint Committee for Guides in Metrology (JCGM) of outputs of EMRP JRP IND09 (Traceable dynamic measurement of mechanical quantities) by providing concrete, specific and directed advice on how to make best use of the results of dynamic calibrations provided by NMIs.

The project’s primary supporter is Rolls-Royce who recognize that dynamic measurements are a key class of problems for high-value manufacturing and are providing data from measurements of unsteady pressure and vibration for the project team to demonstrate the methods developed in EMRP project IND09 in action.

Reference Procedure for the Measurement of Stem Cell Concentrations in Apheresis Products

Jörg Neukammer, Martin Kammel, Jana Höckner, Andreas Kummrow, Andreas Ruf

Reference measurement procedures are indispensable for the reliable determination of blood cell concentrations since medical diagnosis, the initiation of a therapy, and the control of blood products are often based on concentration limits of specific cell subpopulations. We have developed a reference procedure for the direct determination of CD34+ cell concentrations. In the same measurement, the two established routine protocols, i.e. the relative enumeration with respect to calibration particles or to leukocytes, are simultaneously applied.