| News from the Annual Report 2008 |
• Fundamentals of metrology |
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Measurement of the acceleration of scattering particles in fluids
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For the modelling of turbulent flows, estimating the particle lag and determining the particle size, knowledge of the momentary velocity - including the Lagrangian acceleration - is required. For this purpose, the method of quadrature signal demodulation was used and extended for any type of signals generated by laser Doppler anemometers.
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Detector for the measurement of the kinetic energy of microparticles in space
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In cooperation with partners from industry and from universities, a detector has been developed for the in-situ measurement of the kinetic energy of impacting, fast microparticles. An array composed of sensible microcalorimeters measures the heating of the absorber caused by the particle impact. The novel measuring principle offers - compared to the detectors so far used - considerably smaller measurement uncertainties and a higher reliability.
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Investigations into damping in building acoustics by use of downscaled models
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In the frame of a doctoral thesis basic investigations into damping effects in the field of building acoustics have been carried out. Special interest is paid to the damping of a partition wall in a laboratory test facility. This damping directly affects sound insulation which is the most important quantity in building acoustics.
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Radiation force calculations for ultrasonic fields from rectangular transducers
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The radiation force formula for ultrasonic fields produced by rectangular transducers has been calculated in order to improve the reliability of the ultrasonic power measurement by means of a radiation force balance with particular respect to those field types.
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Increased accuracy of air density determination for buoyancy correction in precision mass determinations
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The use of buoyancy artefacts and more accurate calculation bases for air density determination made it possible to significantly reduce the uncertainty of the air buoyancy correction in precision mass determinations.
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Improvement of the realization of forces between 2 MN and 5 MN
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In the past, PTB only had the 16.5 MN force standard machine (FSM) at its disposal for the investigation of force transducers with measurement ranges larger than 2 MN. Due to the great demand for calibrations in this upper force range, this caused, time and again, bottlenecks as this machine for forces in tension and forces in compression, which is worldwide unique due to its size and accuracy, was not always able to satisfy the great demand for measurements applied for. Among the great number of orders, the share of transducers up to 5 MN amounted to approx. 80%.
For this reason, PTB has decided to make use of a hydraulic force standard machine taken over from the former ASMW (Amt für Standardisierung, Messwesen und Warenprüfung of the GDR - Office for Standardization, Metrology and Commodities Testing) and to utilize it - after its complete modernization as force standard machine - for forces up to 5 MN. It was aimed at reducing the uncertainty in the force realization of this machine to 0.01%. At the same time, the updated facility shall allow an efficient, automated operation. New concepts for the cascade control and for the method used to link up the machine with the standards have been investigated and realized. - more ...
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| • Metrology for economy |
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A calibration procedure for a force vector sensor by means of a spherical calibration body
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Force standard machines generate a force vector whose direction is determined by the acceleration due to gravity. For the calibration of force vector sensors, different alignments of force vectors - in relation to the coordinate system of the force vector sensor - are required. For that purpose, a special calibration body has been developed. From the signals of the measuring channels of the sensor and from the force vector, a transmission matrix was calculated which provides information about the signals of the single components and which indicates cross-talk of the channels.
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Development and investigation of force transducers with thin-film strain gauges
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Within the scope of a DFG research project at PTB, metal thin-film strain gauges were sputtered on force transducers, and their behaviour was investigated. In some fields of force measurement, the use of thin-film strain gauges promises advantages compared to the usually used foil strain gauges.
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Novel dynamic measuring methods for industry
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In August 2008, the project "Model-based calibration of accelerometers" which is supported by the Federal Ministry of Economics and Technology (BMWi), was completed successfully. The objective was to transfer to industry novel measuring procedures and methods of data analysis for the calibration of accelerometers as have been developed at PTB over the last few years.
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Investigations on Silicon Load Cells with Thin-Film Strain Gauges
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Load cells (LCs) with single-crystal mechanical springs (MSs) and sputtered-on strain gauge (SGs), due to the ideal elastic properties of the MSs, promise a low time-dependent behaviour and a high reproducibility of the measuring signals. These sensors would thus be optimally suited for use in mechatronic systems in order to digitally compensate for further influence factors such as temperature dependences and non-linearities. Investigations carried out on an MS made of silicon (Si) have confirmed the - by a factor of 100 lower - time-dependent behaviour compared to metallic MS. Presently, Si LCs are being investigated as to their linearity, hysteresis and the reproducibility of the measuring signals. First comparative measurements on metallic and Si load cells have confirmed the better properties of the Si LCs.
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| • Metrology for society |
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Test facility for temperature effects on the measuring behaviour of gas meters
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A new test equipment for gas meters with temperature control of the test air between -40 °C and +80 °C was put into operation in 2008, and first serial examinations of laminar flow elements have been successfully carried out as part of a degree dissertation.
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Uncertainty of predictions in building acoustics
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A new approach for calculating the measurement uncertainty made it possible for the first time to realistically evaluate the uncertainties of building acoustic predictions according to EN 12354-1 from the uncertainty contributions of the acoustic input quantities. It is expected that this leads to a significantly improved acceptance of such demonstrations being important for the noise protection in buildings.
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PTB supports development of effective sound insulation for orchestra musicians
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EU Directive 2003/10/EC defines increased requirements for the protection of employees against noise hazards. The practical realization, which has Europe-wide been demanded until February 15, 2008, represents a serious problem, especially for the musicians of a symphony orchestra.
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Six semesters of building acoustics in three days
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People who are pursuing a professional career do not often find the time to acquire the basics of a specialist area to which their career path may have led them. Many engineers thus discover at some point that they have to deal with acoustics without ever having studied this area properly. The Academic Programmes of the Deutsche Gesellschaft für Akustik (German Acoustical Society) fill these gaps. These Academic Programmes - in short but intensive courses on specialist areas of acoustics - aim at instructing people who do not have enough time in their everyday working lives.
One such programme took place at the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig in June, focussing on "Building Acoustics".
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Hearing thresholds for new short-duration signals: The equality of hearing thresholds for click and chirp signals is shown
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Click and chirp signals with identical amplitude spectra have equal behavioural hearing thresholds for audiometric routine. This might simplify calibration procedures.
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Temperature conversion of ethanol-gasoline mixtures
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In order to enable legally required temperature conversion also for bio fuels and mixtures of bio fuels with conventional fuels PTB carried out first investigations of the temperature-density behaviour of these liquids.
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| • International affairs |
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Successful completion of the first worldwide torque comparison
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The international comparison ("key comparison") CCM.T-K1 which was started in 2005 for torques of 500 N·m and 1 kN·m was completed after the report had been agreed upon by the participants. Thereby, at best, the expanded (k = 2) measurement uncertainties of 2·10-5 stated by the partners could be confirmed, which also shows that the realization of static torques with smallest measurement uncertainties is mastered.
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Start of a new cycle of the European Harmonised Cubic Metre for high-pressure natural gas
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After the routine recalibration of all the test rigs involved (from France, Germany and the Netherlands), a new cycle for the maintenance of the European Harmonised Cubic Metre for high-pressure natural gas has been launched successfully.
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Comparison calibration of a heavy tri-axial velocity transducer
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The specified quality of a vibration exciter may be strongly affected by parasitic transverse motions occurring as a result of the load exerted by the object to be calibrated. Mass, size, stiffness and mechanical coupling of the sensor have an influence on the quality of the desired - usually uniaxial - vibration motion. Following a request of METAS (Switzerland), a rather large and heavy tri-axial velocity transducer for their local calibration device was calibrated on PTB's multi-component vibration exciter which is designed for higher loads. By laserinterferometric determination of the reference and interference quantities it could be shown that the influence of parasitic rotational motions can, to a large extent, be compensated computationally.
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New WELMEC-Guide for automatic weighing instruments (AWI) adopted
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For several decades now, electronic weighing instruments have been tested and approved for verification at first as nonautomatic weighing instruments (NAWI), while subsequently the approval as automatic weighing instruments (AWI) is being applied for. In the past it became obvious that European notified bodies partly followed different philosophies when handling such applications. It was alarming that the specific metrological problems of AWIs had partly not been taken into account at all.
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News from past Annual Reports
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2007 |
2006 |
2005 |
2004 |
2003 |
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