Scientific news from division 1

Owing to new procedures, the measurement uncertainty in Doppler Global Velocimetry for the detection of flow velocity fields could be significantly reduced.

The mass of the ²⁸Si sphere AVO28-S8 could be determined in vacuum with a relative standard uncertainty of 6.5 × 10^-9.

The influence of sorption effects on the accuracy of mass determinations under vacuum conditions was significantly reduced by means of sorption artefacts made of a platinum-iridium alloy.

The researchers and university professors who have joined the Forum Braunschweiger Akustiker (FBA) (Braunschweig's Acousticians' Forum) have again retreated for two days at the end of May in the Drübeck Monastery in the Harz Mountains, to extensively discuss, together with their doctoral candidates, their candidates' research topics.

Up to now, for every short duration signal newly developed for audiometry the reference threshold of hearing had to be measured using a group of test persons. By integrating signals into classes, the time and effort for calibration can be reduced.

One of the most important components of the Hydrodynamic Test Field (HTF) – and relevant for its functioning – is the flow diverter. Extensive experimental investigations of the timing error of the corresponding diverting processes and an exact, model-based functional analysis of these processes have greatly contributed to ensuring and quantitatively improving the Hydrodynamic Test Field's...

The petroleum test rig is an integral part of PTB's system of primary standards in the field of volume and flowrate measurement; it works specifically with fluids other than water. The extensions which have been carried out considerably improve the operation of the test rig and now enable us to investigate the transferability of measurement results which have been obtained using the...

It is common practice to use sinusoidal sound signals as an excitation signal to reach the low measurement uncertainties required for the testing of the directional response pattern of sound level meters and for the calibration of measuring microphones. By using broadband signals, it has now become possible to reduce the time needed for a measurement, to considerably increase the spectral...

Aus einem im Rahmen der Entwicklung der Luftlager für die neue 250-kN-Stoßkraft-Kalibriereinrichtung vom Wissenschaftlichen Gerätebau eigens zu Testzwecken angefertigten Luftlager wurde eine neue Kalibriereinrichtung für Impulshämmer aufgebaut.

Die Messung von Kräften und Momenten ist Grundlage zahlreicher Anwendungen in Industrie und Forschung, wie zum Beispiel der Materialprüfung. Ein Problem dabei ist bisher die Kalibrierung von Prüfeinrichtungen wie etwa Werkstoffprüfmaschinen.

Increasingly, Laser Doppler Anemometers (LDA) which are retraced by PTB are used by calibration laboratories, by test benches for air and gas flow rate, and by large test rigs for fluidic and calorimetric flow metering as a transfer standard for the measurement of flow velocity. The primary standard for the calibration of LDA systems – a precisely rotating glass disk – has now been subjected...

Due to the complexity of the problems, measuring and calculating require a solid knowledge base. Persons who already have a professional career often do not find the time to acquire the basics of this specific field in which their profession has "led" them. Thus, many engineers sooner or later discover that they have to do with acoustics without ever having learned it properly.

In many fields of industry – such as for example air-conditioning, environmental technology, meteorology, aviation or wind energy – information about flow velocity is of substantial importance. Measurement devices for detecting the measurand flow velocity, for example vane anemometers, are usually calibrated in wind tunnels.
PTB operates two wind tunnels for the realization and dissemination...

Effect of different protection mechanisms for the pressure transducer diaphragms of piezoelectric sensors on the point pressure during the gas pressure measurement on ammunition for short firearms.

With a calibrated fiber-optic displacement sensor the particle velocity in HITU fields (HITU - High Intensity Therapeutic Ultrasound) was successfully measured. The sensors are highly resistant to strong ultrasound fields and allow measurements of particle velocity with high spatial and temporal resolution.

The Baltic Sea pipeline (Nord Stream) will annually transport about 55 billion cubic meters of gas when it has been completed. It is about 1220 km long, has two parallel pipes, starts in the Russian city of Vyborg and reaches Germany in Lubmin near Greifswald. Germany and the whole of the European Union hope for a more stable gas supply in future and therefore also more energy security...

Wägezellen sind das „Herz” moderner, elektronischer Waagen und können auch als Modul einer Waage separat geprüft werden. In eichfähigen Waagen werden in der Regel nach der internationalen OIML-Empfehlung R60 aus dem Jahr 2000 geprüfte und zertifizierte Wägezellen eingesetzt.

A compilation of many round robin data has revealed that the correlation between one-third octave bands is of major importance for the uncertainty of the A-weighted sound power levels.

Frequently local supermarkets are built within residential areas. Annoying noise is generated as delivery trucks unload their goods. During the planning phase of new supermarkets, the protection of the inhabitants from sound immissions must be proven by numerical predictions. The improvement of these prediction methods has been supported by measurements on a model scale.

An objective hearing test with otoacoustic emissions (OAE) provides information on the inner ear sensory cell performance (cochlear function), even if no cooperation of the subject (e.g. babies) can be expected. OAEs are evoked as a response to an acoustic stimulus and indicate a healthy inner ear. Usually, the stimuli are presented in the ear canal with miniature loudspeakers. An alternative...

Using a modified setup of the radiation force balance, the primary standard for the realization of the unit W in ultrasound, the output power of High Intensity Therapeutic Ultrasound (HITU) transducers could be measured reliably. In the process, a strongly focusing high power transducer was excited with electrical powers up to 500 W.

People walking on different floor coverings are differently loud. As there are countries with regulations about this, the European organisation for standardisation, CEN, awarded a working group the task of developing a corresponding measuring and assessment procedure for walking noise.

The harmonization of European standards initiated in the middle of the eighties of the last century also concerned sound insulation in buildings. The aim of the harmonization was to measure and to evaluate - throughout Europe - building elements and buildings in accordance with uniform standards to facilitate transnational trade and activities.

From September 21 to 24, 2010, the 45th meeting of the International Committee of Legal Metrology (CIML) took place in Orlando, Florida (USA).

In November 2009, a highly regarded two-day seminar on "Technology and procedures of water flow measurement" was organised by the National Institute of Metrology (NIM) of the People's Republic of China, with the participation of PTB. The seminar was very wide ranging as regards contents and - besides questions on measurement uncertainty, traceability, relevant standards and legal regulations...