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Here we have selected a few of the photos from PTB which are often requested. You can download them – in print quality and with captions.

You may download and publish the photos in our photo gallery free of charge for editorial and purely private use – but not for commercial use. Please note the source information, which is stated next to the image caption in each case. And, after publication, please send us a copy of your document or a link to it.

SI Base Units

MetreMetre

  • The "prototype of the meter" (1.6 MB) Today, the "prototype of the meter" is a museum piece. It is kept secure in a safe at the International Bureau of Weights and Measures (BIPM) in Sèvres near Paris. From 1889 to 1960, it was the official embodiment of the SI base unit "meter". Described a little more formally, it was the international prototype of the meter, a line gauge with X-shaped cross-sectional profile made of platinum-iridium. (Photo: PTB)
  • The Braunschweig cubit (8.6 MB) Until the French Revolution, every sovereign had their own cubit – and this brought about massive trading problems for their subjects at no extra charge. The Braunschweig cubit is 57.07 cm long and can still be seen today as it is set in the wall of the Old Town Hall of the city. (Photo: PTB)
  • Krypton standard lamp (2.6 MB) With the krypton standard lamp it became possible for the first time to couple the unit of length to an atomic constant and to reproduce it at any place on Earth without a loss of accuracy. From 1960 to 1983, the krypton standard lamp served to realize the unit of length. (Photo: PTB)
  • Emission of iodine molecules in the red and green spectral range (4.1 kB) Particularly stable lasers make it possible that a wavelength once measured – and, thus, the unit of length – can be maintained in laser wavelength standards/frequency standards. PTB keeps different laser wavelength standards in the infrared, red and green spectral range at its disposal. The photo shows the emission of iodine molecules in the red and green spectral range. (Photo: PTB)
  • A laser wavelength standard (2.0 MB) This is how the unit "meter" is realized today at PTB: A laser wavelength standard with a stabilized, frequency-doubled neodymium:YAG laser (yttrium-aluminum-garnet laser) provides light of an accurate frequency for interferometric length measurements. (Photo: PTB)
  • Frequency comb (467 kB) Frequency combs connect the world of the meter with the world of the second. They quasi serve as a "gear" which allows frequencies to be "transmitted" without any loss of accuracy. In contrast to the frequency synthesis chains used in the past, they allow any laser frequency desired to be measured. They are, for example, used to compare optical frequencies with primary clocks or for the direct comparison of two optical frequencies. The image shows the spectrally expanded frequency comb spectrum of a titan-sapphire laser. (Photo: PTB)
  • HeNe-laser stabilized by absorption in iodine (2.6 MB) HeNe-laser stabilized by absorption in iodine at PTB for the calibration of laser wavelength standards. (Photo: PTB)
  • Calibration of a reference mask (2.3 MB) PTB calibrates reference masks; with its nanometer comparator, it measures them accurately to a few nanometers. The photomask is carefully removed from its packaging. Here, the following applies everywhere: Maximum precision and care. Photomasks are the most expensive material which is required for the manufacture of microchips. They carry a precise image of the circuits and are the master whose pattern is exposed during chip production and transferred onto the silicon wafers. These patterns are unimaginably tiny: One chip of the size of a fingernail accommodates more than one million switching elements. (Photo: PTB/original-okerland).
  • Interior of the nanometer comparator at PTB (1.2 MB) Interior of the nanometer comparator at PTB: Directed by mirrors, the laser beam makes its precise way, is split, united again – and can finally measure a length accurately to the nanometer. (Photo: PTB/original-okerland)
  • Gauge blocks (1.3 MB) Fascinating adhesive force: Gauge blocks stick together without any adhesive, only by atomic forces. They allow lengths to be "manufactured" accurately to one micrometer which should then, if possible, also be indicated by a length measuring instrument. (Photo: PTB)
  • A set of gauge blocks (3.1 MB) The most exact building bricks that can be found: A set of gauge blocks, consisting of 122 pieces for calibrations in industry. (Photo: PTB) Or: Gauge blocks are the most accurate and most simple material measures of length which are used to disseminate the unit of length, the meter, to industry. They have a rectangular shape and consist of wear-proof material, e.g. steel, tungsten carbide or ceramics. Gauge blocks of specially graded lengths are combined to gauge block sets so that every length in a range from 2 mm to 200 mm can be realized in steps of 1 µm by combining just a few gauge blocks. (Photo: PTB)
  • Two gauge blocks (2.8 MB) At PTB, the thickness of such gauge blocks is determined accurately to fractions of a thousandths of a millimeter with the aid of interferometric methods (Photo: PTB) Or: The gauge block reference surfaces can be manufactured with high accuracy in a plane, parallel form and with a very fine finish. The optical properties associated with it allow the unit of length, the meter, to be transferred to a gauge block in a direct measurement procedure in accordance with the measurement principle of light interference. (Photo: PTB)

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KilogramKilogram

  • The international prototype of the kilogram (2.0 MB) The international prototype of the kilogram, kept under three bell jars at the International Bureau of Weights and Measures (BIPM) in Sèvres near Paris. (Photo: PTB/BIPM)
  • The international prototype of the kilogram (2.8 MB) The international prototype of the kilogram, kept under three bell jars at the International Bureau of Weights and Measures (BIPM) in Sèvres near Paris. (Photo: PTB/BIPM)
  • The national prototype of the kilogram at PTB (587 kB) In Germany, it is the "measure of all measures": The national prototype of the kilogram (No. 52) at PTB, one of the copies of the international prototype of the kilogram. (Photo: PTB)
  • View into a prototype balance of PT (1.0 MB) View into a prototype balance of PTB with the aid of which 1-kg mass standards can be linked up with the national prototype of the kilogram. The balance shown is a 1-kg vacuum-mass comparator, installed in a vacuum-proof chamber (photo: PTB)
  • Weights (0.9 MB) Weights. At PTB, the masses of standards are derived from the national prototype of the kilogram in the large span from 1 mg up to 5 t. This is how the mass scale is realized. (Photo: PTB)
  • Arnold Nicolaus with one of the "kilogram spheres" of PTB (2.5 MB) The work of Arnold Nicolaus is completely concentrated on the sphere. To find out how many atoms are contained in the crystal lattice of the silicon sphere, Nicolaus must first determine the volume of the sphere. Perfect spheres exist, however, only in mathematics. Therefore, it is not sufficient to measure the diameter once and to enter it into the volume equation for a sphere. What is needed is rather the exact topography. After thousands of measurements it is clear: Although it is not a sphere, it is a very good approximation. (Photo: PTB/original-okerland)
  • The silicon sphere in PTB's spere interferometer (2.5 MB) The sphere made of a particularly isotopically pure silicon single crystal is measured exactly to the nanometer in PTB's sphere interferometer. (Photo: PTB/original-okerland)
  • One of the silicon spheres of the Avogadro project at PTB (1.6 MB) Very complex manufacturing: One of the silicon spheres of the Avogadro project at PTB. (Photo: PTB)
  • Spheres made of almost monoisotopic 28Si (1.7 MB) Spheres made of almost monoisotopic 28Si are used to measure the Avogadro constant which is required for the redefinition of the International System of Units (SI). (Photo: PTB)
  • Avogadro sphere at PTB (1.5 MB) One of the silicon spheres of the Avogadro project at PTB. (Photo: PTB)
  • The sphere interferometer of PTB (2.7 MB) Metrological research (in most cases) requires perseverance. The Avogadro project for the redefinition of the kilogram and the mole has spanned more than two decades. The photo shows the sphere interferometer of PTB with the aid of which the diameter of the silicon spheres of the project, which have been manufactured with great effort, can be measured accurately to a few nanometers. (Photo: PTB)Within the scope of the Avogadro project, mass spectrometry is also applied to exactly determine the ratio of the different silicon isotopes. (Photo: PTB)
  • PTB's sphere interferometer (0.9 MB) PTB's sphere interferometer allows complete diameter topographies to be determined with extreme accuracy. It is one of the decisive measuring devices within the scope of PTB's Avogadro project. In 1996, it was, for the first time, installed by Gerhard Bönsch and Arnold Nicolaus as a fundamentally new optical multi-beam interferometer with spherical reference faces. (Photo: PTB)
  • Diameter variations on a silicon sphere (316 kB) Diameter variations on a silicon sphere measured with the sphere interferometer within the scope of the Avogadro project. The color variation from blue to red visualizes deviations from the perfect spherical form of approx. 20 nm. The volume is calculated from a great number of diameter measurements. (Photo: PTB)
  • Silicon single crystal (1.1 MB) From such silicon single crystals, a sphere for the Avogadro project is manufactured with great effort (photo: PTB). This single crystal consists to more than 99 % of the isotope silicon-28. (Photo: PTB)
  • PTB's mass spectrometer (1.3 MB) PTB's mass spectrometer which is used to determine the ratio of the different silicon isotopes. (Abb.: PTB)

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SecondSecond

  • PTB's primary atomic clock CS2 (1.3 MB) PTB's primary atomic clock CS2 furnishes the second intervals of legal time (CET and CEST) with the aid of which all radio-controlled clocks in Germany are controlled via a long-wave transmitter in Mainflingen near Frankfurt. (Photo: PTB)
  • Aluminium clock (1.0 MB) One single aluminum ion in a trap is to ensure that time can, in future, be measured with an accuracy which is a hundred times greater than today. Piet Schmidt from the QUEST Institute at PTB wants to construct the most accurate clock in the world. (Photo: PTB/original-okerland)
  • Piet Schmidt with the optical aluminium clock (874 kB) Piet Schmidt from the QUEST Institute at PTB is adjusting the optical aluminum clock which could one day become the most accurate clock in the world. (Photo: PTB/original-okerland)
  • Coding scheme of the time signals emitted by DCF77 (118 kB) Coding scheme of the time signals emitted by DCF77; M: minute mark, R: bit reserved for internal use; A1: announcement bit of an imminent change from CET to CEST or vice versa, Z1 (Z2): announcement of a leap second, S: start bit of the encoded time information (0.2 s), P1, P2, P3: parity check bits. (Photo: PTB)
  • The two cesium fountains CSF1 and CSF2 (1.7 MB) Prominent showpieces of PTB: the atomic clocks (here: the two fountain clocks). No other physical quantity can be measured as precisely as time. (Photo: PTB). The two cesium fountains CSF1 and CSF2 (with Dr. Stefan Weyers, Head of the "Time Standards" Working Group) (Photo: PTB)
  • The ion trap of the ytterbium clock (811 kB) The ion trap of the ytterbium clock at PTB. (Fig.: PTB)
  • PTB scientist Ekkehard Peik with the ytterbium clock (1.0 MB) PTB scientist Ekkehard Peik with the ytterbium clock. (Photo: PTB/original-okerland)
  • PTB's optical strontium clock (1.6 MB) PTB's optical atomic clock which works with stored strontium atoms. (Photo: PTB)
  • View of the ultra-high vacuum chamber of PTB's optical strontium clock (829 kB) View of the ultra-high vacuum chamber where strontium atoms are cooled and stored. The blue fluorescent light in the upper third of the window is a cloud of cold strontium atoms (the drop-shaped formation below the blue fluorescent atom beam in the upper part of the vacuum window). (Fig.: PTB)
  • Blick in die Vakuumkamer der optischen Sr-Gitteruhr (3.0 MB) Blick in die Vakuumkamer der optischen Sr-Gitteruhr, in der die Strontiumatome gefangen und abgefragt werden, mit der im oberen Teil erkennbaren blau fluoreszierenden Atomwolke mit einer Temperatur von wenigen Millikelvin. (Abb.: PTB)Oder:Blick in die Ultrahochvakuumkammer, in der die Strontiumatome gekühlt und gespeichert werden. Darin ist der Plattenkondensator zu sehen, vor dem blau eine Wolke von einigen Millionen Strontiumatomen fluoresziert. Vor der Anregung des Überganges werden die Atome in den Kondensator transportiert. (Abb.: PTB)
  • The ytterbium clock of PTB (775 kB) The ytterbium clock of PTB. To be more exact: Vacuum recipient with ion trap (in the center) for the spectroscopy of single ytterbium ions. (Photo: PTB/original-okerland)
  • Ion trap of the optical ytterbium clock at PTB (1.0 MB) The faster a clock ticks, the more precise it can be. Due to the fact that light waves vibrate faster than microwaves, optical clocks can be more precise than the cesium atomic clocks which currently determine time worldwide. The Physikalisch-Technische Bundesanstalt (PTB) is even working on several such optical clocks. One of it works with a single ytterbium ion trapped in an ion trap. (Photo: PTB/original-okerland)
  • Fluorescence of a cloud of calcium atom (715 kB) Fluorescence of a cloud of calcium atoms during the first phase of laser cooling in PTB's optical calcium clock (Photo: PTB)
  • PTB's primary atomic clock CS2 (1.2 MB) PTB's primary atomic clock CS2 furnishes the second intervals of legal time (CET and CEST) with the aid of which all radio-controlled clocks in Germany are controlled via a long-wave transmitter in Mainflingen near Frankfurt. (Photo: PTB)
  • The first cesium fountain CSF1 of PTB (1.2 MB) Since the year 2000, the first cesium fountain CSF1 of PTB has contributed to the realization of International Atomic Time. In this clock, cesium atoms are laser-cooled down to 2 μK and run on a ballistic trajectory to achieve the longest possible request time. (Photo: PTB)
  • Transmission mast of DCF77 (1.7 MB) Transmission mast of DCF77 in Mainflingen, south-east of Frankfurt/Main. The time signal cannot be received with normal longwave radios – but with "radios for the time": Radio-controlled clocks deliver the official time "wireless" to everyone who wants to have it to his home or his wrist. (Photo: PTB)
  • PTB's cesium fountain CSF1 (1.2 MB) PTB physicist Stefan Weyers at the first cesium fountain CSF1 of PTB which was put into operation in 1999. Since 2005, it has a "colleague", CSF2. (Photo: PTB)
  • The propagation distance of the transmitter DCF7 (1.1 MB) The propagation distance of the transmitter DCF77 is approx. 2000 km. In some cases, signals have, however, even been received in Australia. (Image: PTB)
  • Optical ytterbium clock at PTB (0.9 MB) Optical atomic clock on the basis of a stored ytterbium ion: Electrode system of the ion trap developed at PTB. (Photo: PTB)

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AmpereAmpere

  • Josephson voltage standard from PTB (667 kB) Josephson voltage standard from PTB with approx. 70 000 series-connected tunnel elements, generating together 10 volts. (Photo: PTB) Or: Programmable 10-volt Josephson circuit from PTB. (Photo: PTB)
  • Quantum Hall device (737 kB) Quantum Hall device (in a sample carrier) for the reproduction of the unit of resistance. The device consists of semiconductor hetero-structures which are manufactured by molecular beam epitaxy in PTB's Clean Room Center. (Image: PTB)
  • PTB's molecular beam epitaxy machine (1.1 MB) PTB's molecular beam epitaxy machine used to manufacture semiconductor quantum standards such as quantum Hall resistors. (Photo: PTB)
  • Graphene oven (1.1 MB) For the simplification of resistance metrology, the material graphene, which was discovered only a few years ago, offers a great potential. Graphene is a single-layer network of carbon atoms which shows the quantum Hall effect at higher temperatures and lower magnetic fields than the Ga/Al arsenide structures presently used for quantum Hall resistors. Research activities of the past few years have shown that graphene produced from SiC is suited best for metrological applications. Therefore, an apparatus for the manufacture of graphene from SiC has been established in the Clean Room Centre of PTB (Photo: PTB)
  • On this silicon chip, Klaus von Klitzing discovered the quantum Hall effect (2.0 MB) It is already a museum piece: On this silicon chip, Klaus von Klitzing discovered the quantum Hall effect (Photo: PTB)
  • The quantum metrology triangle (278 kB) The quantum metrology triangle shows the relations between the three electrical units volt, ohm and ampere and the involved fundamental constants. To close the triangle, only the ampere, as the last of the three units, must be placed on the basis of a fundamental constant (the charge of an electron). (Image: PTB)
  • Bridge building in the nanocosmos (771 kB) Bridge building in the nanocosmos – towards a quantum standard for the ampere. (Photo: PTB)
  • Transistor structures (377 kB) Counting of single electrons? Yes, with these transistor structures. (Photo: PTB)
  • Semiconductor single electron (SET) pump (80 kB) Electron-microscopic image of a semiconductor single electron (SET) pump: Gate electrodes (violet, yellow) cross a small conducting track made of semiconductor material (green). (Image: PTB)
  • Semiconductor structure (1.0 MB) This semiconductor structure can measure single electrons and their charge. Four pumps are integrated onto the chip; each of them has three gate electrodes (yellow) crossing a semiconductor wire (blue). The pumped electrons are detected with the aid of three single-electron detectors (gray). (Image: PTB)
  • A chip with a SET (Single-Electron-Tunneling) circuit (674 kB) A chip with a SET (Single-Electron-Tunneling) circuit, installed in the sample holder. The window of the printed circuit card allows the circuit to be contacted by means of the contact pad which is visible above it. (Image: PTB)
  • Franz Josef Ahlers at and in an experiment for quantum electronics (1.1 MB) Man-machine communication at PTB: The scientist Franz Josef Ahlers at and in an experiment for quantum electronics. (Photo: PTB/original-okerland)

KelvinKelvin

  • triple point cell (1.2 MB) This is how the SI base unit kelvin has so far been defined: on the basis of the triple point of water. This is the temperature at which water occurs in all three phases: solid, liquid and gaseous. The photo shows a triple point cell. (Photo: PTB)
  • PTB's gas thermometer for the redefinition of the kelvin (1.1 MB) Core piece of PTB's gas thermometer for the redefinition of the kelvin: Four pressure cylinders of stainless steel accommodate the different capacitors for the measurement of the dielectric gas constant (Fig.: PTB)
  • Cavity radiator at PTB (873 kB) A modern high-temperature cavity radiator at PTB which reaches temperatures up to 3000 °C (Photo: PTB)
  • Blackbody radiator at PTB (867 kB) (Photo: PTB/original-okerland)
  • Wolfram-Bandlampe (2.3 MB) Wolfram-Bandlampen dienen als Transfernormal für die Strahlungstemperatur und die spektrale Strahldichte.
  • Tungsten strip lamp (720 kB) Tungsten strip lamps serve as transfer standards for radiation temperature and spectral radiance. (Photo: PTB/original-okerland)
  • PTB's microkelvin facility (1.5 MB) This microkelvin facility allows temperatures of only a few millionths of a kelvin to be generated above absolute zero – for the investigation of low-temperature phenomena in condensed matter. (Photo: PTB/original-okerland)
  • The new kryostat (10.9 MB) The new cryostat (in the Temperature Department) for the realization and dissemination of the Provisional Low-Temperature Scale PLTS-2000 for the temperature range from 0.9 mK to 1 K. PTB is the only metrology institute worldwide which offers calibrations of thermometers in this temperature range. (Photo: PTB)
  • Infrared camera image (672 kB) Seeing heat – this is possible with infrared cameras. An infrared camera provides an image which is distributed according to temperature zones. How high is the smallest detectable temperature difference? This is one of the questions which are posed when decisions about the quality of these cameras are made. PTB calibrates thermography cameras with the aid of cavity radiators. After that it is guaranteed that the camera is in a position to exactly determine temperature values in a defined temperature range. (Photo: PTB)
  • Thermographic image (104 kB) Thermographic image of the Siemens building at PTB's Berlin institute. (Photo: PTB)
  • Temperature characteristic of a resistance thermometer (1.1 MB) Everyday life in the laboratory for applied thermometry: A PTB employee records the temperature characteristic of a resistance thermometer. (Photo: PTB/original-okerland)
  • [Translate to English:] Sammlung von Thermometern (1.0 MB) [Translate to English:] Glasthermometer sind nach wie vor für manche Temperaturmessungen im Alltag gebräuchlich. Noch werden sie anhand einer Temperaturskala kalibriert, deren Einheit über den Tripelpunkt des Wassers definiert ist. In Zukunft wird es eine Naturkonstante sein, nämlich die Boltzmannkonstante. (Abb.: PTB/original-okerland)

CandelaCandela

  • Hefner candle (1.3 MB) From 1896 to 1941, the "Hefner candle" was used as a state-approved standard for the unit of luminous intensity in Germany, Austria and in Scandinavia. Candela literally means "candle". The Hefner candle furnishes a flame with always the same properties and with an uncertainty of 1.5 %. (Photo: PTB)
  • "Hefner candle" (1.7 MB) From 1896 to 1941, the "Hefner candle" was used as a state-approved standard for the unit of luminous intensity in Germany, Austria and in Scandinavia. Candela literally means "candle". The Hefner candle furnishes a flame with always the same properties and with an uncertainty of 1.5 %. (Photo: PTB)
  • Standard lamp (0.9 MB) In the times prior to using cryogenic radiometers, the standard lamp was indispensible. It glowed only approx. 20 minutes per year. PTB had 23 of these national standards for the unit of luminous intensity "candela" at its disposal to calibrate other lamps or photometers with it. (Photo: PTB)
  • Cryogenic radiometer (644 kB) From the satellite-based remote sensing instrument to the exposure facility of the semi-conductor industry, from color measurements to radiation thermometry: reliable measurements of the radiant power of light sources require the determination of the spectral responsivity of radiation detectors. For this purpose, absolute measuring primary detector standards are used. The sensitivity of a radiation detector at different wavelengths is obtained by a comparison measurement (calibration) against a primary standard or a reference receiver which has already been calibrated. As primary standards, PTB uses in the spectral ranges from the long-wave infrared or terahertz radiation to short-wave X-rays so-called cryogenic radiometers. These are thermal detectors which are operated at a very low temperature (–269 °C) and whose core piece is a radiation absorber. These cryogenic radiometers allow best relative measurement uncertainties clearly below 0.01 % to be achieved in radiant power measurements. (Photo: PTB)
  • Cryogenic radiometer (373 kB) Cryogenic radiometer in PTB's Clean Room Center. (Photo: PTB)
  • Ti:Sa laser (253 kB) Ti:Sa lasers with frequency doubling in TULIP design (with tunable wavelength) for the calibration of the irradiance sensitivity of photometers and radiometers in the short-wave and long-wave spectral range. (Photo: PTB)
  • PTB's goniophotometer (1.0 MB) PTB's goniophotometer is unique worldwide. With three long-armed robots and especially developed photometer heads, the device can determine photometric, radiometric and colorimetric quantities simultaneously and in a spectrally integrating way. At the same time, it can determine relative spectral distributions with the aid of a CCD array spectrometer. (Photo: PTB)
  • PTB's goniophotometer (1.0 MB) PTB's goniophotometer is unique worldwide. With three long-armed robots and especially developed photometer heads, the device can determine photometric, radiometric and colorimetric quantities simultaneously and in a spectrally integrating way. At the same time, it can determine relative spectral distributions with the aid of a CCD array spectrometer. (Photo: PTB)
  • Integrating sphere (1.7 MB) The largest integrating sphere of PTB has a diameter of 2.50 m and serves to measure spatially distributed photometric quantities such as, for example, light flux or partial light fluxes. (Photo: PTB)
  • Measuring facility of PTB for the evaluation of the service life of organic light-emitting diodes (OLEDs) (1.2 MB) Measuring facility of PTB for the evaluation of the service life of organic light-emitting diodes (OLEDs). (Photo: PTB)
  • Leuchtdioden-Transfernormal (7.4 MB) In der PTB entwickeltes Normal für Höchstleistungsleuchtdioden. (Abb.: PTB)

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Consumer Protection

Consumer ProtectionConsumer Protection

  • Thomas Kleine-Ostmann makes microwaves visible (1.2 MB) Thomas Kleine-Ostmann makes microwaves visible – for demonstration purposes. To this end, he conducts them through a lens made of paraffin (Photo: original-okerland)
  • Microwave measuring instrument (1.3 MB) Reiner Pape with a microwave measuring instrument (Photo: original-okerland)
  • Measurements for electromagnetic compatibility (1.2 MB) As a provider of metrological services, PTB performs several thousands of calibrations and tests every year. Photo: Measurements for electromagnetic compatibility. (Photo: PTB)
  • Ignition of an air-gas mixture (537 kB) Safety engineering is a top priority at PTB (and not only in explosion protection). The photos shows the ignition of an air-gas mixture by laser radiation. (Photo: PTB)
  • Explosion (1.1 MB) Each highly technical society is also a society at risk. Reliable metrology is needed to recognize these risks and to minimize them. In Germany, PTB provides the metrological basis for monitoring (Photo: PTB)
  • Visitors' group in PTB's reverberation room (2.6 MB) All six (!) walls in PTB's reverberation room are designed in such a way that each incident sound is not reflected as usual, but is almost completely "swallowed". In this way, sound level measuring instruments and microphones can be acoustically tested free from room influences. Sound level measuring instruments are the most important measuring instruments for the measurement of noise. Noise impairs the quality of life, can cause health problems for people and leads to considerable costs. (Photo: original-okerland)
  • "Artificial ears" (2.7 MB) Even if you can no longer hear, PTB's services are required: The regular checking of audiometers is made possible by the provision and testing of "artificial ears" through PTB. (Photo: PTB)
  • PTB's reverberation room (868 kB) PTB's reverberation room: The rotating screen makes sure that the sound of a noise source is distributed in the room as uniformly as possible. (Photo: PTB)
  • Measurements in the reverberation room (1.7 MB) Heinrich Bietz with a measuring instrument in the reverberation room of PTB. The rotating screen behind him ensures that the sound of a noise source is distributed in the room as uniformly as possible. (Photo: original-okerland)
  • PTB's 2 MN force standard machine (1.6 MB) The fact that force measurements have something to do with safety becomes particularly evident when carrying out crash tests with dummies. The force which acts on the dummy in the case of a simulated accident is determined by force transducers everywhere on the dummy's body. These devices are checked at regular intervals by the automobile companies in their calibration laboratories. The force calibration machines used for this purpose can be traced back directly to the standards of PTB. The photo shows the largest force standard machine of PTB, which works with direct deadweight effect: the 2 MN force standard machine. (Photo: PTB)
  • PTB's 2-meganewton force standard machine (1.2 MB) It is the colossus among PTB's force measuring machines: The 2-meganewton force standard machine extends over three floors (the image is composited graphically here). It contains heavy-weight plates of several tons – the reason for its enormous dimensions. The exterior of its even stronger sister, which can measure loads of up to 16.5 meganewtons, is by far less impressive, because in her case, the force is transmitted hydraulically. (Photo: PTB)
  • Air dust collector (2.6 MB) At PTB, this air dust collector is used to continuously check the air dust for possible radioactive loads. It is part of Germany's nationwide measuring and information system (IMIS) which was established after the nuclear accident in Chernobyl. With the aid of this measuring system it came to light that radioactive hospital waste had one day been burnt by mistake in a furnace in Gibraltar. (Photo: PTB)
  • "Water phantom" of PTB (1.9 MB) View into the "water phantom" of PTB. In this water calorimeter, three sensors – one round one and two pin-shaped ones – are located which are called "ionization chambers". They are calibrated here to calibrate, in turn – at a later date – irradiation devices in hospitals. Only on an irradiation device tested in this way can the physician in charge adjust the exact treatment dose. (Photo: PTB)
  • Wheel loader balance (1.7 MB) At PTB, measuring instruments are tested by statutory mandate – also the wheel loader balances shown in the photo. (Photo PTB)

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