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In this paper, a miniaturized weighing cell that is based on a micro-electro-mechanical-system (MEMS) is discussed. The MEMS-based weighing cell is inspired by macroscopic electromagnetic force compensation (EMFC) weighing cells and one of the crucial system parameters, the stiffness, is analyzed. The system stiffness in the direction of motion is first analytically evaluated using a rigid body approach and then also numerically modeled using the finite element method for comparison purposes. First prototypes of MEMS-based weighing cells were successfully microfabricated and the occurring fabrication-based system characteristics were considered in the overall system evaluation. The stiffness of the MEMS-based weighing cells was experimentally determined by using a static approach based on force-displacement measurements. Considering the geometry parameters of the microfabricated weighing cells, the measured stiffness values fit to the calculated stiffness values with a deviation from -6.7 to 3.8% depending on the microsystem under test. Based on our results, we demonstrate that MEMS-based weighing cells can be successfully fabricated with the proposed process and in principle be used for high-precision force measurements in the future. Nevertheless, improved system designs and read-out strategies are still required.

Since the turn of the millennium, the development and commercial availability of optical frequency combs has led to a steadily increase of worldwide installed frequency combs and a growing interest in using them for industrial-related metrology applications. Especially, GPS-referenced frequency combs often serve as a "self-calibrating" length standard for laser wavelength calibration in many national metrology institutes with uncertainties better than u = 1 × 10^-11. In this contribution, the application of a He-Ne laser source permanently disciplined to a GPS-referenced frequency comb for the interferometric measurements in a nanopositioning machine with a measuring volume of 200 mm × 200 mm × 25 mm (NPMM-200) is discussed. For this purpose, the frequency stability of the GPS-referenced comb is characterized by heterodyning with a diode laser referenced to an ultrastable cavity. Based on this comparison, an uncertainty of u = 9.2 × 10^-12 (τ = 8 s, k = 2) for the GPS-referenced comb has been obtained. By stabilizing a tunable He-Ne source to a single comb line, the long-term frequency stability of the comb is transferred onto our gas lasers increasing their long-term stability by three orders of magnitude. Second, short-term fluctuations-related length measurement errors were reduced to a value that falls below the nominal resolving capabilities of our interferometers (ΔL/L = 2.9 × 10^-11). Both measures make the influence of frequency distortions on the interferometric length measurement within the NPMM-200 negligible. Furthermore, this approach establishes a permanent link of interferometric length measurements to an atomic clock.

We present a new method for traceable calibration of size and form error of microspheres, which was realised by stitching a series of atomic force microscopic (AFM) images measured at different orientations of microspheres using the metrological large range AFM of the PTB. The stitching algorithm is achieved using an iterative closest point point-to-plane algorithm. As the AFM tip geometry is one of the most significant error sources for the developed method, it was traceably calibrated to a line width standard (type IVPS100-PTB), whose feature geometry was calibrated with a traceable route to the lattice constant of crystal silicon. Measurement setup, scan strategy, and data evaluation processes have been detailed in the paper. Measurement results show high stability and robustness of the developed method. For instance, the standard deviation of four repeated measurements reaches 5 nm, indicating promising performance.

The aim of this work was to validate a novel methodology for high-resolution, repetitive measurements of mass dynamics of biological processes and structures in a closed plant-earth ecosystem consisting of Mammillaria vetula and microorganisms. To perform these experiments, the living system was materially welded into a newly developed Titanium Weighing Hollow Body (TWHB) with a laser. Three non-vital, also hermetically welded and high-vacuum suitable, externally identical TWHBs, filled with sand, served as controls. All TWHBs were equipped with a feedthrough and integrated light source. LEDs generated continuous light in all four bodies, which drove the photobiological processes in the vital test body and allowed long-term growth. Mass differences of the TWHBs were measured with a vacuum mass comparator at four points in time three months apart against two stainless steel mass standards. The expanded measurement uncertainty of the mass increase of the vital TWHB was calculated according to the Guide to the Expression of Uncertainty in Measurement (GUM) in each of the three independent experiments. The mass gain of the vital over the three nonvital TWHBs over the total experimental period of 9 months was +18 μg with the expanded measurement uncertainty 30 μg. The resulting mass gain would have had to be > 48 μg to be considered statistically significant with a confidence level of 97.7%; time intervals over three and six months were also not significant. The study validates for the first time a methodology capable of measuring mass dynamics of living matter over time, when statistically sound conclusions with measurement uncertainties in the microgram range are required. This opens up a new level of precision mass measurements, which makes the methodology a candidate, e.g., for the verification of the principle of mass conservation in the life-sciences.

Thermometer zur Überwachung, Steuerung oder Regelung der Prozesstemperatur werden in der Verfahrenstechnik in verschiedensten Medien wie strömenden Gasen, verschiedenen Ölen, Wasser bis hin zu Heißdampf und auch in verschiedenen Temperaturbereichen eingesetzt. In Abhängigkeit von den Mediumsbedingungen verändern sich die Wärmeübergangskoeffizienten beim Wärmeaustausch zwischen Medium und Thermometer. Als Folge dessen sind sowohl die statisch-thermischen Messabweichungen als auch die dynamischen Kennwerte dieser Thermometer neben ihrem Aufbau auch von den Mediumsbedingungen abhängig. Um schnell auf Änderungen der Mediumstemperatur reagieren zu können, ist es wichtig, die dynamischen Eigenschaften von Thermometern im Vorfeld des Einsatzes abzuschätzen. Das kann durch numerische Berechnungen erfolgen, die jedoch zum Teil sehr aufwändig oder auch zu ungenau sein können, wenn Mediumseigenschaften, Strömungsbedingungen oder geometrische Details der Messstelle nicht genau bekannt sind. Deshalb ist es meist genauer, die dynamischen Eigenschaften experimentell unter bekannten Bedingungen zu bestimmen. Thermometer können sich in ihren Ausführungen sehr stark unterscheiden. Thermometer für Messungen in Gasen haben häufig freiliegende Sensoren, die mit einem Schaft fixiert sind. Für Messungen in Flüssigkeiten oder Schüttgütern werden geschlossene Bauformen mit innenliegenden Sensoren verwendet., die bei hohen mechanischen oder chemischen Belastungen zusätzlich in Schutzrohren eingebettet sein können.