This paper discusses an optical position sensor which can be used in balances based on the principle of electromagnetic force compensation (short used EFC) for example. Other applications are zero point detection as well as high precision positioning in the range of ± 200 μm. The position sensor consists of two infrared-LED (IR-LED) which illuminate a single photodiode via an aperture. The aperture is movable and performs a shadowing of the beams, thus shadowing changes due to the position of the aperture. The photodiode detects light from both LED. Both light sources have to be modulated and phase shifted to distinguish them in the photodiode signal. The evaluation of the position of the aperture is done by demodulating the received signal.
A major advantage of this method is that the aperture's operating point is in the centre of the beams. Hence higher sensitivity is achievable and the beams can be focused onto the photodiode. Furthermore standard components are used and thus expensive differential photodiodes are no longer necessary.

Surface roughness is one of many parameters that influences on mass stability of standard weight, commonly used as a transfer standard of mass SI unit. One of the most famous non-invasive methods for determining surface roughness from a surface profile of material is a vertical scanning interferometry (VSI) with a white light source. In this research, 3-D surface profiles of 316-stainless steel, usually used as a material for standard weights, are constructed by using VSI, based on Michelson interferometer (MI). Because of its low-coherent properties, low cost, and compact light source, a superluminescent diode (SLD) is chosen as a low-coherence light source in our interferometry system. Since a continuous wavelet transform (CWT) algorithm provides accuracy results, it is also used as a numerical analyzing method for the interferogram signals, taking from our VSI. The surface roughness and measurement uncertainty, calculated from the constructed 3-D surface roughness profiles of 316-stainless steel samples, are discussed.

Gas leak detection is getting more important in the last years. Primary standards for leaks can be divided into sensitive and insensitive to gas species. The method proposed by authors is insensitive to gas species. The basic principle of the method is mass comparison and detection of the difference between standard weight and the leak to be calibrated. The authors made several measurements to prove the repeatibility of the method. It can be seen that to get results with reasonable uncertainty the weekend measurement is sufficient.

In order to further improve the metrological properties of weighing systems based on the principle of electromagnetic force compensation (EMFC) as well as quality assurance, it is necessary to determine the parameters relevant for the dynamic operation, such as measurement time and controller behavior. This determination is carried out by loading the balance system and observing the indication. Typically this is done by a load changer using different metrological weights. This method is inevitable if metrological traceability is required. However, the conventional procedure of load changing also entails several disadvantages. The number of possible load changes per unit time is limited and the force characteristic during loading is usually unknown and relatively difficult to reproduce or manipulate. Furthermore the fast and sudden exchange of the weights causes mechanical vibrations and a movement of the surrounding air, both of which act as additional disturbances.
In this paper we propose an alternative loading method, with which these shortcomings can be improved and compare it to a conventional system. This method is based on loading the weighing system in a defined manner using a Lorentz-force, allowing the tester to generate a known, virtually arbitrary force characteristic during loading.
It is shown that the Lorentz-force generated load represents a practical alternative to classical weights, offering advantages in reproducibility, dynamics and ability to be automated. Since the proposed method applies a known Lorentz-force to the weighing system it becomes possible to exactly determine the relationship between the force acting on the weighing pan and the resulting behavior of the weighing system.

This paper shows an interesting case for a national comparison where two transfer standards have been used. Participating laboratories have calibrated one transfer standard or the other, but one that calibrated both, so that can be used as a link to make a joint evalution for all the participant laboratories.