The producer of high-precision measurement equipment for strain gauges has to guarantee that the physical unit mV/V is to be presented exact, stable, but also easy to use. This is achieved by means of calibration standards, which are checked regularly by the PTB. A further certainty is attained through companyinternal comparisons.
In the following will be shown which technical conditions and limits are to be observed, and which problems are arising, if one wants to reach transferable results down to some ppm.

Squeeze air bearings are based on a phenomenon known as the squeeze effect, which causes a pressured air film with relative perpendicular oscillation between two planes. The aim of this study is to achieve non-contact active motion error correction with squeeze effect. Hence, it has ability to be operated even if no pressured air supply and no relative sliding motion between them. The experimental device has piezo-driven oscillating pads and central rotating shaft. Piezos are controlled by two kinds of signals. One is the sinusoidal signal stimulate the squeeze motions. The other is the operation signal, which controls the floating shaft movement by the travel of oscillating pads. Therefore, application of a controllable pattern on piezos allows the shaft to be manipulated in the multi degreeof- freedom. The run-out of shaft was reduced from 8.1 um to 2.4 um and variation of attitude became to be undetectable. The run-out was improved by decreasing the clearance between shaft and pads by increasing the air film stiffness. Applying the feedback control to make the device more accurate, the run-out was reduced successfully.

Correct guiding is of major importance in the operation of belt conveyors. Faults such as incorrect geometry, uneven load distribution or belt splicing cause lateral movement of the running belt. The running behaviour of the belt is largely dependent on its deformation at the point where it meets the drums. For precise automatic control, it is necessary to know the belt position, the inclination between drum and running direction and the curvature of the belt at this point. This data is also necessary in order to check the accuracy of the mechanical models developed to simulate the running behaviour of the belt. This paper deals with the lateral running behaviour of the belt on a skewed tail pulley as well as a conical tail pulley. Belt deformations were recorded by a CCD camera as well as by conventional potentiometer distance sensors. The resultant measurements were compared with the mechanical models.

The present paper is focused on some experimental measurements concerning forces appearing at contact between wheel and rail during the rolling process. Experiments have been performed for real working conditions on a railway testing circuit located near Bucharest. Strain gauge measurements have been preferred in order to estimate some typical parameters for the safety of the rolling process.

In the paper a new portable battery operated exciter dedicated for the calibration of the mechanical vibration sensors (transducers) is presented. This instrument is based on the Motorola’s digital signal processor DSP 56167 which is quite new approach to the construction of such instrument. The DSP with the reference sensor used as an information source about the generated vibration signals constitutes the measurement system. This system is used for the generation of the reference mechanical vibrations. The digital approach to the calibration ensures the new level of the performances. Programmability of the generated vibration amplitude, frequency accuracy and the level of total harmonic distortions (THD) overcomes all other designs available on the market.