Surface plates are used in the industry and measurement laboratories for performing measurements of length, angles and deviations of form and position of measured subjects, for checking and control of measurement bars and rulers. Our aim is to perform a calibration of the surface plate without involving either interferometric system or autocollimator, which would be too expensive, therefore using only electronic levels. And even when the appropriate device for calibration is chosen, the decision between many different types of algorithms has to be made. On top of all, traceability of measurement must be also assured. Research work in this field, represented in this article, is focused mainly on assuring the calibration traceability of results when performing measurements of flatness with electronic levels. Traceability is assured with accurate sine bar SL001, developed in our laboratory especially for purposes of very precise calibrations.

Following the Guide to the Expression of Uncertainty in Measurement (GUM) and other recent documents on uncertainty, we analyse typical measurement situations met in a set of Measurement Systems: measurement modelling and comparison, calibration and traceability of measuring devices, dissemination model and interlaboratory comparison, test of measurement compatibility, evaluation of dissemi-nation processes, improved evaluation methods of interlaboratory comparisons.

The authors’ laboratory is accredited for calibration by comparison of contact thermometers and calibration baths and furnaces in the range from -55 °C to 1250 °C. The accreditation was granted to the laboratory in January 1997 as the first temperature calibration laboratory in Slovenia. It also became a holder of national standards for thermodynamic temperature thus providing the traceability of temperature in Slovenia. There are many thermometers and relative humidity sensors made combined as thermo-hygrographs. These applications serve mainly for monitoring environmental conditions at various places. Their users usually need to know their performance therefore they need calibration certificates of an accredited laboratory for these thermo-hygrographs as an evidence of traceability. Since there are quite a few demands to calibrate both a temperature and a humidity sensor, and there is no other laboratory accredited for calibration of relative humidity sensors in Slovenia, we have decided to set-up the facility for calibration of small relative humidity sensors. The decision based also on relative affinity between thermodynamic temperature and relative humidity.

In accordance with ISO 17025, measuring and test equipment, including gear and spline artefacts must have been traced back to recognized national or international primary standards through an unbroken traceability chain. This is the reason why there have been national gear standards and gear standard measuring equipment in Germany since the sixties, for example for the elements: profile, helix, pitch, radial run-out of gearings and roughness. In contrast to this, no direct link-up to spline artefacts has so far been made at the PTB for splines. If one proceeded in compliance with the DKD traceability criteria applicable to other geometrical measurands within the DKD, a large number of PTB calibrations against the PTB's reference standards or comparison measurements of spline gauges with the PTB would have to be performed, of course at relatively high cost. In this lecture, the most recent traceability strategies for different levels will be discussed.
By bringing up this topic, the author aims to point out that one should start thinking about the necessity of defining traceability criteria within the meaning of ISO 17025, which are uniform all over the world so that mutual recognition of the measurement results for gears and splines can be achieved on the international level.

Paper presents two classes of unconventional measurement signals with special, designed shapes, in context of their application for the identification measurements. Firstly, measurement idea, choosing proper observables and signal shape design principle are explained. In the next part of the paper mirror signals (power and Poisson) and polynomial signals (Chebyshev, Legendre) are presented. An example illustrating practical applications of polynomial signals is included.